ATMXT1664S1-CU031 [MICROCHIP]
Analog Circuit, 1 Func, PBGA128;
| 型号： | ATMXT1664S1-CU031 |
| 厂家： | 
MICROCHIP |
| 描述： | Analog Circuit, 1 Func, PBGA128 |
| 文件： | 总92页 (文件大小：2260K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Features
• maXTouch® Touchscreen
– Two touchscreens with true 12-bit multiple touch reporting and real-time XY
tracking for up to 16 concurrent touches per touchscreen
– Screen sizes 8 – 12.1 inches diagonal supported at 5 mm electrode pitch.
• Number of Channels
– Electrode grid configurations of up to 32 X and 52 Y lines supported
– Touchscreens up to 1664 channels (subject to other configurations)
– Up to 32 channels can be allocated as fixed keys (subject to other configurations)
• Signal Processing
maXTouch®
1664-channel
Touchscreen
Controller
– Advanced digital filtering using both hardware engine and firmware
– Self-calibration
– Auto drift compensation
– Adjacent Key Suppression® (AKS®) technology
– Noise cancellation algorithms for display noise suppression
– Grip suppression and suppression of unintentional touches
– Down-scaling and clipping support to match LCD resolution
– Ultra-fast start-up and calibration for best user experience
– Supports axis flipping and axis switch-over for portrait and landscape modes
– Fast and powerful 32-bit processor core
mXT1664S1
Revision 2.0
– Supports baseline reference data for better calibration
– Supports lens bending algorithms to restore signal distortions
• Scan Speed
– Maximum single touch >250Hz, subject to configuration
– Maximum 16 touches >100Hz, subject to configuration
– Configurable to allow power/speed optimization
– Programmable timeout for automatic transition from active to idle states
• Response Times
– Initial latency <15 ms for first touch from idle, subject to configuration
• Sensors
– Works with PET or glass sensors, including curved profiles
– Works with all proprietary sensor patterns recommended by Atmel®
• Stylus Support
– Supports passive stylus with 2 mm contact diameter, subject to configuration
– Supports Atmel maXStylus™, subject to configuration
• Environmental Conditions
– Operating temperature –40°C to +85°C
– Moisture tolerance good
• Panel Thickness
– Glass up to 2.5 mm, screen size dependent
– Plastic up to 1.2 mm, screen size dependent
• Interfaces
– I2C-compatible slave mode; Standard/Fast Mode: up to 400 kHz, High speed mode:
up to 1.7 MHz
– USB 2.0-compliant composite device, full speed (12 Mbps)
– HID-I2C interface for Microsoft® Windows® 8
9871EX–AT42–12/13
• Power
– Digital 1.8 V (I2C-compatible mode only) or 2.7 V to 3.3 V nominal
– Analog 2.7 V to 3.3V nominal
– High voltage X line drive 2.7 V to 10.0 V nominal
• Packages
– 128-ball VFBGA 7 × 7 × 1 mm, 0.5 mm ball pitch
2
mXT1664S1
9871EX–AT42–12/13
mXT1664S1
1. Overview of the mXT1664S1
1.1
Introduction
The Atmel maXTouch family of touch controllers has set a new industry benchmark for
capacitive touchscreens with their low current consumption, fast response time and high levels
of accuracy. The mXT1664S1 single-chip solution offers the benefits of the maXTouch
enhanced architecture on devices with touchscreens up to 14 in. diagonal:
• Patented capacitive sensing method – The mXT1664S1 uses a unique charge-transfer
acquisition engine to implement the Atmel-patented QMatrix® capacitive sensing method.
This allows the measurement of up to 1664 mutual capacitance nodes. Coupled with a
state-of-the-art CPU, the entire touchscreen sensing solution can measure, classify and
track individual finger touches with a high degree of accuracy.
• Capacitive Touch Engine (CTE) – The mXT1664S1 features an acquisition engine, which
uses an optimal measurement approach to ensure almost complete immunity from
parasitic capacitance on the receiver inputs (Y lines). The engine includes sufficient
dynamic range to cope with anticipated touchscreen mutual capacitances, which allows
great flexibility for use with the Atmel proprietary ITO pattern designs. One and two layer
ITO sensors are possible using glass or PET substrates.
• Noise filtering – Hardware noise processing in the capacitive touch engine provides
enhanced autonomous filtering and allows a broad range of noise profiles to be handled.
The result is good performance in the presence of charger and LCD noise.
• Processing power – The main CPU has two powerful, yet low power, microsequencer
coprocessors under its control. These combine to allow the signal acquisition,
preprocessing, postprocessing and housekeeping to be partitioned in an efficient and
flexible way. This gives ample scope for sensing algorithms, touch tracking or advanced
shape-based filtering. An in-circuit reflash can be performed over the chip’s hardware-
driven interface.
• Interpreting user intention – The Atmel mutual capacitance method provides
unambiguous multitouch performance. Algorithms in the mXT1664S1 provide optimized
touchscreen position filtering for the smooth tracking of touches. Stylus support allows
stylus touches to be detected and distinguished from other touches, such as finger
touches. The suppression of unintentional touches from the user’s gripping fingers, resting
palm or touching cheek or ear also help ensure that the user’s intentions are correctly
interpreted.
1.2
Understanding Unfamiliar Concepts
If some of the concepts mentioned in this datasheet are unfamiliar, see the following sections
for more information:
• Appendix C on page 81 for a glossary of terms
• Appendix D on page 82 for QMatrix technology
3
9871EX–AT42–12/13
1.3
Resources
The following datasheet provide essential information on configuring the device:
• mXT1664S 2v0 Protocol Guide
The following documents may also be useful (available by contacting Atmel’s Touch
Technology Division):
• Configuring the device:
– Application Note: QTAN0058 – Rejecting Unintentional Touches with the
maXTouch Touchscreen Controllers
– Application Note: QTAN0078 – maXTouch Stylus Tuning
• Miscellaneous:
– Application Note QTAN0050 – Using the maXTouch Debug Port
– Application Note QTAN0061 – maXTouch™ Sensitivity Effects for Mobile Devices
– Application Note QTAN0086 – Touchscreen Design for Gloved Operation
• Touchscreen design and PCB/FPCB layout guidelines:
– Application Note QTAN0054 – Getting Started with maXTouch Touchscreen
Designs
– Application Note QTAN0094 – mXT1664S PCB/FPCB Layout Guidelines
– Application Note QTAN0080 – Touchscreens Sensor Design Guide
• Other documents – The device uses the same core technology as the mXT768E, so the
following documents may also be useful (available by contacting the Atmel Touch
Technology division):
– Application Note: QTAN0083 – mXT768E Power and Speed Considerations
– Application Note QTAN0052 – mXT224 Passive Stylus Support
4
mXT1664S1
9871EX–AT42–12/13
mXT1664S1
2. Pinout and Schematic
2.1
Pinout Configuration
N
X31
X28
X26
VDDUSB
GND
RESET
SDA
VDD
I2CMODE
VDD
NC
VDDCORE
GND
GPIO1
GPIO0
X15
X14
M
L
X29
X30
X27
GND
VDD
SCL
XOUT
XIN
GND
CHG
Reserved CHRG_IN
X13
X10
X12
XVDD
USBDM VDD_INPUT
DBG_DATA
X11
XVDD
USBDP
DBG_CLK
COMMSEL
K
J
GND
X22
X24
X21
X23
X9
X7
X8
X6
GND
X5
GND
H
G
F
X20
X17
X19
X18
X16
SYNC(TDI) INDICATION ADDSEL
X4
X1
X3
X2
X0
XVDD
X25
Y44
GND
Y23
XVDD
Y41
Y38
Y40
Y37
Y39
Y36
Y43
Y10
Y13
Y9
Y8
E
D
C
Y12
Y11
GND
Y35
Y31
Y34
Y28
Y15
Y5
AVDD
GND
Y14
Y0
AVDD
Y51
Y50
GND
Y47
Y46
Y42
Y20
Y21
Y18
Y16
B
A
Y33
Y30
Y27
AVDD
Y24
GND
AVDD
Y6
Y3
Y1
Y32
Y29
Y26
Y49
Y48
Y45
Y25
Y22
Y19
Y17
Y7
Y4
Y2
1
2
3
4
5
6
7
8
9
10
11
12
13
Bottom View
5
9871EX–AT42–12/13
2.2
Pinout Descriptions
Table 2-1.
Ball
A1
Pin Listing
Name
Y32
Y29
Y26
Y49
Y48
Y45
Y25
Y22
Y19
Y17
Y7
Type
Comments
If Unused, Connect To...
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
–
I
I
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Analog power
A2
A3
I
A4
I
A5
I
A6
I
A7
I
A8
I
A9
I
A10
A11
A12
A13
B1
I
I
Y4
I
Y2
I
Y33
Y30
Y27
Y50
AVDD
Y46
Y24
Y21
GND
AVDD
Y6
I
B2
I
B3
I
B4
I
B5
P
I
B6
Y line connection
Y line connection
Y line connection
Ground
Leave open
Leave open
Leave open
–
B7
I
B8
I
B9
P
P
I
B10
B11
B12
B13
C1
Analog power
–
Y line connection
Y line connection
Y line connection
Analog power
Leave open
Leave open
Leave open
–
Y3
I
Y1
I
AVDD
Y31
Y28
Y51
GND
Y47
Y42
Y20
Y18
P
I
C2
Y line connection
Y line connection
Y line connection
Ground
Leave open
Leave open
Leave open
–
C3
I
C4
I
C5
P
I
C6
Y line connection
Y line connection
Y line connection
Y line connection
Leave open
Leave open
Leave open
Leave open
C7
I
C8
I
C9
I
6
mXT1664S1
9871EX–AT42–12/13
mXT1664S1
Table 2-1.
Ball
C10
C11
C12
C13
D1
Pin Listing
Name
Y16
Type
Comments
If Unused, Connect To...
I
I
Y line connection
Y line connection
Ground
Leave open
Leave open
–
Y5
GND
Y0
P
I
Y line connection
Ground
Leave open
–
GND
Y35
P
I
D2
Y line connection
Y line connection
Leave open
Leave open
D3
Y34
I
D11
D12
D13
E1
Y15
AVDD
Y14
I
P
I
Y line connection
Analog power
Leave open
–
Y line connection
Y line connection
Y line connection
Y line connection
Leave open
Leave open
Leave open
Leave open
Y38
I
E2
Y37
I
E3
Y36
I
E11
E12
E13
F1
Y13
Y12
Y11
Y41
Y40
Y39
I
I
I
I
I
I
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Y line connection
Leave open
Leave open
Leave open
Leave open
Leave open
Leave open
F2
F3
F6
F7
F8
Y44
Y43
Y23
I
I
I
Y line connection
Y line connection
Y line connection
Leave open
Leave open
Leave open
F11
F12
F13
G1
Y10
Y9
I
I
Y line connection
Y line connection
Y line connection
X matrix drive line
Leave open
Leave open
Leave open
Leave open
Y8
I
X17
O
X line drive voltage – see schematics in Section 2.3
on page 11
G2
G3
XVDD
X16
P
–
O
X matrix drive line
Leave open
G6
X25
O
X matrix drive line
Leave open
7
9871EX–AT42–12/13
Table 2-1.
Ball
Pin Listing
Name
Type
Comments
If Unused, Connect To...
G8
GND
P
Ground
–
G11
G12
X1
O
P
X matrix drive line
Leave open
–
X line drive voltage – see schematics in Section 2.3
on page 11
XVDD
G13
H1
X0
O
O
O
O
X matrix drive line
X matrix drive line
X matrix drive line
X matrix drive line
Leave open
Leave open
Leave open
Leave open
X20
X19
X18
H2
H3
H6
H7
H8
SYNC
I
O
I
External synchronization
Leave open
Leave open
Indicates a touch detected in a particular area of
INDICATION
ADDSEL (1)
the touchscreen. Refer to the mXT1664S 2v0
Protocol Guide for more information.
I2C-compatible address select
Leave open (USB mode)
H11
H12
H13
J1
X4
X3
O
O
O
O
O
P
X matrix drive line
X matrix drive line
X matrix drive line
X matrix drive line
X matrix drive line
Ground
Leave open
Leave open
Leave open
Leave open
Leave open
–
X2
X22
X21
GND
J2
J3
J11
J12
J13
K1
X7
X6
O
O
O
P
X matrix drive line
X matrix drive line
X matrix drive line
Ground
Leave open
Leave open
Leave open
–
X5
GND
X24
X23
K2
O
O
X matrix drive line
X matrix drive line
Leave open
Leave open
K3
K11
K12
K13
L1
X9
X8
O
O
P
X matrix drive line
X matrix drive line
Ground
Leave open
Leave open
–
GND
X26
O
X matrix drive line
Leave open
X line drive voltage – see schematics in Section 2.3
on page 11
L2
L3
XVDD
X27
P
Leave open
Leave open
O
X matrix drive line
8
mXT1664S1
9871EX–AT42–12/13
mXT1664S1
Table 2-1.
Ball
Pin Listing
Name
Type
P
Comments
If Unused, Connect To...
L4
VDD
Digital power
–
USBDP (1)
USB
USB device port data +
GND
L5
L6
Input: GND
Output: leave open
DBG_CLK
USBDM (1)
DBG_DATA
VDD_INPUT
XIN
I/O
USB
I/O
–
Debug clock
USB device port data -
Debug data
GND
Input: GND
Output: leave open
L7
L8
L9
For factory use only
VDD
External 16 MHz oscillator – only needed in USB
mode
I
Leave open
CHG (2)
OD
State change interrupt
Leave open (USB mode)
Selects communications interface:
I2C-compatible – connect to GND
USB (3) – connect to Vdd
L10
COMMSEL
I
–
L11
L12
X11
X10
O
O
X matrix drive line
X matrix drive line
Leave open
Leave open
X line drive voltage – see schematics in Section 2.3
on page 11
L13
XVDD
P
Leave open
M1
M2
M3
M4
M5
M6
M7
X28
X29
O
O
X matrix drive line
X matrix drive line
X matrix drive line
Ground
Leave open
Leave open
X30
O
Leave open
GND
VDD
VDD
SCL (1)
P
–
P
Digital power
–
P
Digital power
–
OD
Serial Interface Clock
Connect to VDD (USB mode)
External 16 MHz oscillator – only needed in USB
mode
M8
XOUT
O
Leave open
M9
M10
M11
M12
M13
N1
GND
Reserved
CHRG_IN
X13
P
–
Ground
–
Reserved for future use
Charger detect pin
X matrix drive line
X matrix drive line
X matrix drive line
Digital USB power
Ground
–
GND via 10 kΩ
Leave open
Leave open
Leave open
–
I
O
O
O
P
P
X12
X31
N2
VDDUSB
GND
N3
–
Reset low; has internal 20 kΩ to 60 kΩ pull-up
resistor
N4
RESET
I
Vdd (4)
N5
N6
SDA (1)
OD
I
Serial Interface Data
Connect to VDD (USB mode)
Leave open
I2CMODE
I2C-compatible protocol select (5)
9
9871EX–AT42–12/13
Table 2-1.
Ball
Pin Listing
Name
Type
Comments
If Unused, Connect To...
N7
Reserved
–
Reserved for future use
–
Digital core power. Must be connected as in
schematics (see Section 2.3 on page 11)
N8
VDDCORE
P
–
N9
GND
GPIO1
GPIO0
X15
P
I/O
I/O
O
Ground
–
N10
N11
N12
N13
General purpose IO
General purpose IO
X matrix drive line
X matrix drive line
Leave open
Leave open
Leave open
Leave open
X14
O
1. Either I2C-compatible or USB interface can be used, but only one interface should be used in any one design.
2. CHG is momentarily set (approximately 100 ms) as an input after power-up or reset for diagnostic purposes.
3. If using the self-powered USB configuration (rare), this pin must be connected to VBUS via potential divider of a suitable value for the supply level.
For example, with a 5V VBUS and 3.3V Vdd line, a 170 kΩ and 330 kΩ pair will typically be used.
4. It is recommend that RESET is connected to the host system.
5. Leave open for standard Atmel object protocol, or connect to GND to select the HID-I2C mode.
I
Input only
OD
P
Open drain output
Ground or power
O
Output only, push-pull
USB USB communications
10
mXT1664S1
9871EX–AT42–12/13
mXT1664S1
2.3
Schematics
2.3.1
I2C-compatible Mode – Digital Supply 2.7 – 3.3V
AVDD
VDD
C1
C2
2.2uF
100nF
GND
XVDD
GND
GND
VDD
VDD
VDD
L11
M13
M12
N13
N12
G3
X11
X12
X13
X14
X15
X16
X17
X18
X19
X20
X21
X22
X23
X24
X25
X26
X27
X28
X29
X30
X31
X11
X12
X13
X14
X15
X16
X17
X18
X19
X20
X21
X22
X23
X24
X25
X26
X27
X28
X29
X30
X31
GND
RESET
N4
Rc
Rp
Rp
RESET
G1
SDA
SCL
CHG
N5
M7
L9
H3
H2
H1
J2
SDA
SCL
CHG
J1
K3
K2
ADDSEL
H8
ADDSEL
G6
L1
L3
M1
M2
M3
N1
L10
COMMSEL
CHRG_IN
M11
GND
Notes
1. Capacitors C1 to C14 must be
X7R or X5R and placed <5 mm
N10
N11
GPIO1
GPIO0
C4
B4
A4
A5
C6
B6
A6
F6
Y51
Y50
Y49
Y48
Y47
Y46
Y45
Y44
Y43
Y42
Y41
Y40
Y39
Y38
Y37
Y36
Y35
Y34
Y33
Y32
Y31
Y30
Y29
Y28
Y27
Y26
Y25
Y24
Y23
Y22
Y21
Y20
Y19
Y18
Y17
Y16
Y15
Y14
Y13
Y12
Y11
mXT1664S1
Y51
Y50
Y49
Y48
Y47
Y46
Y45
Y44
Y43
Y42
Y41
Y40
Y39
Y38
Y37
Y36
Y35
Y34
Y33
Y32
Y31
Y30
Y29
Y28
Y27
Y26
Y25
Y24
Y23
Y22
Y21
Y20
Y19
Y18
Y17
Y16
Y15
Y14
Y13
Y12
Y11
N/C
L8
XIN
away from the pins for which they
act as bypass capacitors
N/C
M8
F7
XOUT
2. Pin L7 (VDD_INPUT) should be
connected to VDD.
C7
F1
F2
DBG_DATA
DBG_CLK
L6
L5
F3
3. Pin N2 (VDDUSB) should be
connected to VDD.
USBDM/DBG_DATA
USBDP/DBG_CLK
E1
E2
E3
D2
D3
B1
A1
C2
B2
A2
C3
B3
A3
A7
B7
F8
4. Pin N8 (VDDCORE) should
be decoupled to GND
VDD
through capacitors.
L7
VDD_INPUT
I2CMODE
5. Either I2C-compatible or USB
interface can be used, but only
one interface should be used in
any one design. Pin L10
I2CMODE
N6
H6
SYNC
A8
B8
C8
A9
C9
A10
C10
D11
D13
E11
E12
E13
(COMMSEL) should be
SYNC(TDI)
INDICATION H7
connected accordingly. (GND in
I2C-compatible mode or VDD in
USB mode).
INDICATION
N7
6. The device incorporates an
internal regulator that derives the
1.8V VDDCORE supply from
VDD. For stability of this
M10
regulator, a 10 µF input capacitor
(C7) and a 2.2 µF output
capacitor (C1) are required.
Capacitor C1 should have an
ESR of 0.5 Ω to 10 Ω.
GND
Reserved for
future use
7. Connect the I2CMODE pin to
GND to select the HID-I2C mode,
leave NC to select normal Object
based protocol mode.
11
9871EX–AT42–12/13
2.3.2
I2C-compatible Mode – Digital Supply 1.8V
AVDD
VDD
XVDD
GND
GND
VDD
VDD
VDD
L11
X11
X12
X13
X14
X15
X16
X17
X18
X19
X20
X21
X22
X23
X24
X25
X26
X27
X28
X29
X30
X31
X11
X12
X13
X14
X15
X16
X17
X18
X19
X20
X21
X22
X23
X24
X25
X26
X27
X28
X29
X30
X31
M13
M12
N13
N12
G3
G1
H3
H2
H1
J2
GND
RESET
N4
Rc
Rp
Rp
RESET
SDA
N5
M7
L9
SDA
SCL
CHG
SCL
CHG
J1
K3
K2
G6
L1
ADDSEL
H8
ADDSEL
L3
M1
M2
M3
N1
L10
COMMSEL
CHRG_IN
GND
M11
C4
B4
A4
A5
C6
B6
A6
F6
Y51
Y50
Y49
Y48
Y47
Y46
Y45
Y44
Y43
Y42
Y41
Y40
Y39
Y38
Y37
Y36
Y35
Y34
Y33
Y32
Y31
Y30
Y29
Y28
Y27
Y26
Y25
Y24
Y23
Y22
Y21
Y20
Y19
Y18
Y17
Y16
Y15
Y14
Y13
Y12
Y11
Y51
Y50
Y49
Y48
Y47
Y46
Y45
Y44
Y43
Y42
Y41
Y40
Y39
Y38
Y37
Y36
Y35
Y34
Y33
Y32
Y31
Y30
Y29
Y28
Y27
Y26
Y25
Y24
Y23
Y22
Y21
Y20
Y19
Y18
Y17
Y16
Y15
Y14
Y13
Y12
Y11
mXT1664S1
N/C
L8
XIN
N/C
M8
F7
XOUT
C7
F1
F2
DBG_DATA
DBG_CLK
L6
L5
F3
USBDM/DBG_DATA
USBDP/DBG_CLK
E1
E2
E3
D2
D3
B1
A1
C2
B2
A2
C3
B3
A3
A7
B7
F8
N10
N11
GPIO1
GPIO0
VDD
L7
Notes
VDD_INPUT
I2CMODE
1. Capacitors C1 to C13 must be
X7R or X5R and placed <5 mm
away from the pins for which
they act as bypass capacitors.
2. Pin L7 (VDD_INPUT) should
be connected to VDD.
3. Pin N2 (VDDUSB) should be
connected to VDD.
4. Pin N8 (VDDCORE) should be
connected to VDD.
I2CMODE
N6
H6
SYNC
A8
B8
C8
A9
C9
A10
C10
D11
D13
E11
E12
E13
SYNC
INDICATION H7
INDICATION
M10
N7
5. Pin L10 (COMMSEL) should
be connected to GND.
6. No internal regulators used so
C7 can be 1 µF.
GND
7. Connect the I2CMODE pin to
GND to select the HID-I2C
mode, leave NC to select
normal Object based protocol
mode.
Reserved for
future use
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mXT1664S1
2.3.3
USB Mode – Digital Supply 3.3V
AVDD
C1
C2
2.2uF
VDD
VDD_3V3
100nF
GND
XVDD
GND
GND
L11
X11
X12
X13
X14
X15
X16
X17
X18
X19
X20
X21
X22
X23
X24
X25
X26
X27
X28
X29
X30
X31
X11
X12
X13
X14
X15
X16
X17
X18
X19
X20
X21
X22
X23
X24
X25
X26
X27
X28
X29
X30
X31
M13
M12
N13
N12
G3
G1
H3
H2
H1
J2
GND
RESET
N4
RESET
VDD
N5
M7
L9
SDA
10K
SCL
J1
CHG
K3
K2
G6
L1
N/C
H8
ADDSEL
L3
VDD
See note 4
M1
M2
M3
N1
L10
COMMSEL
mXT1664S1
M11
CHRG_IN
XIN
C4
B4
A4
A5
C6
B6
A6
F6
Y51
Y50
Y49
Y48
Y47
Y46
Y45
Y44
Y43
Y42
Y41
Y40
Y39
Y38
Y37
Y36
Y35
Y34
Y33
Y32
Y31
Y30
Y29
Y28
Y27
Y26
Y25
Y24
Y23
Y22
Y21
Y20
Y19
Y18
Y17
Y16
Y15
Y14
Y13
Y12
Y11
Y51
Y50
Y49
Y48
Y47
Y46
Y45
Y44
Y43
Y42
Y41
Y40
Y39
Y38
Y37
Y36
Y35
Y34
Y33
Y32
Y31
Y30
Y29
Y28
Y27
Y26
Y25
Y24
Y23
Y22
Y21
Y20
Y19
Y18
Y17
Y16
Y15
Y14
Y13
Y12
Y11
C16
XT2
XIN L8
GND
16MHz
XOUT M8
F7
XOUT
C7
F1
C15
F2
USBDM
USBDP
L6
L5
F3
USBDM/DBG_DATA
USBDP/DBG_CLK
E1
E2
E3
D2
D3
B1
A1
C2
B2
A2
C3
B3
A3
A7
B7
F8
NOTES
1. Capacitors C1 to C16 must
N10
N11
GPIO1
GPIO0
be X7R or X5R and placed
<5 mm away from the pins
for which they act as bypass
capacitors.
VDD
L7
VDD_INPUT
INDICATION H7
INDICATION
I2CMODE
N/C
N6
H6
2. Pin L7 (VDD_INPUT) should
be connected to VDD.
3. Pin N8 (VDDCORE) should
be decoupled to GND via
capacitors.
4. Pin L10 (COMMSEL) should
be connected to VDD to
select the USB mode. If a
USB application is self-
powered (that is, one or
more touch controller power
rails not derived from
SYNC
A8
B8
C8
A9
C9
A10
C10
D11
D13
E11
E12
E13
SYNC(TDI)
M10
N7
V_USB), then COMMSEL
must be connected to a
divided down version of
V_USB, such that the
GND
Reserved for
future use
voltage on COMMSEL does
not exceed VDD.
5. Capacitors C15 and C16
should be 15 pF
13
9871EX–AT42–12/13
3. Touchscreen Basics
3.1
Sensor Construction
A touchscreen is usually constructed from a number of transparent electrodes. These are typically on
a glass or plastic substrate. They can also be made using non-transparent electrodes, such as
copper or carbon. Electrodes are normally formed by etching a material called Indium Tin Oxide
(ITO). This is a brittle ceramic material, of high optical clarity and varying sheet resistance. Thicker
ITO yields lower levels of resistance (perhaps tens to hundreds of Ω/square) at the expense of
reduced optical clarity. Lower levels of resistance are generally more compatible with capacitive
sensing. Thinner ITO leads to higher levels of resistance (perhaps hundreds to thousands of
Ω/square) with some of the best optical characteristics.
Interconnecting tracks formed in ITO can cause problems. The excessive RC time constants
formed between the resistance of the track and the capacitance of the electrode to ground can
inhibit the capacitive sensing function. In such cases, ITO tracks should be replaced by screen
printed conductive inks (non-transparent) outside the touchscreen’s viewing area.
A range of trade-offs also exist with regard to the number of layers used for construction. Atmel has
pioneered single-layer ITO capacitive touchscreens. For many applications these offer a near-
optimum cost/performance balance. With a single layer screen, the electrodes are all connected
using ITO out to the edges of the sensor. From there the connection is picked up with printed silver
tracks. Sometimes two overprinted silver tracking layers are used to reduce the margins between
the edge of the substrate and the active area of the sensor.
Two-layer designs can have a strong technical appeal where ultra-narrow edge margins are
required. They are also an advantage where the capacitive sensing function needs to have a very
precise cut-off as a touch is moved to just off the active sensor area. With a two-layer design the
QMatrix transmitter electrodes are normally placed nearest the bottom and the receiver electrodes
nearest the top. The separation between layers can range from hundreds of nanometers to
hundreds of microns, with the right electrode design and considerations of the sensing environment.
3.2
Electrode Configuration
The specific electrode designs used in Atmel touchscreens are the subject of various patents
and patent applications. Further information is available on request.
The device supports various configurations of electrodes as summarized below:
Touchscreens:
2 Touchscreens allowed
3X x 3Y minimum (depends on screen resolution)
32X x 52Y maximum (subject to other configurations)
1 Key Array allowed
Keys:
Up to 32 keys (subject to other configurations)
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3.3
Scanning Sequence
All channels are scanned in sequence by the device. There is a full parallelism in the scanning
sequence to improve overall response time. The channels are scanned by measuring capacitive
changes at the intersections formed between the first X line and all the Y lines. Then the
intersections between the next X line and all the Y lines are scanned, and so on, until all X and Y
combinations have been measured.
The device can be configured in various ways. It is possible to disable some channels so that they
are not scanned at all. This can be used to improve overall scanning time.
3.4
Touchscreen Sensitivity
3.4.1
Adjustment
Sensitivity of touchscreens can vary across the extents of the electrode pattern due to natural
differences in the parasitics of the interconnections, control chip, and so on. An important
factor in the uniformity of sensitivity is the electrode design itself. It is a natural consequence of
a touchscreen pattern that the edges form a discontinuity and hence tend to have a different
sensitivity. The electrodes at the far edges do not have a neighboring electrode on one side
and this affects the electric field distribution in that region.
A sensitivity adjustment is available for the whole touchscreen. This adjustment is a basic
algorithmic threshold that defines when a channel is considered to have enough signal change
to qualify as being in detect.
3.4.2
Mechanical Stackup
The mechanical stackup refers to the arrangement of material layers that exist above and
below a touchscreen. The arrangement of the touchscreen in relation to other parts of the
mechanical stackup has an effect on the overall sensitivity of the screen. QMatrix technology
has an excellent ability to operate in the presence of ground planes close to the sensor.
QMatrix sensitivity is attributed more to the interaction of the electric fields between the
transmitting (X) and receiving (Y) electrodes than to the surface area of these electrodes. For
this reason, stray capacitance on the X or Y electrodes does not strongly reduce sensitivity
Front panel dielectric material has a direct bearing on sensitivity. Plastic front panels are
usually suitable up to about 1.2 mm, and glass up to about 2.5 mm (dependent upon the
screen size and layout). The thicker the front panel, the lower the signal-to-noise ratio of the
measured capacitive changes and hence the lower the resolution of the touchscreen. In
general, glass front panels are near optimal because they conduct electric fields almost twice
as easily as plastic panels.
Note: Care should be taken using ultra-thin glass panels as retransmission effects can
occur.
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4. Detailed Operation
4.1
Power-up/Reset
There is an internal Power-on Reset (POR) in the device.
The device must be held in RESET (active low) while the power supplies (Vdd and AVdd) are
powering up. If a slope or slew is applied to the digital or analog supplies (Vdd, AVdd and
XVdd) must reach their nominal values before the RESET signal is de-asserted (that is, goes
high). This is shown in Figure 4-1. See Section 9.2 on page 58 for nominal values for Vdd,
AVdd and XVdd. Please note that the XVdd rail has a maximum rate of rise specification
(see Section 9.3.3 on page 59), that is, a soft-start XVdd supply must be used.
Figure 4-1. Power Sequencing on the mXT1664S1
AVdd
XVdd
> 0 ns
Vdd
(Vdd)
RESET
> 90 ns
Note:
1) Vdd and AVdd can be powered up in any order
2) XVdd must not be powered up until after Vdd and
must obey the rate-of-rise specification
The digital or analog (AVdd) supplies can be applied independently and in any order on the
mXT1664S1 during power-up. Vdd must be applied to the device before XVdd to ensure that
the different power domains in the device are initialized correctly. Typically this can be done by
connecting the enable pin of the Switched Mode Power Supply (SMPS) supplying XVdd to a
10 kΩ pull-up resistor connected to the Vdd, but the XVdd can be controlled separately by the
host, if required.
After power-up, the device takes 65 ms before it is ready to start communications. Vdd must
drop to below 1.45 V in order to effect a proper POR. See Section 9 on page 58 for further
specifications.
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mXT1664S1
If the RESET line is released before the AVDD and /or XVDD supplies have reached their
nominal voltage (see Figure 4-2), then some additional operations need to be carried out by
the host. There are two options open to the host controller:
• Start the part in deep sleep mode and then send the command sequence to set the cycle
time to wake the part and allow it to run normally. Note that in this case a calibration
command is also needed.
• Send a reset command.
Figure 4-2. Power Sequencing on the mXT1664S1 – Late rise on AVDD
RESET disasserted before AVdd/X
at nominal level
(Nom)
Avdd or
XVdd
(Nom)
Vdd
(Vdd)
RESET
The RESET pin can be used to reset the device whenever necessary. The RESET pin must
be asserted low for at least 90 ns to cause a reset. After releasing the RESET pin the device
takes ~65 ms before it is ready to start communications. It is recommended to connect the
RESET pin to a host controller to allow it to initiate a full hardware reset without requiring a
power-down.
Note that the voltage level on the RESET pin of the device must never exceed Vdd (digital
supply voltage).
A software reset command can be used to reset the chip (refer to the Command Processor
object in the mXT1664S 2v0 Protocol Guide). A software reset takes a maximum of
280 ms. After the chip has finished it asserts the CHG line to signal to the host that a message
is available. The reset flag is set in the Message Processor object to indicate to the host that it
has just completed a reset cycle. This bit can be used by the host to detect any unexpected
brownout events. This allows the host to take any necessary corrective actions, such as
reconfiguration.
A checksum check is performed on the configuration settings held in the nonvolatile memory.
If the checksum does not match a stored copy of the last checksum, then this indicates that
the settings have become corrupted. This is signaled to the host by setting the configuration
error bit in the message data for the Command Processor object (refer to the mXT1664S 2v0
Protocol Guide for more information).
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9871EX–AT42–12/13
Note that the CHG line is momentarily set (approximately 100 ms) as an input after power-up
or reset for diagnostic purposes. It is therefore particularly important that the line should be
allowed to float high via the CHG line pull-up resistor during this period. It should not be driven
by the host.
At power-on, the device performs a self-test routine to check for shorts which might cause
damage to the device. Refer to the Self Test T25 section of the mXT1664S 2v0 Protocol Guide
for more details about this process.
4.2
Calibration
Calibration is the process by which a sensor chip assesses the background capacitance on
each channel. Channels are only calibrated on power-up and when:
• The channel is enabled (that is, activated).
OR
• The channel is already enabled and one of the following applies:
– The channel is held in detect for longer than the Touch Automatic Calibration
setting (refer to the mXT1664S 2v0 Protocol Guide for more information on
TCHAUTOCAL setting in the Acquisition Configuration object).
– The signal delta on a channel is at least the touch threshold (TCHTHR) in the
anti-touch direction, while no other touches are present on the channel matrix
(refer to the mXT1664S 2v0 Protocol Guide for more information on the TCHTHR
field in the Multiple Touch Touchscreen and Key Array objects).
– The host issues a recalibrate command.
– Certain configuration settings are changed.
A status message is generated on the start and completion of a calibration.
Note that the device performs a global calibration; that is, all the channels are calibrated
together.
4.3
Operational Modes
The device operates in two modes: active (touch detected) and idle (no touches detected).
Both modes operate as a series of burst cycles. Each cycle consists of a short burst (during
which measurements are taken) followed by an inactive sleep period. The difference between
these modes is the length of the cycles. Those in idle mode typically have longer sleep
periods. The cycle length is configured using the IDLEACQINT and ACTVACQINT settings in
the Power Configuration object. In addition, an Active to Idle timeout (ACTV2IDLETO) setting
is provided.
Refer to the mXT1664S 2v0 Protocol Guide for full information on how these modes operate,
and how to use the settings provided.
4.4
Touchscreen Layout
The physical matrix can be configured to have one or more touch objects. These are
configured using the appropriate touch objects (Multiple Touch Touchscreen and Key
Array Key Array). It is not mandatory to have all the allowable touch objects present. The
objects are disabled by default so only those that you wish to use need to be enabled. Refer to
the mXT1664S 2v0 Protocol Guide for more information on configuring the touch objects.
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mXT1664S1
When designing the physical layout of the touch panel, obey the following rules:
– Each touch object should be a regular rectangular shape in terms of the lines it
uses.
– Touch objects can share X and Y lines, as necessary. Note, however, that the first
instance (instance 0) of the Multiple Touch Touchscreen T9 object cannot share Y
lines if the SlimSensor T56 object is enabled.
– The design of the touch objects does not physically need to be on a strict XY grid
pattern.
4.5
Signal Processing
4.5.1
Adjacent Key Suppression Technology
Adjacent Key Suppression (AKS) technology is a patented method used to detect which touch
object is touched when objects are located close together. A touch in a group of AKS objects
is only indicated on the object in that group that is touched first. This is assumed to be the
intended object. Once an object in an AKS group is in detect, there can be no further
detections within that group until the object is released. Objects can be in more than one AKS
group.
Note that AKS technology works best when it operates in conjunction with a detect integration
setting of several acquisition cycles.
The device has two levels of AKS. The first level works between the touch objects (Multiple
Touch Touchscreen T9 and Key Array T15). The touch objects are assigned to AKS groups. If
a touch occurs within one of the touch objects in a group, then touches within other objects
inside that group are suppressed. For example, if a Touchscreen and a Key Array are placed
in the same AKS group, then a touch in the Touchscreen will suppress touches in the Key
Array, and vice versa.
The second level of AKS is internal AKS within an individual Key Array object (note that
internal AKS is not present on other types of touch objects, only a Key Array). If internal AKS is
enabled, then when one key is touched, touches on all the other keys within the Key Array are
suppressed.
AKS is configured using the touch objects (Multiple Touch Touchscreen T9 or Key Array T15).
Refer to the mXT1664S 2v0 Protocol Guide for more information.
Note: If a touch is in detect and then AKS is enabled, that touch will not be forced out of
detect. It will not go out of detect until the touch is released. AKS will then operate
normally. This applies to both levels of AKS.
4.5.2
Detection Integrator
The device features a touch detection integration mechanism. This acts to confirm a detection
in a robust fashion. A counter is incremented each time a touch has exceeded its threshold
and has remained above the threshold for the current acquisition. When this counter reaches
a preset limit the sensor is finally declared to be touched. If, on any acquisition, the signal is
not seen to exceed the threshold level, the counter is cleared and the process has to start from
the beginning.
The detection integrator is configured using the appropriate touch objects (Multiple Touch
Touchscreen T9, Key Array T15). Refer to the mXT1664S 2v0 Protocol Guide for more
information.
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9871EX–AT42–12/13
4.5.3
Digital Filtering and Noise Suppression
The mXT1664S1 supports the on-chip filtering of the acquisition data received from the
sensor. Specifically, the maXCharger T62 object provides an algorithm to suppress the effects
of noise (for example, from a noisy charger plugged into the user’s product). This algorithm
can automatically adjust some of the acquisition parameters on-the-fly to filter the analog-to-
digital conversions (ADCs) received from the sensor. The algorithm can make use of a Grass
Cutter (which rejects any samples outside a predetermined limit).
Noise suppression is triggered when a noise source is detected (typically when a charger is
turned on). A hardware trigger can be implemented using the CHRG_IN pin. Alternatively, the
host’s driver code can indicate when a noise source is present.
An alternative burst mode on the X lines, known as Dual X Drive, is provided. This improves
the signal-to-noise ratio (SNR) on a closely spaced X sensor matrix (when finger touches are
likely to cover more than one X line).
Refer to the mXT1664S 2v0 Protocol Guide for more information on the maXCharger T62
object.
4.5.4
4.5.5
GPIO Pins
The mXT1664S1 has two GPIO pins. The pins can be set to be either an input or an output, as
required. The GPIO pins are configured using the GPIO/PWM Configuration T19 object.
Grip Suppression
The device has a grip suppression mechanism to suppress false detections when the user
grips a handheld device.
Grip suppression works by specifying a boundary around a touchscreen, within which touches
can be suppressed whilst still allowing touches in the center of the touchscreen. This ensures
that a “rolling” hand touch (such as when a user grips a mobile device) is suppressed. A “real”
(finger) touch towards the center of the screen is allowed.
Grip suppression is configured using the Grip Suppression T40 object. There is one instance
of the Grip Suppression T40 object for each Multiple Touch Touchscreen T9 object present on
the device. Refer to the mXT1664S 2v0 Protocol Guide for more information.
4.5.6
Baseline Reference
The device supports using a set of known-good baseline references to eliminate problems
associated with calibrating in the presence of touches, moisture or foreign objects.
The maXStartup T66 object enables baseline references to be generated and stored in a
controlled environment on the production line. These values can then be restored on
calibration instead of relying on current state of the screen which may be in contact with a
touch, moisture or foreign objects such as keys or coins. Supporting algorithms are used to
compensate the references for variations in different environments. Refer to the mXT1664S
2v0 Protocol Guide for more information.
4.5.7
Lens Bending
The device supports algorithms to eliminate disturbances from the measured signal and also
to measure the bend component.
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mXT1664S1
When the sensor suffers from the screen deformation (lens bending) the signal values
acquired by normal procedure are corrupted by the disturbance component (bend). The
amount of bend depends on:
• the mechanical and electrical characteristics of the sensor
• the amount and location of the force applied by the user touch to the sensor
The Lens Bending T65 object measures the bend component and compensates for any distortion
caused by the bend. As the bend component is primarily influenced by the user touch force, it
can be used as a secondary source to identify the presence of a touch. The additional benefit
of the Lens Bending T65 object is that it will eliminate LCD noise as well. Refer to the mXT1664S
2v0 Protocol Guide for more information.
4.5.8
Shieldless Support
The device can support shieldless sensor design even with a noisy LCD. The SlimSensor T56
object provides a number of algorithms to suppress the effect of noise emitted by the display.
The SlimSensor T56 display noise suppression operates on a completely different mechanism
to the maXCharger T62 object. This allows the device to overcome display noise
simultaneously with charger noise.
The device can make use of the following mechanisms to overcome display noise:
• Optimal Integration is not filtering as such, instead it is a feature that enables the user to
use a shorter integration window. The integration window optimizes the amount of charge
collected against the amount of noise collected, to ensure an optimal SNR. This feature
also benefits the system in the presence of an external noise source such as charger.
Refer to the mXT1664S 2v0 Protocol Guide for more information on the SlimSensor T56
object.
4.5.9
Stylus Support
The mXT1664S1 allows for the particular characteristics of stylus touches, whilst still allowing
conventional finger touches to be detected. Stylus touches are configured by the Stylus T47
object. There is one instance of the Stylus T47 object for each Multiple Touch Touchscreen T9
object present on the device.
The device supports the active stylus through the Active Stylus T63 object.
For example, stylus support ensures that the small touch area of a stylus registers as a touch,
as this would otherwise by considered too small for the touchscreen. Additionally, there are
controls to distinguish a stylus touch from an unwanted approaching finger (such as on the
hand holding the stylus).
The touch sensitivity and threshold controls for stylus touches are configured separately from
those for conventional finger touches so that both types of touches can be accommodated.
4.5.10
Unintentional Touch Suppression
The Touch Suppression T42 object provides a mechanism to suppress false detections from
unintentional touches from a large body area, such as from a face, ear or palm. The Touch
Suppression T42 object also provides Maximum Touch Suppression to suppress all touches if
more than a specified number of touches has been detected. There is one instance of the
Touch Suppression T42 object for each Multiple Touch Touchscreen T9 object present on the
device. Refer to the mXT1664S 2v0 Protocol Guide for more information.
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9871EX–AT42–12/13
4.5.11
Zone Indication
The mXT1664S1 allows the host to define a Zone on the touchscreen and touches detected in
the defined zone. The zone can be configured using the Zone Indication T73 object. Note that
only finger touches can be detected in the defined zone, refer to the mXT1664S 2v0 Protocol
Guide for more information on the Zone Indication T73 object.
4.6
Circuit Components
4.6.1
XVdd Power Supply
The X line driver power supply XVdd can be used in two different modes:
• XVdd connected to AVdd. This mode limits the range of XVdd to 2.7 – 3.3V.
• XVdd connected to an external supply. In this configuration the external supply should be in
the range 2.7 – 10.0V. The higher voltages improve the SNR of the system.
• If XVdd < 4.75 V, please note restriction on minimum Cx in Section 9.2 on page 58.
4.6.2
Bypass Capacitors
Each power supply (Vdd, XVdd and AVdd) requires a 1 µF bypass capacitor. If the internal
1.8V VDDCORE regulator is used, the Vdd 1 µF should be replaced with a 10 µF capacitor
and a 2.2 µF capacitor should be added on the VDDCORE pin. In addition, there should be a
100 nF bypass capacitor on each power trace. The capacitors should be ceramic X7R or X5R.
See the schematics in Section 2.3 on page 11 for more details.
The PCB traces connecting the bypass capacitors to the pins of the device must not exceed
5 mm in length. This limits any stray inductance that would reduce filtering effectiveness. See
also Section 9.11 on page 68.
4.6.3
4.6.4
Supply Quality
While the device has good Power Supply Rejection Ratio properties, poorly regulated and/or
noisy power can significantly reduce performance. See Section 9.11 on page 68.
Always operate the device with a well-regulated and clean AVdd (and XVdd, if used) supply. It
supplies the sensitive analog stages in the device. See Figure 9-1 on page 74 for an example
XVdd supply.
Supply Sequencing
Vdd and AVdd can be powered independently of each other without damage to the device.
Vdd must be applied to the device before XVdd to ensure proper initialization of the device. All
voltage ranges should be used with in the limits specified in Section 9.2 on page 58.
Make sure that any lines connected to the device are below or equal to Vdd during power-up.
For example, if RESET is supplied from a different power domain to the VDD pin, make sure
that it is held low when Vdd is off. If this is not done, the RESET signal could parasitically
couple power via the RESET pin into the Vdd supply.
4.6.5
Oscillator
A 16 MHz crystal oscillator must be connected to the device when the device is operating in
USB mode. A crystal oscillator with a minimum accuracy of 100 ppm must be used.
An external oscillator is not needed in I2C-compatible mode.
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mXT1664S1
4.6.6
Decoupling Requirements
Certain pins have specific decoupling requirements:
• Pin L7 (VDD_INPUT) should be connected to VDD.
• Pin N8 (VDDCORE) is a decoupling connection for an internal LDO (Low Drop-Out
regulator) circuit and should not be powered by an external supply unless in 1.8 V I2C-
compatible mode.
See also the schematics in Section 2.3 on page 11.
4.6.7
PCB Cleanliness
Modern no-clean-flux is generally compatible with capacitive sensing circuits.
CAUTION: If a PCB is reworked to correct soldering faults relating to any of
the device devices, or to any associated traces or components, be sure that you
fully understand the nature of the flux used during the rework process. Leakage
currents from hygroscopic ionic residues can stop capacitive sensors from
functioning. If you have any doubts, a thorough cleaning after rework may be the
only safe option.
4.7
4.8
PCB Layout
Debugging
See Appendix A on page 72 for general advice on PCB layout.
The device provides a mechanism for obtaining raw data for development and testing
purposes by reading data from the Diagnostic Debug T37 object. Refer to the mXT1664S 2v0
Protocol Guide for more information on this object.
A second mechanism is provided that allows the host to read the real-time raw data using the
low-level debug port. This can be accessed via the SPI interface or the USB interface. Note
that if both the I2C-compatible and USB interfaces are used for normal communications, the
debug data is output on the USB interface. Refer to QTAN0050, Using the maXTouch Debug
Port, for more information on the debug port.
There is also a Self Test T25 object that runs self-test routines in the device to find hardware
faults on the sense lines and the electrodes. This object also performs an initial pin fault test
on power-up to ensure that there is no X-to-Y short before the high-voltage supply is enabled
inside the chip. A high-voltage short into the analog circuitry would break the device.
Refer to the mXT1664S 2v0 Protocol Guide and QTAN0059, Using the maXTouch Self Test
Feature, for more information on the Self Test T25 object.
4.9
Communications
Communication with the host is achieved using either the I2C-compatible interface (see
Section 5 on page 25), the HID-I2C-compatible interface (see Section 7 on page 45), or the
USB interface (see Section 6 on page 32). Any interface can be used, depending on the
needs of the user’s project, but only one interface should be used in any one design. The
selection of the I2C-compatible or the HID-I2C-compatible interface is determined by the
I2CMODE pin.
The interface is selected using the COMMSEL pin. Connect COMMSEL to Vdd to select the
USB interface, or to GND to select one of the two I2C-compatible interfaces.
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9871EX–AT42–12/13
Note that you only need to connect those pins that are actually required for use with the
chosen communications interface. This ensures optimal power consumption and correct
functioning. See Section 2.2 on page 6 for details on what should be done with the
unconnected pins.
4.10 Configuring the Device
The device has an object-based protocol that organizes the features of the device into objects
that can be controlled individually. This is configured using the Object Protocol common to
many of Atmel’s touch sensor devices. For more information on the Object Protocol and its
implementation on the device, refer to the mXT1664S 2v0 Protocol Guide.
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9871EX–AT42–12/13
mXT1664S1
5. I2C-compatible Communications
5.1
Communications Protocol
The device can use an I2C-compatible interface for communication. See Appendix E on
page 84 for details of the I2C-compatible protocol.
The I2C-compatible interface is used in conjunction with the CHG line. The CHG line going
active signifies that a new data packet is available. This provides an interrupt-style interface
and allows the device to present data packets when internal changes have occurred.
5.2
I2C-compatible Addresses
5.2.1
I2C-compatible Addresses
The device supports two I2C-compatible device addresses that are selected using the
ADDSEL line at start-up. The two internal I2C-compatible device addresses are 0x4A
(ADDSEL low) and 0x4B (ADDSEL floating or high). These are shifted left to form the SLA+W
or SLA+R address when transmitted over the I2C-compatible interface, as shown in
Figure 5-1.
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Read/wri
te
Address: 0x4A or 0x4B
5.3
Writing To the Device
A WRITE cycle to the device consists of a START condition followed by the I2C-compatible
address of the device (SLA+W). The next two bytes are the address of the location into which
the writing starts. The first byte is the Least Significant Byte (LSByte) of the address, and the
second byte is the Most Significant Byte (MSByte). This address is then stored as the address
pointer.
Subsequent bytes in a multi-byte transfer form the actual data. These are written to the
location of the address pointer, location of the address pointer +1, location of the address
pointer + 2, and so on. The address pointer returns to its starting value when the WRITE
cycle’s STOP condition is detected.
Figure 5-1 shows an example of writing four bytes of data to contiguous addresses starting at
0x1234.
Figure 5-1. Example of a Four-byte Write Starting at Address 0x1234
START SLA+W
0x34
0x12
0x96
0x9B
0xA0
0xA5
STOP
Write Address
(LSB, MSB)
Write Data
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9871EX–AT42–12/13
5.4
I2C-compatible Writes in Checksum Mode
In I2C-compatible checksum mode an 8-bit CRC is added to all I2C-compatible writes. The
CRC is sent at the end of the data write as the last byte before the STOP condition. All the
bytes sent are included in the CRC, including the two address bytes. Any command or data
sent to the device is processed even if the CRC fails.
To indicate that a checksum is to be sent in the write, the most significant bit of the MSByte of
the address is set to 1. For example, the I2C-compatible command shown in Figure 5-2 writes
a value of 150 (0x96) to address 0x1234 with a checksum. The address is changed to 0x9234
to indicate checksum mode.
Figure 5-2. Example of a Write To Address 0x1234 With a Checksum
Checksum
START SLA+W
0x34
0x92
0x96
STOP
Write Address
(LSB, MSB)
Write Data
5.5
Reading From the Device
Two I2C-compatible bus activities must take place to read from the device. The first activity is
an I2C-compatible write to set the address pointer (LSByte then MSByte). The second activity
is the actual I2C-compatible read to receive the data. The address pointer returns to its starting
value when the read cycle’s NACK is detected.
It is not necessary to set the address pointer before every read. The address pointer is
updated automatically after every read operation. The address pointer will be correct if the
reads occur in order. In particular, when reading multiple messages from the Message
Processor T5 object, the address pointer is automatically reset to allow continuous reads (see
Section 5.6).
The WRITE and READ cycles consist of a START condition followed by the I2C-compatible
address of the device (SLA+W or SLA+R respectively).
Figure 6-10 shows the I2C-compatible commands to read four bytes starting at address
0x1234.
Figure 5-3. Example of a Four-byte Read Starting at Address 0x1234
Set Address Pointer
START SLA+W
0x34
0x12
STOP
Read Address
(LSB, MSB)
Read Data
START SLA+R
0x96
0x9B
0xA0
0xA5
STOP
Read Data
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mXT1664S1
5.6
Reading Status Messages with DMA
The device facilitates the easy reading of multiple messages using a single continuous read
operation. This allows the host hardware to use a direct memory access (DMA) controller for
the fast reading of messages, as follows:
1. The host uses a write operation to set the address pointer to the start of the Message
Count T44 object, if necessary. (1) If a checksum is required on each message, the
most significant bit of the MSByte of the read address must be set to 1.
2. The host starts the read operation of the message by sending a START condition.
3. The host reads the Message Count T44 object (one byte) to retrieve a count of the
pending messages (refer to the mXT1664S 2v0 Protocol Guide for details).
4. The host calculates the number of bytes to read by multiplying the message count by
the size of the Message Processor T5 object. (2)
Note that the size of the Message Processor T5 object as recorded in the Object
Table includes a checksum byte. If a checksum has not been requested, one byte
should be deducted from the size of the object. That is: number of bytes = count x
(size-1).
5. The host reads the calculated number of message bytes. It is important that the host
does not send a STOP condition during the message reads, as this will terminate the
continuous read operation and reset the address pointer. No START and STOP
conditions must be sent between the messages.
6. The host sends a STOP condition at the end of the read operation after the last
message has been read. The NACK condition immediately before the STOP
condition resets the address pointer to the start of Message Count T44 object.
Figure 5-4 on page 28 shows an example of using a continuous read operation to read three
messages from the device without a checksum. Figure 5-5 on page 29 shows the same
example with a checksum.
1. The STOP condition at the end of the read resets the address pointer to its initial location, so it may already be
pointing at the Message Count T44 object following a previous message read.
2. The host should have already read the size of the Message Processor T5 object in its initialization code.
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9871EX–AT42–12/13
Figure 5-4. Continuous Message Read Example – No Checksum
Set Address Pointer
START SLA+W
LSB
MSB
STOP
Start Address of
Message Count Object
Read Message Count
Continuous
Read
START SLA+R Count = 3
Message Count Object
Read Message Data
(size – 1) bytes
Report ID
Data
Data
Message Processor Object – Message # 1
Report ID
Data
Data
Message Processor Object – Message # 2
Report ID
Data
Data
STOP
Message Processor Object – Message # 3
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mXT1664S1
Figure 5-5. Continuous Message Read Example – I2C-compatible Checksum Mode
Set Address Pointer
MSB |
0x80
Checksum
START SLA+W
LSB
STOP
Start Address of
Message Count Object
Read Message Count
START SLA+R Count = 3
Continuous
Read
Message Count Object
Read Message Data
size bytes
Report ID
Checksum
Data
Data
Message Processor Object – Message # 1
Report ID
Checksum
Data
Data
Message Processor Object – Message # 2
Report ID
Checksum
Data
Data
STOP
Message Processor Object – Message # 3
There are no checksums added on any other I2C-compatible reads. An 8-bit CRC can be
added, however, to all I2C-compatible writes, as described in Section 5.4 on page 26.
An alternative method of reading messages using the CHG line is given in Section 5.7.
5.7
CHG Line
The CHG line is an active-low, open-drain output that is used to alert the host that a new
message is available in the Message Processor T5 object. This provides the host with an
interrupt-style interface with the potential for fast response times. It reduces the need for
wasteful I2C-compatible communications.
The CHG line remains low as long as there are messages to be read. The host should be
configured so that the CHG line is connected to an interrupt line that is level-triggered. The
host should not use an edge-triggered interrupt as this means adding extra software
precautions.
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9871EX–AT42–12/13
The CHG line should be allowed to float during normal usage. This is particularly important
after power-up or reset (see Section 4.1 on page 16).
A pull-up resistor is required, typically 10 kΩ to Vdd.
The CHG line operates in two modes, as defined by the Communications Configuration T18
object (refer to the mXT1664S 2v0 Protocol Guide).
Mode 0
NA
CK
ACK
I2C-compatible Interface
.
.
.
.
.
.
.
.
.
.
.
.
STA
RT
SLA-
R
B
0
B
1
B
n
B
0
B
1
B
n
B
0
B
1
B
n
STO
P
Message
Message #1
Message #2
#m
CHG Line
.
.
.
CHG line high or low; see text
Mode 1
I2C-compatible Interface
ACK
.
.
.
.
.
.
.
.
.
.
.
.
STA
RT
SLA-
R
B
0
B
1
B
n
B
0
B
1
B
n
B
0
B
1
B
n
STO
P
Message
Message #1
Message #2
#m
CHG Line
.
.
.
CHG line high or low; see text
In Mode 0:
1. The CHG line goes low to indicate that a message is present.
2. The CHG line goes high when the first byte of the first message (that is, its report ID)
has been sent and acknowledged (ACK sent) and the next byte has been prepared in
the buffer.
3. The STOP condition at the end of an I2C-compatible transfer causes the CHG line to
stay high if there are no more messages. Otherwise the CHG line goes low to
indicate a further message.
Mode 0 allows the host to continually read messages. Messaging reading ends when a report
ID of 255 (“invalid message”) is received. Alternatively the host ends the transfer by sending a
NACK after receiving the last byte of a message, followed by a STOP condition. If and when
there is another message present, the CHG line goes low, as in step 1. In this mode the state
of the CHG line does not need to be checked during the I2C-compatible read.
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mXT1664S1
In Mode 1:
1. The CHG line goes low to indicate that a message is present.
2. The CHG line remains low while there are further messages to be sent after the
current message.
3. The CHG line goes high again only once the first byte of the last message (that is, its
report ID) has been sent and acknowledged (ACK sent) and the next byte has been
prepared in the output buffer.
Mode 1 allows the host to continually read the messages until the CHG line goes high, and the
state of the CHG line determines whether or not the host should continue receiving messages
from the device.
Note: The state of the CHG line should be checked only between messages and not
between the bytes of a message. The precise point at which the CHG line changes
state cannot be predicted and so the state of the CHG line cannot be guaranteed
between bytes.
The Communications Configuration T18 object can be used to configure the behavior of the
CHG line. In addition to the CHG line operation modes described above, this object allows the
use of edge-based interrupts, as well as direct control over the state of the CHG line. Refer to
the mXT1664S 2v0 Protocol Guide for more information.
5.8
5.9
SDA, SCL
The I2C-compatible bus transmits data and clock with SDA and SCL, respectively. These are
open-drain. The device can only drive these lines low or leave them open. The termination
resistors (Rp) pull the line up to Vdd if no I2C-compatible device is pulling it down.
The termination resistors should be chosen so that the rise times on SDA and SCL meet the
I2C-compatible specifications for the interface speed being used, bearing in mind other loads
on the bus, (see Section 9.7 on page 67).
Clock Stretching
The device supports clock stretching in accordance with the I2C specification. It may also
instigate a clock stretch if a communications event happens during a period when the device is
busy internally. The maximum clock stretch is approximately 10 – 15 ms.
The device has an internal bus monitor that can reset the internal I2C-compatible hardware if
SDA or SCL is stuck low for more than 200 ms. This means that if a prolonged clock stretch of
more than 200 ms is seen by the device, then any ongoing transfers with the device may be
corrupted. The bus monitor is enabled or disabled using the Communications Configuration
T18 object. Refer to the mXT1664S 2v0 Protocol Guide for more information.
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9871EX–AT42–12/13
6. USB Communications
6.1
Communications Protocol
The device is a composite USB device with two Human Interface Device (HID) interfaces:
• Interface 0 – This interface provides a Digitizer HID that supplies touch information to the
Host for passing on to a PC’s operating system. This interface is supported by Microsoft®
Windows® 8 without the need for additional software. The HID identifier string is
“Atmel maXTouch Digitizer”.
• Interface 1 – This interface provides a Generic HID that allows the host to communicate
with the device using the Object Protocol. The HID identifier string is
“Atmel maXTouch Control”.
The topography of the USB device is shown in Figure 6-1.
Figure 6-1. USB Topography
Endpoint 0
(Control)
Composite Device
Interface 0
“Atmel maXTouch Digitizer”
(Digitizer HID)
Interface 1
“Atmel maXTouch Control”
(Generic HID)
Endpoint 3
Endpoint 1
(In)
Endpoint 2
(Out)
(In)
Communication takes place using Full-speed USB at 12 Mbps.
For more information on the USB HID specifications visit www.usb.org.
6.2
Endpoint Addresses
The endpoint addresses are listed in Table 6-1.
Table 6-1.
Endpoint
Endpoint 0
Endpoint 1
Endpoint 2
Endpoint 3
Endpoint Addresses
Direction
Address
–
Bidirectional (control)
In
0x81
0x02
0x83
Out
In
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mXT1664S1
6.3
Composite Device
The composite device is a USB 2.0-compliant USB composite device running at full speed
(12 Mbps). It has the following specification:
Vendor ID:
Product ID:
Version:
0x03EB (Atmel)
0x212C (mXT1664S1)
16-bit Version & Build Identifier in the form 0xVVBB, where:
VV = Version Major (Upper 4 bits) / Minor (Lower 4 bits)
BB = Build number in BCD format
The composite device has one bidirectional endpoint: the Control Endpoint (Endpoint 0). It is
used by the USB Host to interrogate the USB device for details on its configurations,
interfaces and report structures. It is also used to apply general device settings relating to USB
Implementation.
6.4
Interface 0 (Digitizer HID)
6.4.1
Normal Touch Report
Interface 0 is a Digitizer-class HID, compliant with HID specification 1.11 with amendments. (1)
This interface consists of a single interrupt-In endpoint (Endpoint 3).
The format of an input report is shown in Figure 6-3. Each input report start with a USB Report
ID (2) (value 0x01). This is followed by 6 sets of data (11 bytes each) that describe the status of
up to 5 active touches. The input report is terminated by a single byte that contains the number
of active touches.
Figure 6-2. Input Report Packet
Touch 1
(11bytes)
Touch 2
(11bytes)
Touch 3
(11bytes)
Touch 4
(11bytes)
Touch 5
(11bytes)
Scan
Time
Count
0x01
USB
Active Touch Status Data
Report ID
Any unused touch data bytes are set to zero (for example, the data for one active touch would
be followed by 56 zeroed bytes). If there are more than five active touches to be reported, a
further input report is sent with the remaining touch data. In this case, the count (for all
touches) is sent in the last count byte and the count byte in the first report is zero. An example
of the input report packets for 7 active touches is shown in Figure 6-3 on page 34.
1. This is an implementation of Microsoft’s USB HID specification for Multitouch digitizers.
2. The term USB Report ID should not be confused with the term Report Id as used in the Object Protocol; the two are
entirely different concepts.
33
9871EX–AT42–12/13
Figure 6-3. Example Input Report Packets for 7 Active Touches
Touch 1
(11bytes)
Touch 2
(11bytes)
Touch 3
(11bytes)
Touch 4
(11bytes)
Touch 5
(11bytes)
Scan
Time
Count=7
0
0x01
0x01
Touch 6
(11bytes)
Touch 7
(11bytes)
0
0
0
Scan
Time
(11bytes)
(11bytes)
(11bytes)
USB
Active Touch Status Data
Report ID
The input report format depends on the geometry calculation field (TCHGEOMEN) of the
Digitizer HID Configuration T43 object. Table 6-3 and Table 6-3 gives the detailed format of an
input report packet..
Table 6-2.
Input Report Format when TCHGEOMEN is Enabled
Byte
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
USB Report ID
1
Touch ID (first touch)
Reserved
Status
2
X Position LSByte (first touch)
X Position MSBits (first touch)
X Position LSByte (first touch)
3
0
0
0
0
0
0
0
0
0
0
0
0
0
4
5
0
X Position MSBits (first touch)
6
7
Y Position LSByte (first touch)
0
Y Position MSBits (first touch)
8
Y Position LSByte (first touch)
9
0
Y Position MSBits (first touch)
10
Touch width
Touch height
11
12 – 22
23 – 33
34 – 44
45 – 55
56 – 57
58
Touch data for second touch – same format as bytes 1 – 11
Touch data for third touch – same format as bytes 1 – 11
Touch data for fourth touch – same format as bytes 1 – 11
Touch data for fifth touch – same format as bytes 1 – 11
Scan time
Contact count
Table 6-3.
Input Report Format when TCHGEOMEN is Disabled
Byte
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
1
USB Report ID
Touch ID (first touch)
Reserved
Status
2
X Position LSByte (first touch)
X Position MSBits (first touch)
3
0
0
0
0
4 – 5
Reserved
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9871EX–AT42–12/13
mXT1664S1
Table 6-3.
Byte
Input Report Format when TCHGEOMEN is Disabled
Bit 7
Bit 6
Bit 5
Bit 4
Y Position LSByte (first touch)
Y Position MSBits (first touch)
Bit 3
Bit 2
Bit 1
Bit 0
6
7
0
0
0
0
8 – 9
Reserved
Reserved
10 –11
12 – 22
23 – 33
34 – 44
45 – 55
56 – 57
58
Touch data for second touch – same format as bytes 1 – 11
Touch data for third touch – same format as bytes 1 – 11
Touch data for fourth touch – same format as bytes 1 – 11
Touch data for fifth touch – same format as bytes 1 – 11
Scan time
Contact count
In Table 6-3:
• Byte 1:
Status: 1 = In detect, 0 = Not in detect.
Touch ID: Identifies the touch for which this is a status report (starting from 1).
• Bytes 2 to 9:
X and Y positions: These are scaled to 12-bit resolution. This means that the
upper four bits of the MSByte will always be zero.
Bytes 4, 5, 8, 9, 10 and 11 are Reserved when TCHGEOMEN field is set to 0.
• Byte 10:
Touch Width: Reports the width of the detected touch.
• Byte 11:
Touch Height: Reports the height of the detected touch.
• Byte 56 to 57:
Scan Time: Timestamp associated with the current report frame with a 10 kHz
resolution.
Note that the scan time for each report packet of a single frame is same.
• Byte 58:
Contact Count: Non-zero value in the first report packet of a frame indicating the
total number of report packets in the frame. Zeros in the subsequent report
packets within the frame.
6.4.2
Active maXStylus Report
The format of an active maXStylus report is shown in Figure 6-4. Each input report start with a
USB Report ID (1) (value 0x03).
1. The term USB Report ID should not be confused with the term Report Id as used in the Object Protocol; the two are
entirely different concepts.
35
9871EX–AT42–12/13
Figure 6-4. Active maXStylus Report Packet
Touch 1
(10 bytes)
0x03
USB
Report ID
Active
maXStylus
Data
Table 6-4 gives the detailed format of an active stylus report packet
Table 6-4.
Active maXStylus Report Format
Byte
0
Bit 7
Bit 6
Bit 5
Bit 4
USB Report ID
In Range Reserved
Bit 3
Bit 2
Bit 1
Bit 0
1
Reserved
Eraser
Barrel
Tip
2
X Position
X Center Position
Y Position
3
4
5
6
7
8
Y Center Position
Tip Pressure
9
10
• Byte 1:
Tip: 1 = Contact of the stylus with the touch screen surface, 0 = No contact
Barrel: 1 = Barrel button on, 0 = Barrel button off
Eraser: 1 = Eraser function on, 0 = Eraser function off
In Range: 1 = Stylus approaching the touchscreen detected, 0 = No stylus
approaching the touchscreen detected.
• Byte 2 to 3:
X position
• Byte 4 to 5:
X center position
• Byte 6 to 7:
Y position
• Byte 8 to 9:
Y center position
• Byte 10:
Tip Pressure: Force exerted against the touch screen surface by the stylus.
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mXT1664S1
6.5
Interface 1 (Generic HID)
Interface 1 is a Generic Human Interface Device, compliant with HID specification 1.11 with
amendments. (1)
It consists of two endpoints: an interrupt-In endpoint (Endpoint 1) and an interrupt-out endpoint
(Endpoint 2). The data packet in each case contains a 1-byte USB Report ID followed by 63
bytes of data, totalling 64 bytes (see Figure 6-5).
Figure 6-5. Data Packet for Interface 1
0x01
Data 0
Data 1
Data 62
USB
Packet Data
Report ID
Commands are sent by the application software over the Interrupt-out endpoint, Endpoint 2.
The command is sent as the first data byte of the packet data (data byte 0), followed by
conditions and/or data.
The supported commands are as follows:
• Read/write Memory Map
• Send Auto-return messages
• Start debug monitoring
• End debug monitoring
Responses from the device are sent via the interrupt-In endpoint, Endpoint 1.
6.5.1
Read/Write Memory Map
Introduction
6.5.1.1
This command is used to carry out a write/read operation on the memory map of the device.
The USB Report ID is 0x01.
The command packet has the generic format given in Figure 6-6. The following sections give
examples on using the command to write to the memory map and to read from the memory
map.
Figure 6-6. Generic Command Packet Form
0x51
Addr0
NumWx
NumRx
Addr1
Data 0
Data 57
0x01
USB
Report ID
Command
ID
Number of Bytes
to Write / Read
Address Pointer
(LSB, MSB)
Write Data
In Figure 6-6:
• NumWx is the number of data bytes to write to the memory map (may be zero). If the
address pointer is being sent, this must include the size of the address pointer.
1. This is an implementation of Microsoft’s USB HID specification for Multitouch digitizers.
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9871EX–AT42–12/13
• NumRx is the number of data bytes to read from the memory map (may be zero).
• Addr 0 and Addr 1 form the address pointer to the memory map (where necessary; may
be zero if not needed).
• Data 0 to Data 57 are the bytes of data to be written (in the case of a write). Note that data
locations beyond the number specified by NumWx will be ignored.
The response packet has the generic format given in Figure 6-7.
Figure 6-7. Response Packet Format
NumRx
0x01
Status
Data 0
Data 60
USB
Report ID
Result Number of
Bytes Read
Read Data
In Figure 6-7:
• Status indicates the result of the command:
0x00 = read and write completed; read data returned
0x04 = write completed; no read data requested
• NumRx is the number of bytes following that have been read from the memory map (in the
case of a read). This will be the same value as NumRx in the command packet.
• Data 0 to Data 60 are the data bytes read from the memory map.
6.5.1.2
Writing To the Device
A write operation cycle to the device consists of sending a packet that contains six header
bytes. These specify the USB report ID, the Command ID, the number of bytes to read, the
number of bytes to write, and the 16-bit address pointer.
Subsequent bytes in a multibyte transfer form the actual data. These are written to the location
of the address pointer, location of the address pointer +1, location of the address pointer + 2,
and so on.
Figure 6-8 shows an example command packet to write four bytes of data to contiguous
addresses starting at 0x1234.
Figure 6-8. Example of a Four-byte Write Starting at Address 0x1234
0x01
0x06
0x00
0x34
0x12
0x96
0x9B
0xA0
0xA5
0x51
USB
Report ID
Number Number
of Bytes of Bytes
to Write to Read
Address Pointer
(LSB, MSB)
Write Data
Command
ID
In Figure 6-8:
• The number of bytes to read is set to zero as this is a write-only operation.
• The number of bytes to write is six: that is, four data bytes plus the two address pointer
bytes.
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Figure 6-9 shows the response to this command. Note that the result status returned is 0x04
(that is, the write operation was completed but no read data was requested).
Figure 6-9. Response to Example Four-byte Write
0x01
0x04
USB
Result
Report ID
6.5.1.3
Reading From the Device
A read operation consists of sending a packet that contains the six header bytes only and no
write data.
Figure 6-10 shows an example command packet to read four bytes starting at address
0x1234. Note that the address pointer is included in the number of bytes to write, so the
number of bytes to write is set to 2 as there are no other data bytes to be written.
Figure 6-10. Example of a Four-byte Read Starting at Address 0x1234
0x01
0x51
0x02
0x04
0x34
0x12
USB Command
Number Number
of Bytes of Bytes
to Write to Read
Address Pointer
(LSB, MSB)
Report ID
ID
It is not necessary to set the address pointer before every read. The address pointer is
updated automatically after every read operation, so the address pointer will be correct if the
reads occur in order.
Figure 6-11 shows the response to this command. The result status returned is 0x00 (that is
the write operation was completed and the data was returned). The number of bytes returned
will be the same as the number requested (4 in this case).
Figure 6-11. Response to Example Four-byte Read
0x01
0x00
0x04
0x96
0x9B
0xA0
0xA5
USB
Report ID
Result
Number
of Bytes
Read
Read Data
6.5.2
Send Auto-return Messages
6.5.2.1
Introduction
With this command the device can be configured to return new messages from the Message
Processor T5 object autonomously. The packet sequence to do this is shown in Figure 6-12.
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Figure 6-12. Packet Sequence for “Send Auto-return” Command.
Host Device
“Send Auto-return” Command Packet
Response Packet
Message Data Packet
Message Data Packet
:
:
Message Data Packet
Null Packet to Terminate
The USB Report ID is 0x01.
The command packet has the format given in Figure 6-13.
Figure 6-13. Command Packet Format
0x01
0x88
Res 0
Res 1
Res 2
Res 3
Res 4
Res 5
Command
ID
USB
Report ID
Reserved Bytes
(=0x00)
In Figure 6-13:
• Res 0 to Res 5 are reserved bytes with a value of 0x00.
The response packet has the format given in Figure 6-14. Note that with this command, the
command packet does not include an address pointer as the device already knows the
address of the Message Processor T5 object.
Figure 6-14. Response Packet Format
0x88
0x00
0x01
Command
Received
USB
Report ID
Once the device has responded to the command, it starts sending message data. Each time a
message is generated in the Message Processor T5 object, the device automatically sends a
message packet to the host with the data. The message packets have the format given in
Figure 6-15.
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Figure 6-15. Message Packet Format
0xFA
0x00
Rpt ID
Data 0
Data n
0x01
USB
Report ID
ID Bytes
Message
Report ID
Message Data
In Figure 6-15:
• ID Bytes identify the packet as an auto-return message packet.
• Rpt ID is the Report ID returned by the Message Processor T5 object. (1)
• Message Data bytes are the bytes of data returned by the Message Processor. The size of
the data depends on the source object for which this is the message data. Refer to the
mXT1664S 2v0 Protocol Guide for more information.
To stop the sending of the messages, the host can send a null command packet. This consists
of two bytes: a report ID of 0x01 and a command byte of 0x00 (see Figure 6-16).
Figure 6-16. Null Command Packet Format
0x01
0x00
Null
USB
Report Command
ID ID
Note that the “Start Debug Monitoring” command may also terminate any currently enabled
auto-return mode (see Section 6.5.3).
6.5.2.2
Reading Status Messages
Figure 6-10 shows an example sequence of packets to receive messages from the Message
Processor T5 object using the “Send Auto-return” command.
1. This is the Report ID used in the Object Protocol and should not be confused with the USB Report ID. Refer to the
mXT1664S 2v0 Protocol Guide for more information on the use of Report IDs in the Object Protocol.
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Figure 6-17. Example Auto-return Command Packet
Send Auto-return Command
0x88
0x00
0x00
0x00
0x00
0x00
0x01
Message Data
USB Command
Report
ID
ID
Response From Chip Set
0x01
0x88
0x00
Command
Received
Read Message Data
0x01
0xFA
0xFA
0x00
0x00
0x02
0x11
0xC0
0x03
0x1A
0x1A
0x1E
0x06
0x00
0x4F
0x00
0x1C
0x1C
0x10
0x01
0x1C
ID Bytes
Message
Report ID
Message Data
Send Null Command To Terminate
0x01
0x00
Null
6.5.3
Start Debug Monitoring
This command instructs the device to return debug-monitoring data packets using the debug
port, if this feature has been enabled in the Command Processor T6 object.
The USB Report ID can be either 0x01 or 0x02. This allows the source of the request to be
identified. The main difference is that a USB Report ID of 0x01 will terminate any currently
enabled auto-return mode (see Section 6.5.2 on page 39).
The command packet has the format given in Figure 6-18.
Figure 6-18. Command Packet Format
0x01or
0xE1
0x02
USB
Report
ID
Command
ID
The response packet has the format given in Figure 6-19. Note that the USB Report ID will be
the same as that used in the command packet.
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Figure 6-19. Response Packet Format
0x01 or
0x02
0xE1
USB
Report
ID
Command
Received
The debug data packet has the format given in Figure 6-20.
Figure 6-20. Debug Data Packet Format
Packet
Num
Num
Packets
Frame
Num
Data 0
Data 59
0x02
USB
Debug Data
Report ID
In Figure 6-20:
• PacketNum is the number of this USB packet in the debug data frame (full set of debug
data). Refer to QTAN0050, Using the maXTouch Debug Port, for more information on the
format of the debug data.
• NumPackets is the total number of USB packets that make up a debug data frame.
• FrameNum is the ID number of this frame.
• Data 0 to Data 59 are 59 bytes of debug data.
6.5.4
Stop Debug monitoring
This command instructs the device to cease returning debug-monitoring data packets.
The command packet has the following format:
The USB Report ID is either 0x01 or 0x02.
The command packet has the format given in Figure 6-21.
Figure 6-21. Command Packet Format
0x01 or
0x02
0xE2
USB
Report
ID
Command
ID
The response packet has the format given in Figure 6-22.
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Figure 6-22. Response Packet Format
0x01 or
0x02
0xE2
USB
Report
ID
Command
Received
6.6
USB Suspend Mode
When the device is used in USB configuration, the USB “System Suspend” event can be used
to minimize current consumption. Note that it is possible to put the device into deep sleep
mode without also sending a “System Suspend” event on the USB bus, but the current
consumption is not as low. The USB controller must send a USB “System Wake Up” event on
the bus to bring the device out of suspend mode.
The device can also be configured to respond to USB “Remote Wakeup” requests. In this
case, if the operating system enables remote wakeup and the device is suspended, the device
will continue to scan at a preset sensor refresh rate. Use of the remote wake up feature and
the sensor refresh rate are configured using the Digitizer HID Configuration T43 object (refer
to the mXT1664S 2v0 Protocol Guide for more information).
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7. HID-I2C-compatible Communications
7.1
Communications Protocol
The device is an HID-I2C DEVICE presenting two top-level collections (TLCs):
Interface 0 (Digitizer HID-I2C) – supplies touch information to the host. This interface is
supported by Microsoft Windows 8 without the need for additional software.
Interface 1 (Generic HID-I2C) – This interface provides a generic HID-I2C interface that allows
the host to communicate with the chipset using the object protocol.
To use the device in HID-I2C mode, the I2CMODE pin should be pulled low. Other features are
identical to standard I2C-compatible communication described in Section 5.2 on page 25.
7.2
7.3
I2C-compatible Addresses
See Section 5.2 on page 25.
Device
The device is compliant with HID-I2C specification V0.9. It has the following specification:
Vendor ID:
Product ID:
Version:
0x03EB (Atmel)
0x212C
16-bit Version & Build Identifier in the form 0xVVBB, where:
VV = Version Major (Upper 4 bits) / Minor (Lower 4 bits)
BB = Build number in BCD format
HID descriptor address:
0x0000.
7.4
Interface 0 (Digitizer HID-I2C)
Interface 0 is a digitizer class HID.
7.4.1
Normal Touch Report
The format of an input report is shown in Figure 7-1. Each input report starts with a report ID
and each input report message report contains data of one touch.
Figure 7-1. Input Report Packet
Touch 1
(14 bytes)
Scan Time
(2 bytes)
Count
0x01
HID-I2C
Report ID
Touch
Status
Data
An example of the input report packets for 3 active touches is shown in Figure 6-3 on page 34.
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Figure 7-2. Example Input Report Packets for 3 Active Touches
Touch 1
(14 bytes)
Scan Time
(2 bytes)
Count = 3
Count = 0
Count = 0
0x01
0x01
0x01
Touch 2
(14 bytes)
Scan Time
(2 bytes)
Touch 3
(14 bytes)
Scan Time
(2 bytes)
HID-I2C
Report ID
Touch
Status
Data
Each input report consists of a HID-I2C report ID followed by 17 bytes of that describe the
status of one active touch. The input report format depends on the geometry calculation field
(TCHGEOMEN) of the Digitizer HID Configuration T43 object. Table 7-2 and Table 7-2
explains the detailed format of an input report packet.
Table 7-1.
Input Report Format when TCHGEOMEN = 1
Byte
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
HID-I2C Report ID
Reserved
1
Status
2
Touch ID
3 – 4
5 – 6
7 – 8
9 – 10
11
X Position
X’ Position
Y Position
Y’ Position
Touch Width
Reserved
12
13
Touch Height
Reserved
14
15 – 16
17
Scan Time
Number of active touches to be sent in one package
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Table 7-2.
Input Report Format when TCHGEOMEN = 0
Byte
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
HID-I2C Report ID
Reserved
1
Status
2
Touch ID
3 – 4
5 – 6
7 – 8
9 – 10
11
X Position
Reserved
Y Position
Reserved
Reserved
12
Reserved
13
Reserved
14
Reserved
15 – 16
17
Scan Time
Number of active touches to be sent in one package
• Byte 2:
Touch ID: Identifies the touch for which this is a status report (starting from 0).
• Bytes 3 to 10:
X and Y positions: These are scaled to 12-bit resolution. This means that the
upper four bits of the MSByte will always be zero.
Bytes 5,6, 9, 10 are Reserved when TCHGEOMEN is set to 0.
• Byte 11:
Touch Width: Reports the width of the detected touch when TCHGEOMEN is set
to 1.
• Byte 13:
Touch Height: Reports the height of the detected touch when TCHGEOMEN is
set to 1.
• Byte 15 to 16:
Scan Time: Timestamp associated with the current report packet with a 10 kHz
resolution.
7.4.2
Active maXStylus Report
The format of an active maXStylus report packet is shown in Figure 7-3.
Figure 7-3. Example Active maXStylus Report
Touch 1
0x07
(10 bytes)
HID-I2C
Report ID
Active
maXStylus
Data
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Each active maXStylus report start with a HID-I2C Report ID (value 0x06). Table 7-3 gives the
detailed format of an active stylus report packet.
Table 7-3.
Active maXStylus Report
Byte
0
Bit 7
Bit 6
Bit 5
Bit 4
HID-I2C Report ID = 0x07
In Range Reserved
Bit 3
Bit 2
Bit 1
Bit 0
1
Reserved
Eraser
Barrel
Tip
2
X Position
3
4
X Center Position
Y Position
5
6
7
8
Y Center Position
Tip Pressure
9
10
• Byte 1:
Tip: 1 = Contact of the stylus with the touch screen surface, 0 = No contact.
Barrel: 1 = Barrel button on, 0 = Barrel button off
Eraser: 1 = Eraser function on, 0 = Eraser function off.
In Range: 1 = Stylus approaching the touchscreen detected, 0 = No stylus
approaching the touchscreen detected.
• Byte 2 to 3:
X position
• Byte 4 to 5:
X center position
• Byte 6 t o7:
Y position
• Byte 8 to 9:
Y center position
• Byte 10:
Tip Pressure: Force exerted against the touch screen surface by the stylus.
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7.5
Interface 1 (Generic HID-I2C)
Interface 1 is a generic human interface device. It supports an input report for receiving data
from the device and an output report for sending data to the device.
Commands are sent by the host using the output reports. Responses from the device are sent
using input reports.
Supported commands are:
• Read/Write Memory Map
• Send Auto-return Messages
7.5.1
Read/Write Memory Map
Introduction
7.5.1.1
This command is used to carry out a write/read operation on the memory map of the device.
The HID-I2C Report ID is 0x06.
Note: This value may change.
The command packet has the generic format given in Figure 7-4. The following sections give
examples on using the command to write to the memory map and to read from the memory
map.
Figure 7-4. Generic Command Packet Format
...
0x06
NumWx NumRx
Addr 0
Addr 1
Data 0
Data 11
0x51
HID-I2C Command
Number of Bytes
to Read/Write
Address Pointer
(LSB, MSB)
Write Data
Report ID
ID
In Figure 7-4:
• NumWx is the number of data bytes to write to the memory map (may be zero). If the
address pointer is being sent, this must include the size of the address pointer.
• NumRx is the number of data bytes to read from the memory map (may be zero).
• Addr 0 and Addr 1 form the address pointer to the memory map (where necessary; may
be zero if not needed).
• Data 0 to Data 11 are the bytes of data to be written (in the case of a write). Note that data
locations beyond the number specified by NumWx will be ignored.
The response packet has the generic format given in Figure 7-5.
Figure 7-5. Response Packet Format
...
0x06
NumRx
Data 0
Data 14
Status
HID-I2C
Report ID
Success/ Number of
Bytes Read
Read Data
Failure
In Figure 7-5 on page 49:
• Status indicates the result of the command:
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0x00 = read and write completed; read data returned
0x04 = write completed; no read data requested
• NumRx is the number of bytes following that have been read from the memory map (in the
case of a read). This will be the same value as NumRx in the command packet.
• Data 0 to Data 14 are the data bytes read from the memory map.
7.5.1.2
Writing To the Device
A write operation cycle to the device consists of sending a packet that contains six header
bytes. These specify the HID-I2C report ID, the Command ID, the number of bytes to read, the
number of bytes to write, and the 16-bit address pointer.
Subsequent bytes in a multibyte transfer form the actual data. These are written to the location
of the address pointer, location o
If the address pointer +1, location of the address pointer + 2, and so on.
Figure 7-6 shows an example command packet to write four bytes of data to contiguous
addresses starting at 0x1234.
Figure 7-6. Example of a Four-byte Write Starting at Address 0x1234
0x06
0x06
0x00
0x34
0x12
0x96
0x9B
0xA0
0xA5
0x51
2
HID-I C
Number Number
of Bytes of Bytes
to Write to Read
Address Pointer
(LSB, MSB)
Write Data
Command
ID
Report ID
In Figure 7-6:
• The number of bytes to read is set to zero as this is a write-only operation.
• The number of bytes to write is six: that is, four data bytes plus the two address pointer
bytes.
Figure 7-7 shows the response to this command. Note that the result status returned is 0x04
(that is, the write operation was completed but no read data was requested).
Figure 7-7. Response to Example Four-byte Write
0x06
0x04
HID-I2C
Result
Report ID
7.5.1.3
Reading From the Device
A read operation consists of sending a packet that contains the six header bytes only and no
write data.
Figure 7-8 shows an example command packet to read four bytes starting at address 0x1234.
Note that the address pointer is included in the number of bytes to write, so the number of
bytes to write is set to 2 as there are no other data bytes to be written.
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Figure 7-8. Example of a Four-byte Read Starting at Address 0x1234
0x06 0x51 0x02 0x04 0x34 0x12
HID-I2C Command
Number Number
of Bytes of Bytes
to Write to Read
Address Pointer
(LSB, MSB)
Report ID
ID
It is not necessary to set the address pointer before every read. The address pointer is
updated automatically after every read operation, so the address pointer will be correct if the
reads occur in order.
Figure 7-9 shows the response to this command. The result status returned is 0x00 (that is the
write operation was completed and the data was returned). The number of bytes returned will
be the same as the number requested (4 in this case).
Figure 7-9. Response to Example Four-byte Read
0x06
0x00
0x04
0x96
0x9B
0xA0
0xA5
HID-I2C
Report ID
Result
Number
of Bytes
Read
Read Data
7.5.2
Send Auto-return Messages
7.5.2.1
Introduction
With this command the device can be configured to return new messages from the Message
Processor object autonomously. The packet sequence to do this is shown in Figure 7-10.
Figure 7-10. Packet Sequence for “Send Auto-return” Command.
Host
Device
“Send Auto-return” Command Packet
Response Packet
Message Data Packet
Message Data Packet
:
:
Message Data Packet
Null Packet to Terminate
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The HID-I2C Report ID is 0x06.
The command packet has the format given in Figure 7-11 on page 52.
Figure 7-11. Command Packet Format
0x06
Res 0
Res 1
Res 2
Res 3
Res 4
Res 5
0x88
HID-I2C Command
Reserved Bytes
(=0x00)
Report ID
ID
In Figure 7-11:
• Res 0 to Res 5 are reserved bytes with a value of 0x00.
The response packet has the format given in Figure 7-12. Note that with this command, the
command packet does not include an address pointer as the device already knows the
address of the Message Processor object.
Figure 7-12. Response Packet Format
0x06
0x00
0x88
HID-I2C
Report ID
Command
Received
Once the device has responded to the command, it starts sending message data. Each time a
message is generated in the Message Processor object, the device automatically sends a
message packet to the host with the data. The message packets have the format given in
Figure 7-13.
Figure 7-13. Message Packet Format
...
0x06
0x00
Rpt ID
Data 0
Data n
0xFA
HID-I2C
Report ID
ID Bytes
Message
Report ID
Message Data
In Figure 7-13:
• ID Bytes identify the packet as an auto-return message packet.
• Rpt ID is the Report ID returned by the Message Processor object. (1)
• Message Data bytes are the bytes of data returned by the Message Processor. The size of
the data depends on the source object for which this is the message data. Refer to the
mXT1664S 2v0 Protocol Guide for more information.
To stop the sending of the messages, the host can send a null command packet. This consists
of two bytes: a report ID of 0x01 and a command byte of 0x00 (see Figure 7-13).
1. This is the Report ID used in the Object Protocol and should not be confused with the USB Report ID. Refer to the
mXT1664S 2v0 Protocol Guide for more information on the use of Report IDs in the Object Protocol.
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Figure 7-14. Null Command Packet Format
0x06
0x00
HID-I2C
Report ID
Null
Command
ID
Note that any read or write will also terminate any currently enabled auto-return mode (see
“Start Debug Monitoring” on page 42).
7.5.2.2
Reading Status Messages
Figure 7-15 shows an example sequence of packets to receive messages from the Message
Processor object using the “Send Auto-return” command.
Figure 7-15. Example Auto-return Command Packet
Send Auto-return Command
0x06
0x88
0x00
0x00
0x00
0x00
0x00
HID-I2C Command
Reserved
Report
ID
ID
Response From Chip Set
0x06 0x00
0x88
0x00
0x00
0x00
0x00
Command
Received
Reserved
Read Message Data
0x06
0xFA
0xFA
0x00
0x00
0x02
0x11
0xC0
0x03
0x1C
0x1C
0x1A
0x1A
0x1E
0x1C
0x06
0x00
0x4F
0x00
0x10
0x06
ID Bytes
Message
Report ID
Message Data
Send Null Command To Terminate
0x06
0x00
Null
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7.6
CHG Line
SDA, SCL
The CHG line is an active-low, open-drain output that is used to alert the host that a new
message is available in the Input Buffer. This provides the host with an interrupt-style interface
with the potential for fast response times. It reduces the need for wasteful I2C-compatible
communications.
Further information on the CHG line is given in Section 5.7 on page 29.
7.7
7.8
7.9
Identical to standard I2C-compatible operation. Refer to Section 5.8 on page 31.
Clock Stretching
Identical to standard I2C-compatible operation. Refer to Section 5.9 on page 31.
Power Control
The mXT1664S1 supports the use of the HID-I2C “SET POWER” commands to put the device
into a low power state analogous to the USB “SUSPEND” command.
7.10 Microsoft Windows 8 Compliance
The mXT1664S1 has algorithms within the Digitizer HID Configuration T43 and Multiple Touch
Touchscreen T9 specifically to ensure Microsoft Windows 8 compliance.
The device also supports Microsoft Touch Hardware Quality Assurance (THQA) in the Serial
Data Command T68 object. Refer to the Microsoft whitepaper How to Design and Test
Multitouch Hardware Solutions for Windows 8.
These, and other device features, may need specific tuning.
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8. Getting Started with mXT1664S1
8.1
Establishing Contact
8.1.1
Communication with the Host
The host can use either the I2C-compatible interface (see Section 5.1 on page 25), USB
interface (see Section 6.1 on page 32) or the HID-I2C interface ( see Section 7 on page 45) to
communicate with the device.
8.1.2
I2C-compatible Interface
On power-up, the CHG line goes low to indicate that there is new data to be read from the
Message Processor T5 object. If the CHG line does not go low, there is a problem with the
device.
The host should attempt to read any available messages to establish that the device is present
and running following power-up or a reset. Examples of messages include reset or calibration
messages. The host should also check that there are no configuration errors reported.
8.1.3
USB Interface
The host can establish contact with the device as specified in the USB 2.0 specification and
the USB HID specification (both available from www.usb.org).
8.1.4
HID-I2C Interface
The host can use the HID-I2C interface by connecting the I2CMODE pin to GND.
8.2
Using the Object Protocol
The device has an object-based protocol that is used to communicate with the device. Typical
communication includes configuring the device, sending commands to the device, and
receiving messages from the device. Refer to the mXT1664S 2v0 Protocol Guide for more
information.
The host must perform the following initialization so that it can communicate with the device:
1. Read the start positions of all the objects in the device from the Object Table and
build up a list of these addresses.
2. Use the Object Table to calculate the report IDs so that messages from the device
can be correctly interpreted.
8.3
Writing to the Device
There are three mechanisms for writing to the device:
• Using an I2C-compatible write operation (see Section 5.3 on page 25).
• Using the USB Generic HID write operation (see Section 6.5.1.2 on page 38).
• Using the Generic HID-I2C write operation (see Section 7.5.1.2 on page 50).
To communicate with the device, you write to the appropriate object:
• To send a command to the device, you write the appropriate command to the Command
Processor T6 object (refer to the mXT1664S 2v0 Protocol Guide).
• To configure the device, you write to an object. For example, to configure the device’s
power consumption you write to the global Power Configuration T7 object, and to set up a
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touchscreen you write to a Multiple Touch Touchscreen T9 object. Some objects are
optional and need to be enabled before use. Refer to the mXT1664S 2v0 Protocol Guide
for more information on the objects.
8.4
Reading from the Device
Status information is stored in the Message Processor T5 object. This object can be read to
receive any status information from the device. There are two mechanisms that provide an
interrupt-style interface for reading messages in the Message Processor T5 object:
• When using the I2C-compatible interface, the CHG line is asserted whenever a new
message is available in the Message Processor T5 object (see Section 5.7 on page 29).
See Section 6.5.1.3 on page 39 for information on the format of the I2C-compatible read
operation.
• When using the USB interface, the Generic HID interface provides an interrupt-driven
interface that sends the messages automatically (see Section 6.5.2 on page 39).
• When using the HID-I2C interface, the Generic HID-I2C interface provides an interrupt-
driven interface that sends the messages automatically (see Section 7.5.1.3 on page 50)
Note that in both cases the host should always wait to be notified of messages. The host
should not poll the device for messages.
The USB Digitizer HID provides a third alternative interrupt-style mechanism for reading a
subset of the touch data. See Section 6.4 on page 33 for more information.
8.5
Configuring the Device
The objects are designed such that a default value of zero in their fields is a “safe” value that
typically disables functionality. The objects must be configured before use and the settings
written to the nonvolatile memory using the Command Processor T6 object.
Perform the following actions for each object:
1. Enable the object, if the object requires it.
2. Configure the fields in the object, as required.
3. Enable reporting, if the object supports messages, to receive messages from the
object.
Refer to the mXT1664S 2v0 Protocol Guide for more information on configuring the objects.
The following objects are read-only and require no configuration:
• Debug Objects
– Diagnostic Debug T37
• General objects:
– Message Processor T5
• Support objects:
– User Data T38
– Message Count T44
The following objects must be configured before use:
• General objects
– Power Configuration T7
– Acquisition Configuration T8
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The following objects should be checked and configured as necessary:
• General objects:
– Command Processor T6
• Support objects:
– Communications Configuration T18
– GPIO/PWM Configuration T19
– CTE Configuration T46
The following objects should also be enabled and configured, as required:
• Touch objects:
– Multiple Touch Touchscreen T9
– Key Array T15
• Signal processing objects:
– Grip Suppression T40
– Stylus T47
– One-touch Gesture Processor T24
– Two-touch Gesture Processor T27
– Touch Suppression T42
– Adaptive Threshold T55
– SlimSensor T56
– Extra Touchscreen Data T57
– maXCharger T62
– Active Stylus T63
– Lens Bending T65
– Zone Indication T73
• Support objects:
– Digitizer HID Configuration T43
– Self Test T25
– Timer T61
– maXStartup T66
– Serial Data Command T68
– Dynamic Configuration Controller T70
– Dynamic Configuration Container T71
– CTE_SCAN Configuration T77
– Touch Event Trigger T79
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9. Specifications
See Appendix B on page 76 for the reference configuration.
9.1
Absolute Maximum Specifications
Vdd
3.6 V
12 V
3.6 V
XVdd
AVdd
Vdd Core (for 1.8V I2C-compatible mode only)
Max continuous pin current, any control or drive pin
Voltage forced onto any pin
1.98 V
20 mA
–0.3 V to (Vdd or AVdd) + 0.3 V
10,000
Configuration parameters maximum writes
CAUTION: Stresses beyond those listed under Absolute Maximum Specifications may cause permanent damage to the
device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated
in the operational sections of this specification is not implied. Exposure to absolute maximum specification conditions for
extended periods may affect device reliability.
9.2
Recommended Operating Conditions
Operating temp
Storage temp
–40°C to +85°C
–60°C to +150°C
1.8 V –5% +10% (I2C-compatible 1.8 V mode)
2.7 V to 3.3 V 10% (I2C-compatible mode)
3.0 V to 3.3 V 10% (USB mode)
2.7 to 3.3 V 10%
Vdd External
AVdd
XVdd
2.7 to 10.0 V 5%
Vdd vs AVdd power sequencing
Vdd vs XVdd power sequencing
Vdd supply ripple
XVdd supply ripple
AVdd supply ripple
No sequencing required
XVdd must not be powered before Vdd
50 mV 1 Hz to 1 MHz
25 mV 1 Hz to 1MHz
25 mV 1 Hz to 1 MHz
0.95 pF to 4.8 pF, when XVdd = 2.5 V to 4.75 V
0.5 pF to 4.8 pF, when XVdd = 4.75 V to 10 V
Cx transverse load capacitance per channel
Temperature slew rate
10°C/min
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9.3
DC Characteristics
9.3.1
Digital Voltage Supply
Parameter
Description
Min
1.71
2.43
2.7
Typ
Max
3.6
3.6
3.6
2.5
Units
V
Notes
I2C-compatible 1.8 V mode
I2C-compatible mode
USB mode
Vdd
Operating limits
V
V
Rate of rise
Rate of rise
0.002
V/µs
9.3.2 Analog Voltage Supply
Parameter
AVdd
Rate of rise
Description
Operating limits
Rate of rise
Min
2.5
Typ
Max
3.6
Units
V
Notes
Section 4.6.3 on page 22
0.002
2.5
V/µs
9.3.3
XVdd Supply
Parameter
XVdd
Description
Min
2.5
2
Typ
Max
10.5
30
Units
V
Notes
Operating limits
Rate of rise
10.0
Rate of rise
V/ms
Note: The rate of rise values must be followed to avoid permanent damage to the
device.
9.3.4
Parameter
Input (RESET, SDA, SCL)
Input/Output Characteristics
Description
Min
Typ
Max
Units
Notes
Vil
Low input logic level
–0.3
0.3 × Vdd
Vdd + 0.3
1
V
V
Vdd = 1.8 V to 3.3 V
Vdd = 1.8 V to 3.3 V
Pull-up resistors disabled
Vih
Iil
High input logic level
Input leakage current
0.7 × Vdd
µA
Output (CHG)
Vdd = 3 V, IOL = 2.7 mA, High
Drive Enabled
Vdd = 3 V, IOL = 1.35 mA
Vol
Low output voltage
High output voltage
0.2 × Vdd
V
V
Vdd = 3 V, IOH = 2.7 mA, High
Drive Enabled
Voh
0.8 × Vdd
Vdd = 3 V, IOH = 1.35 mA
9.4
ESD Information
Parameter
Value
2000 V
Reference standard
MIL– STD883 Method 3015.7
Electrostatic Discharge HBM
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9.5
Supply Current
AVdd = 2.75 V, Vdd = 2.69 V, XVdd = 6 V, SlimSensor T56: Optimal integration enabled, Lens Bending T65 enabled
9.5.1
Analog Supply – I2C-compatible Interface
Parameter
Description
Min
Typ
Max
Max
Max
Units
Notes
33.65
mA
100 Hz, 1 Touch
Active average supply current
100 Hz, 1 Touch
CTE_SCAN Configuration T77=On
22.28
4.45
mA
mA
mA
mA
mA
16 Hz, no touches
AIdd
Idle average supply current
16 Hz, no touches
CTE_SCAN Configuration T77=On
1.02
0.002
0.004
Sleep average supply current
CTE_SCAN Configuration
T77=On
9.5.2
Analog Supply – USB Bus
Parameter
Description
Min
Typ
Units
Notes
30.22
mA
100 Hz, 1 Touch
Active average supply current
100 Hz, 1 Touch
CTE_SCAN Configuration T77=On
21.61
4.13
mA
mA
mA
mA
mA
16 Hz, no touches
AIdd
Idle average supply current
Sleep average supply current
16 Hz, no touches
CTE_SCAN Configuration T77=On
0.91
0.002
0.004
CTE_SCAN Configuration
T77=On
9.5.3
Digital Supply – I2C-compatible Interface
Parameter
Description
Min
Typ
Units
Notes
15.08
mA
100 Hz, 1 Touch
Active average supply current
100 Hz, 1 Touch
CTE_SCAN Configuration T77=On
14.08
2.19
1.06
0.15
0.15
mA
mA
mA
mA
mA
16 Hz, no touches
DIdd
Idle average supply current
Sleep average supply current
16 Hz, no touches
CTE_SCAN Configuration T77=On
CTE_SCAN Configuration
T77=On
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9.5.4
Digital Supply – USB Bus
Parameter
Description
Min
Typ
Max
Max
Max
Units
Notes
17.88
mA
100 Hz, 1 Touch
Active average supply current
100 Hz, 1 Touch
CTE_SCAN Configuration T77=On
16.97
11.52
12.19
11.46
12.69
mA
mA
mA
mA
mA
16 Hz, no touches
DIdd
Idle average supply current
Sleep
16 Hz, no touches
CTE_SCAN Configuration T77=On
CTE_SCAN Configuration
T77=On
9.5.5
X Drive Supply – I2C-compatible Interface
Parameter
Description
Min
Typ
Units
Notes
0.97
mA
100 Hz, 1 Touch
Active average supply current
100 Hz, 1 Touch
CTE_SCAN Configuration T77=On
0.82
0.68
mA
mA
mA
mA
mA
16 Hz, no touches
XIdd
Idle average supply current
Sleep average supply current
16 Hz, no touches
CTE_SCAN Configuration T77=On
0.66
0.001
0.0005
CTE_SCAN Configuration
T77=On
9.5.6
X Drive Supply – USB Bus
Parameter
Description
Min
Typ
Units
Notes
0.93
mA
100 Hz, 1 Touch
Active average supply current
100 Hz, 1 Touch
CTE_SCAN Configuration T77=On
0.85
0.69
0.66
mA
mA
mA
16 Hz, no touches,
XIdd
Idle average supply current
Sleep
16 Hz, no touches
CTE_SCAN Configuration T77=On
0.0002
0.0006
mA
mA
CTE_SCAN Configuration T77=On
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9.5.7
Analog Current– Lens Bending T65 Disabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 disabled
I2C-compatible
USB
70.0000
70.0000
60.0000
50.0000
40.0000
30.0000
20.0000
10.0000
0.0000
AIdd No Touch
AIdd 1 Touch
AIdd No Touch
AIdd 1 Touch
60.0000
50.0000
40.0000
30.0000
20.0000
10.0000
0.0000
AIdd 5 Touches
AIdd 10 Touches
AIdd 5 Touches
AIdd 10 Touches
Acquisition Interval (ms)
Acquisition Interval (ms)
9.5.8
Analog Current – Lens Bending T65 Enabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 enabled
I2C-compatible
USB
70.0000
70.0000
60.0000
50.0000
40.0000
30.0000
20.0000
10.0000
0.0000
AIdd No Touch
AIdd 1 Touch
AIdd No Touch
AIdd 1 Touch
60.0000
50.0000
40.0000
30.0000
20.0000
10.0000
0.0000
AIdd 5 Touches
AIdd 10 Touches
AIdd 5 Touches
AIdd 10 Touches
Acquisition Interval (ms)
Acquisition Interval (ms)
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9.5.9
Analog Current – CTE_SCAN Configuration T77 (XZoom and Precision Scan) Enabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 enabled
I2C-compatible
USB
70.0000
70.0000
60.0000
50.0000
40.0000
30.0000
20.0000
10.0000
0.0000
AIdd No Touch
AIdd 1 Touch
AIdd No Touch
AIdd 1 Touch
60.0000
50.0000
40.0000
30.0000
20.0000
10.0000
0.0000
AIdd 5 Touches
AIdd 10 Touches
AIdd 5 Touches
AIdd 10 Touches
Acquisition Interval (ms)
Acquisition Interval (ms)
9.5.10
Digital Current – Lens Bending T65 Disabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 disabled
I2C-compatible
USB
30.0000
25.0000
20.0000
15.0000
10.0000
5.0000
30.0000
25.0000
20.0000
15.0000
10.0000
5.0000
DIdd No Touch
DIdd 1 Touch
DIdd No Touch
DIdd 1 Touch
DIdd 5 Touches
DIdd 10 Touches
DIdd 5 Touches
DIdd 10 Touches
0.0000
0.0000
Acquisition Interval (ms)
Acquisition Interval (ms)
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9.5.11
Digital Current – Lens Bending T65 Enabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 enabled
I2C-compatible
USB
30.0000
25.0000
20.0000
15.0000
10.0000
5.0000
30.0000
25.0000
20.0000
15.0000
10.0000
5.0000
DIdd No Touch
DIdd 1 Touch
DIdd No Touch
DIdd 1 Touch
DIdd 5 Touches
DIdd 10 Touches
DIdd 5 Touches
DIdd 10 Touches
0.0000
0.0000
Acquisition Interval (ms)
Acquisition Interval (ms)
9.5.12
Digital Current – CTE_SCAN Configuration T77 (XZoom and Precision Scan) Enabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 enabled
I2C-compatible
USB
30.0000
25.0000
20.0000
15.0000
10.0000
5.0000
30.0000
25.0000
20.0000
15.0000
10.0000
5.0000
DIdd No Touch
DIdd 1 Touch
DIdd No Touch
DIdd 1 Touch
DIdd 5 Touches
DIdd 10 Touches
DIdd 5 Touches
DIdd 10 Touches
0.0000
0.0000
Acquisition Interval (ms)
Acquisition Interval (ms)
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9.5.13
XIdd – Lens Bending T65 Disabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 disabled
I2C-compatible
USB
1.4000
1.2000
1.0000
0.8000
0.6000
0.4000
0.2000
0.0000
1.4000
1.2000
1.0000
0.8000
0.6000
0.4000
0.2000
0.0000
XIdd No Touch
XIdd 1 Touch
XIdd No Touch
XIdd 1 Touch
XIdd 5 Touches
XIdd 10 Touches
XIdd 5 Touches
XIdd 10 Touches
Acquisition Interval (ms)
Acquisition Interval (ms)
9.5.14
XIdd – Lens Bending T65 Enabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 enabled
I2C-compatible
USB
1.4000
1.2000
1.0000
0.8000
0.6000
0.4000
0.2000
0.0000
1.4000
1.2000
1.0000
0.8000
0.6000
0.4000
0.2000
0.0000
XIdd No Touch
XIdd 1 Touch
XIdd No Touch
XIdd 1 Touch
XIdd 5 Touches
XIdd 10 Touches
XIdd 5 Touches
XIdd 10 Touches
Acquisition Interval (ms)
Acquisition Interval (ms)
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9.5.15
XIdd – CTE_SCAN Configuration T77 (XZoom and Precision Scan) Enabled
XSIZE = 30, YSIZE = 18, CHRGTIME = 132, IDLESYNCSPERX = ACTVSYNCSPERX = 16, SlimSensor T56 : Optimal integration enabled,
Pipelining enabled, Lens Bending T65 enabled
I2C-compatible
USB
1.4000
1.2000
1.0000
0.8000
0.6000
0.4000
0.2000
0.0000
1.4000
1.2000
1.0000
0.8000
0.6000
0.4000
0.2000
0.0000
XIdd No Touch
XIdd 1 Touch
XIdd 5 Touches
XIdd 10 Touches
XIdd No Touch
XIdd 1 Touch
XIdd 5 Touches
XIdd 10 Touches
Acquisition Interval (ms)
Acquisition Interval (ms)
9.6
Timing Specifications
9.6.1
Touch Latency
Description
Min
4.0
4.0
4.0
Typ
9.8
8.7
5.2
Max
Units
ms
Notes
80 Hz
15.7
13.4
6.4
TCHDI = 0
IDLESYNCSPERX/
ACTSYNCSPERX = 8
100 Hz
200 Hz
ms
ms
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9.6.2
Speed
XSIZE = 32, YSIZE = 52, CHRGTIME = 120 (2.5 µs), IDLESYNCSPERX = ACTVSYNCSPERX = 8,
SlimSensor T56 = Off, maXCharger T62 = off, Lens Bending T65 = Off
350
300
250
200
150
100
50
Pipelining = Off
Pipelining = On
0
1
2
3
4
5
6
7
8
9
10
Number of Moving Touches
9.7
I2C-compatible Specifications
(1)
Parameter
Value
Addresses
0x4A or 0x4B
1.7 MHz
Maximum bus speed (SCL)
I2C specification
Version 2.1
1 kΩ to 10 kΩ
1 kΩ to 3 kΩ
Required pull-up resistance for standard mode (100 kHz)
Required pull-up resistance for fast mode (400 kHz)
Required pull-up resistance for high-speed mode (1.7 MHz) 0.5 kΩ to 0.75 kΩ
1. Refer to mXT1664S 2v0 Protocol Guide for bootloader specific information.
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9.8
USB Specification
Parameter
Operation
0x81 (Endpoint 1)
0x02 (Endpoint 2)
0x83 (Endpoint 3)
Endpoint Addresses
Maximum bus speed
Vendor ID
12 Mbps
0x03EB (Atmel)
0x212C (mXT1664S1)
Product ID
USB 2.0
USB specification
HID specification 1.11 with amendments for multitouch digitizers
9.9
HID-I2C Specification
Parameter
Operation
Vendor ID
0x03EB (Atmel)
0x212C (mXT1664S1)
0.9
Product ID
HID-I2C specification
9.10 Touch Accuracy and Repeatability
Parameter
Linearity
Min
Typ
0.5
1
Max
Units
mm
mm
mm
%
Notes
Accuracy
Accuracy at edge
Repeatability
2
0.25
X axis with 12-bit resolution
9.11 Power Supply and Ripple Noise
Parameter
Min
Typ
Max
Units
Notes
Across frequency range
1 Hz to 1 MHz
Vdd
50
mV
Across frequency range
1 Hz to 1 MHz
XVdd and AVdd
XVdd and AVdd
25
40
mV
mV
Across frequency range
1 Hz to 1 MHz, with Noise
Suppression enabled
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9.12 Thermal Packaging
9.12.1
Thermal Data
Parameter
Typ
33.7
5.0
Unit
°C/W
°C/W
Condition
Package
Junction to ambient thermal resistance
Junction to case thermal resistance
Still air
VFBGA 128, 7 X 7 mm
VFBGA 128, 7 X 7 mm
9.12.2
Junction Temperature
The average chip junction temperature, TJ in °C can be obtained from the following:
T
= T + (P × θ
)
JA
J
A
D
If a cooling device is required, use this equation:
= T + (P × (θ + θ ))
T
J
A
D
HEATSINK
JC
where:
• θJA= package thermal resistance, Junction to ambient (°C/W).
• θJC = package thermal resistance, Junction to case thermal resistance (°C/W).
• θHEATSINK = cooling device thermal resistance (°C/W), provided in the cooling device
datasheet.
• PD = device power consumption (W).
• TA is the ambient temperature (°C).
9.13 Soldering Profile
Profile Feature
Green Package
Average Ramp-up Rate (217°C to Peak)
Preheat Temperature 175°C 25°C
Time Maintained Above 217°C
Time within 5°C of Actual Peak Temperature
Peak Temperature Range
3°C/s max
150 – 200°C
60 – 150 s
30 s
260°C
Ramp down Rate
6°C/s max
8 minutes max
Time 25°C to Peak Temperature
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9.14 Mechanical Dimensions
9.14.1
128-ball 7 x 7 x 1 mm
Package Drawing Contact:
packagedrawings@atmel.com
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9.15 Part Marking
Ball A1 ID
ATMEL
Abbreviation of
Part Number
MXT1664S1
-CU
Date
(year and week)
Country Code
Die Revision
YYWWV CC
LOTCODE
Lot Code
(variable text)
9.16 Part Numbers
Part Number
QS Number
Description
ATMXT1664S1-CUR
(supplied in tape and reels)
128-ball 7 x 7 mm VFBGA RoHS
compliant
QS777
ATMXT1664S1-CU
(supplied in trays)
128-ball 7 x 7 mm VFBGA RoHS
compliant
QS777
9.17 Silicon Revision Identification
Silicon Revision
REVID
Notes
E
F
4
5
6
Refer to the mXT1664S 2v0 Protocol
Guide for more information on how to read
data from the Diagnostic Debug T37
object.
G
9.18 Moisture Sensitivity Level (MSL)
MSL Rating
Peak Body Temperature
Specifications
MSL3
260oC
IPC/JEDEC J-STD-020
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Appendix A. PCB Design Considerations
A.1 Introduction
The following sections give the design considerations that should be adhered to when
designing a PCB layout for use with the mXT1664S1. Of these, power supply and ground
tracking considerations are the most critical.
By observing the following design rules, and with careful preparation for the PCB layout
exercise, designers will be assured of a far better chance of success and a correctly
functioning product.
A.2 Printed Circuit Board
Atmel recommends the use of a four layer printed circuit board for mXT1664S1 applications.
This, together with careful layout, will ensure that the board meets relevant EMC requirements
for both noise radiation and susceptibility, as laid down by the various national and
international standards agencies.
A.3 Supply Rails and Ground Tracking
Power supply and clock distribution are the most critical parts of any board layout. Because of
this, it is advisable that these be completed before any other tracking is undertaken. After
these, supply decoupling, and analog and high speed digital signals should be addressed.
Track widths for all signals, especially power rails should be kept as wide as possible in order
to reduce inductance.
The Power and Ground planes themselves can form a useful capacitor. Flood filling for either
or both of these supply rails, therefore, should be used where possible. It is important to
ensure that there are no floating copper areas remaining on the board: all such areas should
be connected to the 0 V plane. The flood filling should be done on the outside layers of the
board.
In applications where the USB bus supplies power to the board, care should be taken to
ensure that suitable capacitive decoupling is provided close to the USB connector. The
tracking to the on-board regulators should also be kept as short as possible.
It should also be remembered that the screen of the USB cable is not intended to be
connected to the ground or 0V supply of a remote device. It should either be left open circuit
(being connected only at the host computer end) or decoupled with a suitable high voltage
capacitor (typically 4.7 nF – 250 V) and a parallel resistor (typically 1 MΩ). Note that these
components may not be required when the USB cabling is internal and permanently wired,
and is routed away from the noisier parts of the system.
A.4 Power Supply Decoupling
As a rule, a suitable decoupling capacitor should be placed on each and every supply pin on
all digital devices. It is important that these capacitors are placed as close to the chip’s supply
pins as possible (less than 5mm away). The ground connection of these capacitors should be
tracked to 0V by the shortest, heaviest traces possible.
Capacitors with a Type II dielectric, such as X5R or X7R and with a value of at least 100nF,
should be used for this purpose.
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In addition, at least one ‘bulk’ tantalum decoupling capacitor, with a minimum value of 4.7 µF
should be placed on each power rail, close to where the supply enters the board.
Surface mounting capacitors are preferred to wire leaded types due to their lower ESR and
ESL. It is often possible to fit these decoupling capacitors underneath and on the opposite side
of the PCB to the digital ICs. This will provide the shortest tracking, and most effective
decoupling possible.
Refer to the application note Selecting Decoupling Capacitors for Atmel’s PLDs (doc0484.pdf;
available on Atmel’s website) for further general information on decoupling capacitors.
Refer to the application note QTAN0094: mXT1664S PCB/FPCB Layout Guidelines for more
information on PCB/FPCB layout.
A.5 Suggested Voltage Regulator Manufacturers
The AVdd supply stability is critical for the device because this supply interacts directly with
the analog front end. Atmel therefore recommends that the supply for the analog section of the
board be supplied by a regulator that is separate from the logic supply regulator. This reduces
the amount of noise injected into the sensitive, low signal level parts of the design.
A single low value series resistor (around 1Ω) is required from the regulator output to the
analog supply input on the device. This, together with the regulator output capacitor, and the
capacitors at the DC input to the device, forms a simple filter on the supply rail.
A low noise device should be chosen for the regulator. If possible this should have provision
for adding a capacitor across the internal reference for further noise reduction. Reference
should be made to the manufacturer’s datasheet.
The voltage regulators listed in Table 9-1 have been tested and found to work well with the
mXT1664S1. They have compatible footprints and pin-out specifications, and are available in
the SOT-23 package.
Table 9-1.
Recommended Voltage Regulators
Manufacturer
Pin
Part Number
TLV70028
LT1761
Texas Instruments
Linear Technology
Micrel
AVdd
Vdd
Vdd
MIC5255
LP2981
National Semiconductor
Torex
Vdd
Vdd
XC6204
AS1340
AMS
XVdd
XVdd
GMMT
G5126
Note some manufacturers claim that minimal or no capacitance is required for correct
regulator operation. However, in all cases, a minimum of a 1.0 µF ceramic, low ESR capacitor
at the input and output of these devices should be used. The manufacturers’ datasheets
should always be referred to when selecting capacitors for these devices and the typical
recommended values, types and dielectrics adhered to.
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Figure 9-1. Example Regulator Circuit
ELL4LG100MA
Vdd
Vbatt
XVdd
IN
LX
4µ7
2n2
10µF
OVP
G5126
EN
FB
GND
Note that a “soft-start” regulator with excellent noise and load step regulation will be needed to
satisfy the XVdd supply requirements. 1% resistors should be used to define the nominal
output voltage. If 5% resistors are used, the nominal XVdd voltage must be reduced
accordingly to ensure that the recommended voltage range is adhered to. Figure 9-1 provides
an example circuit for the XVdd supply.
A.6 Crystal Oscillator
If a crystal oscillator is used, its placement is critical to the performance of the design. The
connecting leads between the device and the crystal should be as short as possible. These
tracks, together with the crystal itself, should be placed above a suitable ground plane. It is
also important that no other signal tracks are placed close to, or under, these tracks. The
crystal input pins are at a relatively high impedance and cross-talk from other signals will
seriously affect oscillator stability and accuracy. The crystal’s case should also be connected
to ground if possible.
If an oscillator module is used, care still needs to be taken when tracking to the device. The
clock signal should be kept as short as possible, with a solid ground return underneath the
clock output.
A.7 Analog I/O
In general, tracking for the analog I/O signals from the device should be kept as short as
possible. These normally go to a connector which interfaces directly to the touchscreen.
Ensure that adequate ground-planes are used. An analog ground plane should be used in
addition to a digital one. Care should be taken to ensure that both ground planes are kept
separate and are connected together only at the point of entry for the power to the PCB. This
is usually at the input connector.
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A.8 Component Placement
It is important to orient all devices so that the tracking for important signals (such as power and
clocks) are kept as short as possible. This simple point is often overlooked when initially
planning a PCB layout and can save hours of work at a later stage.
A.9 Digital Signals
In general, when tracking digital signals, it is advisable to avoid sharp directional changes,
sensitive signal tracks (such as analog I/O) and any clock or crystal tracking.
A good ground return path for all signals should be provided, where possible, to ensure that
there are no discontinuities in the ground return path.
A.10 EMC and Other Observations
The following recommendations are not mandatory, but may help in situations where
particularly difficult EMC or other problems are present:
• A small common mode choke is recommended on the differential USB data pair. This
should be placed directly at the USB connector, between the connector and the relevant
pins. Tracking lengths for the USB data pair should be kept as short as possible.
• Try to keep as many signals as possible on the inside layers of the board. If suitable ground
flood fills are used on the top and bottom layers, these will provide a good level of
screening for noisy signals, both into and out of the PCB.
• Ensure that the on-board regulators have sufficient tracking around and underneath the
devices to act as a heatsink. This heatsink will normally be connected to the 0V or ground
supply pin. Increasing the width of the copper tracking to any of the device pins will aid in
removing heat. There should be no solder mask over the copper track underneath the body
of the regulators.
• Ensure that the decoupling capacitors, especially tantalum, or high capacity ceramic types,
have the requisite low ESR, ESL and good stability/temperature properties. Refer to the
regulator manufacturer’s datasheet for more information.
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Appendix B. Reference Configuration
The values listed below are used in the reference unit to validate the interfaces and derive the
characterization data provided in Section 9. The fields that are not listed have their values set
to 0 (which is replaced by a default value).
See mXT1664S 2v0 Protocol Guide for information about the individual objects and their
fields.
The values for the user’s application will depend on the circumstances of that particular project
and will vary from those listed here. Further tuning will be required to achieve an optimal
performance..
Field
Value
Power Configuration T7 – GEN_POWERCONFIG_T7 (Instance 0)
IDLEACQINT
10
10
10
ACTVACQINT
ACTV2IDLETO
Acquisition Configuration T8 – GEN_ACQUISITIONCONFIG_T8 (Instance 0)
CHRGTIME
TCHDRIFT
DRIFTST
132
20
20
ATCHCALST
255
Multiple Touch Touchscreen T9 – TOUCH_MULTITOUCHSCREEN_T9 (Instance 0)
CTRL
142
XSIZE
32
52
130
80
2
YSIZE
BLEN
TCHTHR
TCHDI
ORIENT
1
MRGTIMEOUT
MOVHYSTI
MOVHYSTN
MOVFILTER
NUMTOUCH
MRGHYST
MRGTHR
AMPHYST
XRANGE
YRANGE
XLOCLIP
10
20
5
48
10
20
20
20
3071
3071
10
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Field
Value
14
XHICLIP
YLOCLIP
13
YHICLIP
8
XEDGECTRL
202
35
XEDGEDIST
YEDGECTRL
140
20
YEDGEDIST
JUMPLIMIT
39
TCHHYST
20
XPITCH
41
YPITCH
44
Self Test T25 – SPT_SELFTEST_T25 (Instance 0)
PINDWELLUS
200
Grip Suppression T40 – PROCI_GRIPSUPPRESSION_T40 (Instance 0)
XLOGRIP
XHIGRIP
YLOGRIP
YHIGRIP
20
20
20
20
Touch Suppression T42 – PROCI_TOUCHSUPPRESSION_T42 (Instance 0)
APPRTHR
32
30
30
127
5
MAXAPPRAREA
MAXTCHAREA
SUPSTRENGTH
SUPDIST
DISTHYST
5
Digitizer HID Configuration T43 – SPT_DIGITIZER_T43 (Instance 0)
CTRL
136
125
224
XLENGTH
YLENGTH
Stylus T47 – PROCI_STYLUS_T47 (Instance 0)
CONTMIN
20
45
5
CONTMAX
STABILITY
MAXTCHAREA
AMPLTHR
3
60
10
2
STYSHAPE
CONFTHR
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Field
Value
32
SYNCSPERX
CFG
15
Stylus T47 – PROCI_STYLUS_T47 (Instance 1)
CFG
80
Adaptive Threshold T55 – PROCI_ADAPTIVETHRESHOLD_T55 (Instance 0)
TARGETTHR
24
40
1
THRADJLIM
RESETSTEPTIME
FORCECHGDIST
SlimSensor T56 – PROCI_SHIELDLESS_T56 (Instance 0)
CTRL
2
3
OPTINT
1
INTTIME
48
21
20
21
21
21
21
21
22
22
22
22
23
22
22
22
22
23
23
23
23
22
23
22
22
INTDELAY[0]
INTDELAY[1]
INTDELAY[2]
INTDELAY[3]
INTDELAY[4]
INTDELAY[5]
INTDELAY[6]
INTDELAY[7]
INTDELAY[8]
INTDELAY[9]
INTDELAY[10]
INTDELAY[11]
INTDELAY[12]
INTDELAY[13]
INTDELAY[14]
INTDELAY[15]
INTDELAY[16]
INTDELAY[17]
INTDELAY[18]
INTDELAY[19]
INTDELAY[20]
INTDELAY[21]
INTDELAY[22]
INTDELAY[23]
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Field
Value
22
22
22
22
21
21
21
21
25
2
INTDELAY[24]
INTDELAY[25]
INTDELAY[26]
INTDELAY[27]
INTDELAY[28]
INTDELAY[29]
INTDELAY[30]
INTDELAY[31]
GCLIMIT
TOUCHBIAS
BASESCALE
9
SHIFTLIMIT
5
maXCharger T62 – PROCG_NOISESUPPRESSION_T62 (Instance 0)
CALCFG1
2
2
CALCFG3
MAXSELFREQ
25
5
HOPCNT
HOPCNTPER
10
5
HOPEVALTO
HOPST
5
NLGAIN
90
45
45
48
15
63
6
MINNLTHR
INCNLTHR
ADCSPERXTHR
NLTHRMARGIN
MAXADCSPERX
ACTVADCSVLDNOD
IDLEADCSVLDNOD
6
MINGCLIMIT
4
MAXGCLIMIT
64
maXStartup T66 – SPT_GOLDENREFERENCES_T66 (Instance 0)
FCALFAILTHR
60
60
FCALDRIFTCNT
CTE_SCAN Configuration T77 – SPT_CTESCANCONFIG_T77 (Instance 0)
CTRL
13
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Field
Value
2
ACTVPRCSSCNEXT
XZOOMGAIN
XZOOMTCHTHR
40
50
80
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Appendix C. Glossary of Terms
Channel
One of the capacitive measurement points at which the sensor controller can detect
capacitive change.
Jitter
The peak-to-peak variance in the reported location for an axis when a fixed touch is
applied. Typically jitter is random in nature and has a Gaussian (1) distribution, therefore
measurement of peak-to-peak jitter must be conducted over some period of time, typically
a few seconds. Jitter is typically measured as a percentage of the axis in question.
For example a 100 x 100 mm touchscreen that shows 0.5% jitter in X and 1% jitter in Y
would show a peak deviation from the average reported coordinate of 0.5 mm in X and
1 mm in Y. Note that by defining the jitter relative to the average reported coordinate, the
effects of linearity are ignored.
Linearity
The measurement of the peak-to-peak deviation of the reported touch coordinate in one
axis relative to the absolute position of touch on that axis. This is often referred to as the
nonlinearity. Non-linearities in either X or Y axes manifest themselves as regions where the
perceived touch motion along that axis (alone) is not reflected correctly in the reported
coordinate giving the sense of moving too fast or too slow. Linearity is measured as a
percentage of the axis in question.
For each axis, a plot of the true coordinate versus the reported coordinate should be a
perfect straight line at 45°. A non-linearity makes this plot deviate from this ideal line. It is
possible to correct modest non-linearities using on-chip linearization tables, but this
correction trades linearity for resolution in regions where stronger corrections are needed
(because there is a stretching or compressing effect to correct the nonlinearity, so altering
the resolution in these regions). Linearity is typically measured using data that has been
sufficiently filtered to remove the effects of jitter. For example, a 100 mm slider with a
nonlinearity of 1% reports a position that is, at most, 1 mm away in either direction from
the true position.
Resolution
The measure of the smallest movement on a slider or touchscreen in an axis that causes a
change in the reported coordinate for that axis. Resolution is normally expressed in bits
and tends to refer to resolution across the whole axis in question. For example, a resolution
of 10 bits can resolve a movement of 0.0977 mm on a slider 100 mm long. Jitter in the
reported position degrades usable resolution.
Touchscreen
A two-dimensional arrangement of electrodes whose capacitance changes when touched,
allowing the location of touch to be computed in both X and Y axes. The output from the XY
computation is a pair of numbers, typically 12-bits each, ranging from 0 to 4095,
representing the extents of the touchscreen active region.
1. Sometimes called Bell-shaped or Normal distribution.
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Appendix D. QMatrix Primer
D.1 Acquisition Technique
QMatrix capacitive acquisition uses a series of pulses to deposit charge into a sampling capacitor,
Cs. The pulses are driven on X lines from the controller. The rising edge of the pulse causes
current to flow in the mutual capacitance, Cx, formed between the X line and a neighboring receiver
electrode or Y line. While one X line is being pulsed, all others are grounded. This leads to excellent
isolation of the particular mutual capacitances being measured (1), a feature that makes for good
inherent touchscreen performance.
After a fixed number of pulses (known as the burst length) the sampling capacitor's voltage is
measured to determine how much charge has accumulated. This charge is directly proportional to
Cx and therefore changes if Cx (2) changes. The transmit-receive charge transfer process between
the X lines and Y lines causes an electric field to form that loops from X to Y. The field itself
emanates from X and terminates on Y. If the X and Y electrodes are fixed directly (3) to a dielectric
material like plastic or glass, then this field tends to channel through the dielectric with very little
leakage of the field out into free-space (that is, above the panel). Some proportion of the field does
escape the surface of the dielectric, however, and so can be influenced during a touch.
When a finger is placed in close proximity (a few millimeters) or directly onto the dielectric's surface,
some of this stray field and some of the field that would otherwise have propagated via the dielectric
and terminated onto the Y electrode, is diverted into the finger and is conducted back to the
controller chip via the human body rather than via the Y line.
This means that less charge is accumulated in Cs, and hence the terminal voltage present on Cs,
after all the charge transfer pulses are complete, becomes less. In this way, the controller can
measure changes in Cx during touch. This means that the measured capacitance Cx goes down
during touch, because the coupled field is partly diverted by the touching object.
The spatial separation between the X and Y electrodes is significant to make the electric field to
propagate well in relation to the thickness of the dielectric panel.
D.2 Moisture Resistance
A useful side effect of the QMatrix acquisition method is that placing a floating conductive element
between the X and Y lines tends to increase the field coupling and so increases the capacitance
Cx. This is the opposite change direction to normal touch, and so can be quite easily ignored or
compensated for by the controller. An example of such floating conductive elements is the water
droplets caused by condensation.
As a result, QMatrix-based touchscreens tend not to go into false detect when they are covered in
small non-coalesced water droplets. Once the droplets start to merge, however, they can become
large enough to bridge the field across to nearby ground return paths (for example, other X lines
not currently driven, or ground paths in mechanical chassis components). When this happens, the
screen's behavior can become erratic.
1. A common problem with other types of capacitive acquisition technique when used for touchscreens, is that this
isolation is not so pronounced. This means that when touching one region of the screen, the capacitive signals also
tend to change slightly in nearby channels too, causing small but often significant errors in the reported touch
position.
2. To a first approximation.
3. Air gaps in front of QMatrix sensors massively reduce this field propagation and kill sensitivity. Normal optically clear
adhesives work well to attach QMatrix touchscreens to their dielectric front panel.
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There are some measures used in these controllers to help with this situation, but in general there
comes a point where the screen is so contaminated by moisture that false detections become
inevitable. It should also be noted that uniform condensation soon becomes non-uniform once a
finger has spread it around. Finger grease renders the water highly conductive, making the situation
worse overall.
In general, QMatrix has industry-leading moisture tolerance but there comes a point when even the
best capacitive touchscreen suffers due to moisture on the dielectric surface.
D.3 Interference Sources
D.3.1
Power Supply
The device can tolerate short-term power supply fluctuations. If the power supply fluctuates
slowly with temperature, the device tracks and compensate for these changes automatically
with only minor changes in sensitivity. If the supply voltage drifts or shifts quickly, the drift
compensation mechanism is not able to keep up, causing sensitivity anomalies or false
detections.
The device itself uses the AVdd power supply as an analog reference, so the power should be
very clean and come from a separate regulator. A standard inexpensive Low Dropout (LDO)
type regulator should be used that is not also used to power other loads, such as LEDs,
relays, or other high current devices. Load shifts on the output of the LDO can cause AVdd to
fluctuate enough to cause false detection or sensitivity shifts. The digital Vdd supply is far
more tolerant to noise.
CAUTION: A regulator IC shared with other logic can result in erratic
operation and is not advised.
Noise on AVdd can appear directly in the measurement results. Vdd should be checked to
ensure that it stays within specification in terms of noise, across a whole range of product
operating conditions.
Ceramic bypass capacitors on AVdd and Vdd, placed very close (<5 mm) to the chip are
recommended. A bulk capacitor of at least 1 µF and a higher frequency capacitor of around
10 nF to 100 nF in parallel are recommended; both must be X7R or X5R dielectric capacitors.
D.3.2
Other Noise Sources
Refer to QTAN0079, Buttons, Sliders and Wheels Sensor Design Guide, for information
(downloadable from the Touch Technology area of the Atmel website).
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Appendix E. I2C Basics (I2C-compatible Operation)
9.19 Interface Bus
The device communicates with the host over an I2C-compatible bus. The following sections
give an overview of the bus; more detailed information is available from www.i2C-bus.org.
Devices are connected to the I2C-compatible bus as shown in Figure E-1. Both bus lines are
connected to Vdd via pull-up resistors. The bus drivers of all I2C-compatible devices must be
open-drain type. This implements a wired AND function that allows any and all devices to drive
the bus, one at a time. A low level on the bus is generated when a device outputs a zero.
Figure E-1. I2C-compatible Interface Bus
Vdd
Device 1
Device 2
Device 3
Device n
R1
R2
SDA
SCL
E.1 Transferring Data Bits
Each data bit transferred on the bus is accompanied by a pulse on the clock line. The level of
the data line must be stable when the clock line is high; the only exception to this rule is for
generating START and STOP conditions.
Figure E-2. Data Transfer
SDA
SCL
Data Stable
Data Stable
Data Change
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E.2 START and STOP Conditions
The host initiates and terminates a data transmission. The transmission is initiated when the
host issues a START condition on the bus, and is terminated when the host issues a STOP
condition. Between the START and STOP conditions, the bus is considered busy. As shown in
Figure E-3, START and STOP conditions are signaled by changing the level of the SDA line
when the SCL line is high.
Figure E-3. START and STOP Conditions
SDA
SCL
START
STOP
E.3 Address Byte Format
All address bytes are 9 bits long, consisting of 7 address bits, one READ/WRITE control bit
and an acknowledge bit. If the READ/WRITE bit is set, a read operation is performed,
otherwise a write operation is performed. When the device recognizes that it is being
addressed, it will acknowledge by pulling SDA low in the ninth SCL (ACK) cycle. An address
byte consisting of a slave address and a READ or a WRITE bit is called SLA+R or SLA+W,
respectively.
The most significant bit of the address byte is transmitted first. The address sent by the host
must be consistent with that selected with the option jumpers.
Figure E-4. Address Byte Format
Addr MSB
Addr LSB
ACK
R/W
SDA
SCL
1
2
7
8
9
START
E.4 Data Byte Format
All data bytes are 9 bits long, consisting of 8 data bits and an acknowledge bit. During a data
transfer, the host generates the clock and the START and STOP conditions, while the receiver
is responsible for acknowledging the reception. An acknowledge (ACK) is signaled by the
receiver pulling the SDA line low during the ninth SCL cycle. If the receiver leaves the SDA
line high, a NACK is signaled.
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Figure E-5. Data Byte Format
Data LSB
Data MSB
ACK
Aggregate
SDA
SDA from
Transmitter
SDA from
Receiver
SCL from
Master
1
2
7
8
9
SLA+R/W
Data Byte
Stop or Next
Data Byte
E.5 Combining Address and Data Bytes into a Transmission
A transmission consists of a START condition, an SLA+R/W, one or more data bytes and a
STOP condition. The wired “ANDing” of the SCL line is used to implement handshaking
between the host and the device. The device extends the SCL low period by pulling the SCL
line low whenever it needs extra time for processing between the data transmissions.
Note: Each write or read cycle must end with a stop condition. The device may not respond
correctly if a cycle is terminated by a new start condition.
Figure E-6 shows a typical data transmission. Note that several data bytes can be transmitted
between the SLA+R/W and the STOP.
Figure E-6. Byte Transmission
Addr MSB
Addr LSB
Data MSB
Data LSB
ACK
ACK
R/W
SDA
SCL
1
2
7
8
9
1
2
7
8
9
START
SLA+RW
Data Byte
STOP
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Table of Contents
Features ................................................................................................. 1
Overview of the mXT1664S1 ............................................................... 3
1
2
3
1.1
1.2
1.3
Introduction ...................................................................................................3
Understanding Unfamiliar Concepts ..............................................................3
Resources .....................................................................................................4
Pinout and Schematic .......................................................................... 5
2.1
2.2
2.3
Pinout Configuration ......................................................................................5
Pinout Descriptions .......................................................................................6
Schematics ..................................................................................................11
Touchscreen Basics .......................................................................... 14
3.1
3.2
3.3
3.4
Sensor Construction ....................................................................................14
Electrode Configuration ...............................................................................14
Scanning Sequence ....................................................................................15
Touchscreen Sensitivity ..............................................................................15
4
Detailed Operation ............................................................................. 16
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
Power-up/Reset ..........................................................................................16
Calibration ...................................................................................................18
Operational Modes ......................................................................................18
Touchscreen Layout ....................................................................................18
Signal Processing .......................................................................................19
Circuit Components .....................................................................................22
PCB Layout .................................................................................................23
Debugging ...................................................................................................23
Communications .........................................................................................23
Configuring the Device ................................................................................24
5
I2C-compatible Communications ..................................................... 25
5.1
5.2
5.3
5.4
5.5
5.6
5.7
Communications Protocol ...........................................................................25
I2C-compatible Addresses ..........................................................................25
Writing To the Device ..................................................................................25
I2C-compatible Writes in Checksum Mode ..................................................26
Reading From the Device ...........................................................................26
Reading Status Messages with DMA ..........................................................27
CHG Line ....................................................................................................29
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5.8
5.9
SDA, SCL ....................................................................................................31
Clock Stretching ..........................................................................................31
6
USB Communications ........................................................................ 32
6.1
6.2
6.3
6.4
6.5
6.6
Communications Protocol ...........................................................................32
Endpoint Addresses ....................................................................................32
Composite Device .......................................................................................33
Interface 0 (Digitizer HID) ............................................................................33
Interface 1 (Generic HID) ............................................................................37
USB Suspend Mode ....................................................................................44
7
HID-I2C-compatible Communications .............................................. 45
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
Communications Protocol ...........................................................................45
I2C-compatible Addresses ...........................................................................45
Device .........................................................................................................45
Interface 0 (Digitizer HID-I2C) ......................................................................45
Interface 1 (Generic HID-I2C) ......................................................................49
CHG Line ....................................................................................................53
SDA, SCL ....................................................................................................54
Clock Stretching ..........................................................................................54
Power Control .............................................................................................54
Microsoft Windows 8 Compliance ...............................................................54
8
9
Getting Started with mXT1664S1 ...................................................... 55
8.1
8.2
8.3
8.4
8.5
Establishing Contact ...................................................................................55
Using the Object Protocol ...........................................................................55
Writing to the Device ...................................................................................55
Reading from the Device .............................................................................56
Configuring the Device ................................................................................56
Specifications ..................................................................................... 58
9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
Absolute Maximum Specifications ...............................................................58
Recommended Operating Conditions .........................................................58
DC Characteristics ......................................................................................58
ESD Information ..........................................................................................59
Supply Current ............................................................................................60
Current Consumption ..................................................................................62
Timing Specifications ..................................................................................66
I2C-compatible Specifications .....................................................................67
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9.9
USB Specification .......................................................................................67
HID-I2C Specification ..................................................................................68
Touch Accuracy and Repeatability ..............................................................68
Power Supply and Ripple Noise ..................................................................68
Thermal Packaging .....................................................................................68
Soldering Profile ..........................................................................................69
Mechanical Dimensions ..............................................................................70
Part Marking ................................................................................................71
Part Numbers ..............................................................................................71
Silicon Revision Identification ......................................................................71
Moisture Sensitivity Level (MSL) .................................................................71
9.10
9.11
9.12
9.13
9.14
9.15
9.16
9.17
9.18
9.19
Appendix A
PCB Design Considerations ........................................ 72
Introduction .................................................................................................72
Printed Circuit Board ...................................................................................72
Supply Rails and Ground Tracking ..............................................................72
Power Supply Decoupling ...........................................................................72
Suggested Voltage Regulator Manufacturers .............................................73
Crystal Oscillator .........................................................................................74
Analog I/O ...................................................................................................74
Component Placement ................................................................................75
Digital Signals .............................................................................................75
EMC and Other Observations .....................................................................75
A.1
A.2
A.3
A.4
A.5
A.6
A.7
A.8
A.9
A.10
Appendix B
Appendix C
Reference Configuration .............................................. 76
Glossary of Terms ........................................................ 81
Appendix D
QMatrix Primer .............................................................. 82
Acquisition Technique .................................................................................82
Moisture Resistance ....................................................................................82
Interference Sources ...................................................................................83
D.1
D.2
D.3
Appendix E
I2C Basics (I2C-compatible Operation) ...................... 84
Interface Bus ...............................................................................................84
Transferring Data Bits .................................................................................84
START and STOP Conditions .....................................................................85
Address Byte Format ..................................................................................85
Data Byte Format ........................................................................................85
9.20
E.1
E.2
E.3
E.4
89
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E.5
Combining Address and Data Bytes into a Transmission ...........................86
Table of Contents................................................................................ 87
Revision History.................................................................................. 91
90
mXT1664S1
9871EX–AT42–12/13
mXT1664S1
Revision History
Revision Number
History
Revision AX – April 2013
Revision BX – April 2013
Revision CX – June 2013
Revision DX – October 2013
Revision EX – December 2013
Initial release for firmware revision 2.0
Corrected the part number
Updated Vdd specifications
Corrected the QSS number
Added CU parts to part numbers
91
9871EX–AT42–12/13
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