Toradex Colibri - Touch Panel Interface; Resistive Touch Signals; Reference Schematics; Unused Touch Panel Interface Signal Termination

Colibri Carrier Board Design Guide
Toradex AG l Altsagenstrasse 5 l 6048 Horw l Switzerland l +41 41 500 48 00 l www.toradex.com l info@toradex.com
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2.15 Touch Panel Interface
The Colibri module standard features a touch panel interface for resistive touch screens. This
allows integrating a touch screen solution with a minimum amount of components on the carrier
board. This standard supports four-wire resistive touch screens. Some modules also support five-
wire touch. Read the corresponding datasheet of the module for more information.
2.15.1 Resistive Touch Signals
Colibri
Pin
Colibri
Signal Name
I/O
Type
Power
Rail
Description
14
TOUCH_4-wire_PX
I/O
Analog
3.3V
X+ (4-wire)
16
TOUCH_4-wire_MX
I/O
Analog
3.3V
X- (4-wire)
18
TOUCH_4-wire_PY
I/O
Analog
3.3V
Y+ (4-wire)
20
TOUCH_4-wire_MY
I/O
Analog
3.3V
Y- (4-wire)
Table 21: Digital Audio Signals
2.15.2 Reference Schematics
To reduce the noise that is picked up by the display or long cables, it is recommended to add
capacitors to the touch screen signals. 1nF to 10nF is a good choice. It is also recommended to
add clamping diodes to protect the input of the touch screen controller against ESD.
Figure 25: Touch Interface Reference Schematic
2.15.3 Unused Touch Panel Interface Signal Termination
Unused touch panel signals can be left unconnected or pull down the signals individually with
10kΩ resistors. It is recommended to disable the corresponding drivers.
GND
1nF
50V
C103
1nF
50V
C100
1nF
50V
C101
1nF
50V
C102
TSW-103- 07- G-D
1
2
3
4
5
6
X16
2.54mm Male
AN1_TSPX
AN1_TSMX
AN1_TSPY
AN1_TSMY
AN1_TSPX
AN1_TSMX
AN1_TSPY
AN1_TSMY
RCLAMP050 4S
1
2
34
5
6
D8
GND
147300 5-1
PIN_14 / TOUCH_TSPX
14
PIN_16 / TOUCH_TSMX
16
PIN_18 / TOUCH_TSPY
18
PIN_20 / TOUCH_TSMY
20
Colibri -Touch
9 of 16
X1I