ETRA SBC/Interfaces and Connectors/Touchscreen

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Version Issue Date Notes
1.0.0 Dec 2020 First Release


Touchscreen interface[edit | edit source]

Description[edit | edit source]

The Touchscreen interface is available on the Evaluation Kit at the connector J20

J20 is a 6 pin Molex PicoBlade connector for the I2C and control signals needed by most of the capacitive TSC.

This interface can be configured to work with 3.3V (default) or 5V power and signal levels.


Signals[edit | edit source]

The following table describes the interface signals:

Pin# SOM Pin# Pin name Pin function Pin Notes
1 - DGND Ground
2 J18.48 TOUCH_SDA I2C_SDA
3 J18.38 TOUCH_SCL I2C_SCL
4 J18.101 TOUCH_VDD TSC power powered through a control switch
5 J18.201 TOUCH_INT TSC interrupt input
6 J18.199 TOUCH_RES TSC reset output

Device mapping[edit | edit source]

The device is typically mapped to /dev/touchscreen0 device in Linux.

The touch controller is attached to the generic Linux input event interface (evdev).

Device usage[edit | edit source]

The simplest tools for touch screen management are the tslib library and ts_tools utilities. To calibrate the touch screen, the ts_calibrate command line tool is available. After calibration, the touch screen can be tested using the graphical ts_test utility or the ts_print command line tool.