Touch

The board is equipped with four QTouch keys. The QTouch functionality is handled by an Atmel QTouch device, AT42QT1040. Keys are included in the PCB itself (CS[3:0]). By default, the QTouch device is configured in ASK mode (Adjacent Key Suppression) so key combinations are not possible.

An AT42QT1040 output pin goes active low when the corresponding key is touched. Because outputs are open-drain type, it is necessary to activate the internal pull-up resistors of PORTE (PE[7:4]) as soon as possible in the application firmware.

Note:

Adding top modules to the board with functionality connected to these pins is not recommended. But if no key is touched, the module functionality will run correctly.
The QTouch device is very close to the keys. The sensitivity of the sensor lines of the device is very high on its exposed pins, and so touching its I/O pins will give erroneous result in the touch sensing mechanism