The navigation switch is connected to the AVR analog port A7. This port is not present on a standard Arduino, so does not affect normal sketch operation.
When operated, the switch forms a potential divider from the output of the LiPo charger, as shown in the following table:
|Navigation Switch||Ardhat Port A7|
|Open||5V (= 1024) or LiPo voltage when running on battery|
|Left||2⁄3 open circuit voltage|
|Right||1⁄3 open circuit voltage|
As an example, the default factory firmware uses the Nav switch to toggle power to the host, eg Raspberry Pi. You can this use as a starting point for your own applications using the source code on the Ardhat Github repo.
The factory firmware image can easily be expanded to include additional functions, for example sending message to the Pi over the Firmata interface.