Changes
The GPIO framework and GPIO sysfs interface are documented in
https://www.kernel.org/doc/Documentation/gpio/gpio.txt
===I can see an additional COM port in the device manager, where is it physically?===
*fitlet2 comes with a single RS232 ultra-mini com port.
*There is another COM ports inside the chassis for the use of developing additional FACET cards.
*That additional COM port is no accessible externally whatsoever.
==Software==