node-red-node-pi-gpio: Support for GPIO.BCM mode in nrpio.py

Hi,

we started working on some automation tasks with node-red on a industrial raspi. For setting a GPIO output with the pi-gpio node I encounter the problem, that the mode GPIO.BOARD is not supported with raspi compute module.

Running the python script manually I get the following error:

Traceback (most recent call last):
  File "./nrgpio.py", line 34, in <module>
    GPIO.setmode(GPIO.BOARD)
RuntimeError: BOARD numbering system not applicable on compute module

Could you please add the option to let the user choose either GPIO.BOARD or GPIO.BCM as mode.

Changing the mode manually in the script works like a charm.

Thanks,
Tobias

Start by inspecting nrpio.py and the nrgpio.py entry point shown in the traceback, then trace how the pi-gpio node selects its GPIO mode. The work is done when users can choose GPIO.BOARD or GPIO.BCM and the selected mode works on the relevant Raspberry Pi hardware; no test file is mentioned in the issue.