GPIO on UP²
I use an UP² with kernel 5.4 and Ubuntu 18.04 installed just as described on the official wiki page. The rules to add in /lib/udev/... have also been installed.
I tried first to blink a led using pin 13 (Linux GPIO 432) and Sysfs as described on the wiki page without any success. I then had a look in the BIOS and saw in Advanced > HAT Configurations that none of the pin was tagged "GPIO". So I changed the ones I can to "GPIO" (which basically means I changed 8 pins: PWM and some others). Then I tried again to blink my led but using the pin 16 (471, PWM3 now parametrized as a GPIO in the BIOS) without any success neither...
I finally managed to make my led blink by switching back to the initial configuration in the BIOS and using either one of the 3 PWM pins. I also tried the mraa library and got an issue: mraa-list returns "No pins". However I am still able to use the python bindings provided I set raw to True and use the Linus GPIO numbers.
So here are my conclusions/questions:
1) It seems that only the pins with a given function can be used and that I need to keep the function as "PWM" even if I use it as a generic output. Am I right?
2) Is there any way to use the other pins as true GPIO? Looking at the datasheet I thought it was possible but now I am not so sure...
3) I guess I should be able to use mraa library with mraa numbering, isn't it? So any clue why my mraa-list is empty?
Thanks a lot for your help