GPIO pin 12
Is GPIO pin 12 reserved (and thus unavailable) on the Onion's expansion dock? I've tried to write to it with the Console's GPIO tool as well as via terminal using fast-gpio commands. In each case, it appears that this pin is a dedicated output stuck at a LOW logic level (similar to GPIO being an output stuck at HIGH logic level, owing to it's wired connection to the Onion's power-on indicator LED).
For what it's worth, the GPIO pins act the same way with the Mini Dock. I should have mentioned in the original post that it is GPIO pin 8 that is hard-wired to the power-on LED.
By my reckoning, this leaves 10 GPIO pins available for use: 0, 1, 6, 7, 13, 14, 18, 19, 23, and 26. Any comments?
@Jeff-Verive From my understanding, the following is the set of usable GPIO pin numbers:
0, 1, 6, 7, 8, 12, 13, 14, 15, 16, 17, 18, 19, 23, 26 (though I am open to correction on this).
And also my understanding is (as you point out) that pin 8 is output only and used for the LED
I've been meaning to look into why pin 8 is wacky.
@Lazar-Demin Thanks for the clarification.
While I had no additional confirmation, I had assumed pin 8 was the LED because there is a directory gpio8 in /sys/class/gpio and any attempt to perform echo 8 > /sys/class/gpio/export fails while the similar works for other pins. I also noted that there is no direction entry in /sys/class/gpio/gpio8. Additionally, any attempt to use echo 8 > /sys/class/gpio/unexport also fails
Sorry - the list of usable pins was supposed to read "0, 1, 6, 7, 13, 14, 18, 19, 23, 26". These are also the only pins clickable in the Console's GPIO Tool, along with pins 8 and 9, which while clickable they resort to Direction: Output and - respectively - Value: 1 and Value 0. Are schematics for these modules available anywhere for the community? These would help immensely!