[SOLVED] some GPIO pins do not produce any output.
I have made a shield for an Up squared and started testing it, but ran into problems with configuring some pins as outputs.
I have a UP² with N4200, 4GB RAM and 32GB eMMC, run Linux (had a flavor of Debian, but put now Ubuntu 18.04 on it), and have BIOS 3.3 on it.
I am able to set some pins as outputs (e.g. 16 and 18 (linux pins 471 and 405)) and steer a led with it. For this I used the example of the UP2 pinout page: https://wiki.up-community.org/Pinout_UP2. However some I can configure as output, but the pin output does not change.
Thinking it might be my shield, I repeated the test with another board, the UP² with E3940, 4GB and 32GB eMMC, on which I never put a shield, but I still have problems in setting outputs (in my case pin 13 and 15 (432 & 431).
I tested all pins and came with the following result:
Physical pins of which I can set the output and work perfect: 8, 11, 12, 16, 18, 22, 23, 24, 26, 29, 32, 33, 40 (Linux gpio 477, 478, 326, 471, 405, 402, 419, 420, 430, 468, 469, 329)
Physical pins of which I cannot toggle the output (but I do not get any error, while setting it up): 7, 10(UART_RX), 13, 15, 31, 37, 38(AVS_I2S6_SDI) (Linux gpio 433,476, 432, 431, 404, 403, 328)
Physical pins that are always 3V3: 3, 5, 27, 28 (all I2C) (Linux gpio 462, 463, 464, 465)
Physical pins that are always 0V: 19 (SPI MOSI) (linux gpio 422)
I can understand that some pins maybe cannot work because of their function (I2C, UART_RX), but some pins that are only gpio, should work as output, right?
I already searched the community and couldn’t find anything.
Since the problem occurs on multiple pins, there might be a very simple cause (and hopefully very simple solution).
I hope you can help me!