How to access GPIOC_7 (pin22, number 475)?

#1

Hi,

Can we use the GPIOC_7 pin 22 in zero?

My hat use this pin for Datacontrol but it’s not working.
If I set the pin HIGH after an export :
echo 1 > /sys/class/gpio/gpio475/value
the value stay still LOW. I’v tested on several zero SBC

The zero documentation says :
Pin#22 (GPIOC_7) and Pin#36 (GPIOH_8) are not available in the user space
However, is it possible to expose and change this GPIO by another way? Libmraa for example?

I wonder because I tell myself, why does this GPIO pin exist if we can’t change the value?

Thanks

#2

I don’t know who wrote that line but if you check the reference manual those 2 pins are open drain (OD), which means they need to have a pull up resistor to work as output, and that was not implemented on our board. I think you can try set them in input mode and check you indeed have access of them from userland. GPIOC_7 is OD3.3V and GPIOH_8 is OD5V, so you should get 0 when connect to GND and 1 when connect to VCC.

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#3

This line was from here : https://wiki.radxa.com/Zero/hardware/gpio

Thank you for your quick reply, it’s much clearer now.

I take this opportunity to say that the zero is a fantastic SBC :slight_smile:
I hope the SBC will be easier to buy soon

#4

I mean I saw the document but it made no sense to me so I was legit wondering who wrote it :rofl:

We should clear the production issue on Zero soon then we can resume selling it.

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