GPIO pins - how do they work

Noob warning! :slight_smile:

How does the 14pin UART/I2C/SPI/GPIO work?
Can I get dome GPIO board/pins and hooked them to the GameShell, is that it?


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Well we will need to have the hardware to be able to answer that.

Some of them will probably be available using /sys/*/gpio interface, hard to say right now to be honest

I messaged Clockwork about this during the campaign. What I was told is that the GameShell would come with a manual detailing the specs of the cable that comes with it for that port and what the pins can be used for. As @Godzil said, we need to wait for the device to be shipped to us to know the specifics on this.

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Or for clockwork to give more documentation before the hardware release


Supposedly it’s online somewhere / will be online at some point.

At least they will provide a cable which is good!

I’m trying to control the pins through /sys/class/gpio

for any pin N, I get

cpi@clockworkpi:~$ cd /sys/class/gpio
cpi@clockworkpi:/sys/class/gpio$ su root
root@clockworkpi:/sys/class/gpio# ls
export  gpiochip0  gpiochip352  unexport
root@clockworkpi:/sys/class/gpio# echo N > export
root@clockworkpi:/sys/class/gpio# ls
export  gpioN  gpiochip0  gpiochip352  unexport
root@clockworkpi:/sys/class/gpio# cat gpioN/direction
root@clockworkpi:/sys/class/gpio# echo out > gpioN/direction
bash: echo: write error: Unknown error 517

Sadly I get that error when I try to set pins to output mode. It may be possible to read the values of the pins. But how are the pins numbered? Looking at the mainboard schematic I believe our gpio diagram is the part called “debug.” I probed the gpios with a multimeter and the 3 and 5 volt levels correspond to the diagram. I don’t dare short two pins together to test if it’s reflected in cat gpioN/value.

What’s the next step in unlocking the secrets of clockwork pi gpio?

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search Debug UART

and here is the order in reality
reference picture


from left to right is

blue green yellow white
1, 2, 3, 4…

in above Mainboard Schematic Layout

so if you want a usb-uart connector, just leave the blue alone and connect the
green(rx) yellow(tx) ,white(GND) and it will be done

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GPIO should be here. But Gods know how PIN match the wire color.


You can map those pin to Allwinner R16 spec page 18

Note that they claim this is open source hardware. But the info on the hardware is not fully public. I will wait till they open all and see their limitation before click the pay button.

of course it’s opensource

READ the github documents

I think you are looking for the clockwork_Mainboard_Schematic.pdf

the gpio in back 14 pins is in the DEBUG section of the schematic pdf