On 05.09.18 11:00, Volker Kuhlmann wrote:
> On Wed 05 Sep 2018 19:42:18 NZST +1200, Alexander Graf wrote:
>
>> You need to first make sure the pin is muxed properly as GPIO and not
>> associated with a special function:
>>
>> /sys/kernel/debug/pinctrl/3f200000.gpio/pinmux-pins
>>
>> Once that's clear, you can use the GPIO export to actually access the
>> GPIO function.
>
> Ahh, how obvious... ;-) Thanks! OK, makes sense.
> grep gpio4 pinmux-pins says
> pin 4 (gpio4): (MUX UNCLAIMED) (GPIO UNCLAIMED)
> and I guess it ought to not say "MUX UNCLAIMED".
>
> But I can't find how to do that. All online instructions go straight to
> exporting the pin (assuming a base of 0...).
>
> Appending
> [all]
> gpio=4=op,dh
> gpio=462=op,dh
> to /boot/efi/extraconfig.txt and rebooting makes no difference.
>
> I'm stuck again :-(
Looks like the pin muxing actually happens automatically :)
rpi:~ # grep 'pin 4 ' /sys/kernel/debug/pinctrl/3f200000.gpio/pins
pin 4 (gpio4) function gpio_in in hi; irq 83 (none)
rpi:~ # echo $(( 458 + 4 )) > /sys/class/gpio/export
rpi:~ # echo out > /sys/class/gpio/gpio462/direction
rpi:~ # grep 'pin 4 ' /sys/kernel/debug/pinctrl/3f200000.gpio/pins
pin 4 (gpio4) function gpio_out in lo; irq 83 (none)
rpi:~ # echo 1 > /sys/class/gpio/gpio462/value
rpi:~ # grep 'pin 4 ' /sys/kernel/debug/pinctrl/3f200000.gpio/pins
pin 4 (gpio4) function gpio_out in hi; irq 83 (none)
Alex
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