On Monday, 3 December 2018 08:35:22 UTC+2, Ken Shirriff wrote:
>
> libgpiod looks like a nice API. I tried it out, but I'm rather baffled by
> the behavior. If I try to set a pin with gpioset, it turns the pin off and
> unexports it.
>
> $ config-pin P8_44 1 # This turns P8_44 on as expected
> $ gpioset gpiochip2 9=1 # Should turn on gpio2[9], i.e. P8_44, but turns
> it off.
> $ config-pin P8_44 1# Now config-pin can't access the pin???
> WARNING: GPIO pin not exported, cannot set direction or value!
>
> So why does gpioset turn the pin off instead of on? This isn't specific to
> P8_44; for instance "gpioset gpiochip2 7=1" will mess up P8_46 (gpio2[7]).
> This also happens even if I don't use config-pin, so it's not config-pin
> messing things up.
>
I'm also having problems with libgpiod - it simply does not work on a BBB
with kernel 4.14.71-ti-r80. Cape universal is disabled, relevant pins are
not exported via sysfs gpio interface.
Example: I'm trying to set P9.23 a.k.a. gpio number 49 (gpiochip 1, pin 17)
and absolutely nothing happens. The pin stays in some high-z state,
measuring 0.6 volts:
$ sudo gpioset gpiochip1 17=0
$ sudo gpioset gpiochip1 17=1
Running "gpioinfo gpiochip1" shows my pin as output, while it's definitely
not that:
...
line 17: "GPMC_A1" unused output active-high
...
Also tried to control each of the user LEDs on pins 21-24 on the same port
with very strange results. I managed to switch on usr1 or usr2 and no
further changes are possible - the one LED won't turn off and the others
won't turn on. Also wrote a small C program which uses the "linux/gpio.h"
API - doesn't do anything useful to any of the pins.
Am I missing something here?
--
Kind regars,
Tarmo
--
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