I have a problem with GPIO in Adafruit Python IO library on Debian (from armhf.org). It works as root, but not as regular user.
I've added udev rule;
KERNEL=="gpio*", SUBSYSTEM=="gpio", ACTION=="add", PROGRAM="/bin/sh -c 'chown -R debian:gpio /sys/class/gpio'"
KERNEL=="gpio*", SUBSYSTEM=="gpio", ACTION=="add", PROGRAM="/bin/sh -c 'chown -R debian:gpio /sys/devices/virtual/gpio/'"
My user "debian" is in group "gpio". Now I can control gpio using echo... > /sys... in user's shell. But not with python. It just does not work without errors.
However, if I run manually "echo 45 > /sys/class/gpio/export" and then start python on this gpio it will work.
I can see gpio45 in /sys/class/gpio after starting the python script, but it does not work.It will only work after manual export. I tried to compile function gpio_export() from source code and start it manually. It actually works. But in real script it only creates gpio file and doesn't work.
Here is my test script:
import Adafruit_BBIO.GPIO as GPIO
import time
P = "P8_11"
GPIO.setup(P, GPIO.OUT)
for i in xrange(100):
if i % 2 == 0:
GPIO.output(P, GPIO.HIGH)
else:
GPIO.output(P, GPIO.LOW)
time.sleep(0.5)
GPIO.cleanup()
Thanks
-=UPDATED=- It's a bug. I posted it on project's github page along with brutal patch which solves the problem for me https://github.com/adafruit/adafruit-beaglebone-io-python/issues/36
--- adafruit-beaglebone-io-python/source/py_gpio.c 2013-09-17 20:10:08.000000000 +0300
+++ adafruit-beaglebone-io-python/source/py_gpio.c 2013-09-21 02:54:43.000000000 +0300
@@ -105,10 +105,26 @@
if (get_gpio_number(channel, &gpio))
return NULL;
-
- gpio_export(gpio);
- gpio_set_direction(gpio, direction);
- gpio_set_value(gpio, pud);
+
+ unsigned int count = 1000000;
+ int res = -1;
+ do {
+ res = gpio_export(gpio);
+ } while(res != 0 && count-- > 0);
+ if(count == 0)
+ return NULL;
+ count = 1000000;
+ do {
+ res = gpio_set_direction(gpio, direction);
+ } while(res != 0 && count-- > 0);
+ if(count == 0)
+ return NULL;
+ count = 1000000;
+ do {
+ res = gpio_set_value(gpio, pud);
+ } while(res != 0 && count-- > 0);
+ if(count == 0)
+ return NULL;
gpio_direction[gpio] = direction;
Basically, you have to check return values. In my case open() cannot open newly created by exporting gpio file because it's not yet appeared on a filesystem.
