I had this issue couple times when on boot i2c interface changes group to root automatically (with date 01/01/1970), not sure what is the cause of this problem but it goes out after rebooting. This causes IOError: [Errno 13] Permission denied
when I try to use it with python as it is not in i2c group. Has anybody seen it before and knows how to prevent it happening again?
$ ls -l /dev/i2c*
crw------- 1 root root 89, 0 Jan 1 1970 /dev/i2c-0
crw-rw---- 1 root i2c 89, 1 Sep 1 08:37 /dev/i2c-1
crw-rw---- 1 root i2c 89, 10 Sep 1 08:37 /dev/i2c-10
crw-rw---- 1 root i2c 89, 11 Sep 1 08:37 /dev/i2c-11
crw-rw---- 1 root i2c 89, 12 Sep 1 08:37 /dev/i2c-12
crw------- 1 root root 89, 2 Jan 1 1970 /dev/i2c-2
crw------- 1 root root 89, 3 Jan 1 1970 /dev/i2c-3
crw-rw---- 1 root i2c 89, 4 Sep 1 08:37 /dev/i2c-4
crw------- 1 root root 89, 5 Jan 1 1970 /dev/i2c-5
crw------- 1 root root 89, 6 Jan 1 1970 /dev/i2c-6
crw-rw---- 1 root i2c 89, 7 Sep 1 08:37 /dev/i2c-7
crw------- 1 root root 89, 8 Jan 1 1970 /dev/i2c-8
crw------- 1 root root 89, 9 Jan 1 1970 /dev/i2c-9