LED devices don't have delay_on/delay_off properties

[ensonic]

The code in https://github.com/topikachu/python-ev3/blob/master/ev3/ev3dev.py#L464-465 exposes delay_on/off properties for the timing. Allthough:

ll /sys/class/leds/ev3-left0:red:ev3dev/
total 0
-rw-rw-r-- 1 root ev3dev 4096 Jul 21 15:15 brightness
lrwxrwxrwx 1 root root      0 Jan  1  2000 device -> ../../../leds_pwm
-r--r--r-- 1 root ev3dev 4096 Jan  1  2000 max_brightness
drwxr-xr-x 2 root root      0 Jan  1  2000 power
lrwxrwxrwx 1 root root      0 Jan  1  2000 subsystem -> ../../../../../class/leds
-rw-rw-r-- 1 root ev3dev 4096 Jul 21 15:15 trigger
-rw-rw-r-- 1 root ev3dev 4096 Jan  1  2000 uevent

[dlech]

You have to set trigger to timer in order to create the delay_on and delay_off attributes in sysfs. This has some unfortunate side effects. See ev3dev/ev3dev#225 for more information.

My advice would be to implement your own blinking function rather than relying on the timer trigger.

[topikachu]

@dlech Is https://github.com/ev3dev/ev3dev/wiki/Using-the-LEDs out of date? It still has delay_on/off

[dlech]

The leds class is part of the mainline linux kernel, so it has not changed and is not likely to. You can use the timer trigger. I just don't recommend it because of permissions and race condition issues with the dynamic sysfs attributes (delay_on/delay_off).

[dlech]

I suppose we should add a link to the issue I mentioned above to that page though.