GPIO based LEDs with USR LED functions

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1

i really thought i would find this online someplace but,
can i use the trigger and heartbeat type functions on a LED connected to GPIO on my custom board based on the BBB design?
this would save me time in my code that is already quite busy.
i noticed some example from 3.14 kernel days
i’m 4.4.62 and ubuntu 16.04
and controlling them from c code.

thanks so much,
Michael

2

Can you ask a more specific question ? It seems as though as you;re asking if you can use the sysfs file system to control USR0-USR3 ?

The answer is yes, you can, but it largely depends on which drivers you’re loading with your hardware. Using /dev/mem/ + mmap all you need to know if the memory map for the GPIO pins. But for sysfs access, you need to load certain drivers at boot.

3

excellent, thanks.
this is my first exposure to overlays etc… now i see about sysfs.
i’ll just blink leds in my code. using threads won’t suck up hardly any processor time.
ciao,

4

OK so assuming you have everything loaded as per the normal Debian image . . .
root@wgd:~# ls /sys/class/leds/
beaglebone:green:usr0 beaglebone:green:usr1 beaglebone:green:usr2 beaglebone:green:usr3

This is the path you’re looking for then:
root@wgd:~# ls /sys/class/leds/beaglebone:green:usr0
brightness device invert max_brightness power subsystem trigger uevent

You can work with individual led files from there. Which I do not remember how closely this matched to earlier kernels . . . It’s been a long time for me since I’ve worked with anything but kernel 4.x . . .