I am not very practical with overlays, so I always go back to editing the original Device Tree file.
You can see from here that those LEDs are connected to GPIOs 85, 86, 87, 88 ( I believe there is a typo in the file wrt the first one).
You need to edit the dtb file in /boot/uboot/dtbs/am335x-boneblack.dtb
so that:
a) it disables the system triggers currently associated with these pins (they show memory, disk and CPU usage, and
b) sets the last one as an input with pulldown, so that it cannot be triggered by Bela's PRU code.
In practice you can just replace your file /boot/uboot/dtbs/am335x-boneblack.dtb
with the one I prepared here.
To do so, you should be able to access the /boot/uboot
partition from your host computer, as the device that shows up as BELABOOT is mounted at that position.
So, navigate to [BELABOOT]/dtbs
, make a copy on your computer of the existing file and replace it with the one I attached, then reboot the board.
CAVEATS:
- if something goes wrong, the board will not boot. If that is the case, replace the file with the copy you made (so make sure you make it in the first place).
- a much better approach is to have a device tree overlay that is loaded after the boot is completed, so you will still get visual feedback from the LEDs during boot.
- if you have a beaglebone green, rename the file to am335x-bonegreen.dtb
- you will get a warning when starting the Bela program. This is nothing to worry about, but you can get rid of it by removing lines
260 led_set_trigger(3, "none");
...
292 led_set_trigger(3, "mmc1");
from core/PRU.cpp
.
If you want to learn more about the topic (recommended), see here.