Device Trees and Overlays

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1

Hi there

I want to change some multiplexer settings for the gpio to enable some interfaces for the sitara processor.

I decompiled the am335-boneblack.dtb and made some modifications. (is this the way to do it, or is it easier to use the default dtsi files and compile a new device tree ? )
For the UART and I2C this is not a problem and i figured out how to control the pins etc.

But i do not manage to change the given source file to enable the ehrpwm1a/2a/2b.
Can anyone help me out here?

In the internet there are a lot of examples using a device tree overlay, but since i will not use the beaglebone itself in the future (and the capemanager folder is anyway somehow not available) i want to have all the changes in one dtb file.

Is there a way to load device tree overlays without the capemanger via uEnv.txt?
(Still the one file solution would be prefered)

Thanks a lot in advance.

Best regards,
Patrick

2

each pwm actually has two nodes you need to enable, look at this
overlay for hints:

epwmss0/ehrpwm0

https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-PWM0-00A0.dts

(the pinmux-helper isn't needed)

Regards,

3

I added this to my uEnv.txt to select which device-tree overlays should be enabled and disabled at boot time:

optargs=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN capemgr.enable_partno=EBB-PRU-Example,BB-ADC,bone_pwm_P8_34,am33xx_pwm,

Warning: There seems to be a limit on how many DTOs can go in the “enable” list. If I put additional DTOs in, they don’t get loaded for some reason.

Is that what you’re looking for?

Best,
-Justin