Device Trees and Overlays

[Patrick Schmelzer]

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

[Robert Nelson]

On Fri, Dec 23, 2016 at 9:08 AM, Patrick Schmelzer
<patrickrein...@gmail.com> wrote:
> 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.

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,

--
Robert Nelson
https://rcn-ee.com/

[Justin Pearson]

On Friday, December 23, 2016 at 7:08:01 AM UTC-8, Patrick Schmelzer wrote:

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

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