Linux/PROCESSOR-SDK-AM335X: Library for am335x peripherals

davidino brunelli

Tool/software: Linux

Goodmorning,

I'm using a Beaglebone black and I'm trying to enable PWM at a certain frequency, count the pulses and when a certain number is reached, turn off PWM.

Looking at I didn't find anything so complex.. How can I do it?

More in general, is there a library that can help for all the peripherals?

over 6 years ago

0 davidino brunelli over 6 years ago

Prodigy 190 points

Searching in the net I found, some methods used here: github.com/.../pwmss.c, but I don' t know neither where to find the library nor if there is any documentation about it..
Thank you

0 Pavel Botev over 6 years ago in reply to davidino brunelli

TI__Guru**** 170625 points

Hi Davidino,

In the e2e forum we support only Arago Linux. This linux is coming with the TI PSDK:

software-dl.ti.com/.../index_FDS.html

The documentation about AM335x PWM in PSDK is below:

software-dl.ti.com/.../Foundational_Components_Kernel_Drivers.html

processors.wiki.ti.com/.../Processor_Linux_SDK_PWM

processors.wiki.ti.com/index.php/Sitara_Linux_LCDC_Porting_Guide

Regards,
Pavel

0 davidino brunelli over 6 years ago in reply to Pavel Botev

Prodigy 190 points

Hello Pavel,

thank you for you answer. So, if I understood correctly, it's not feasible with arago libraries, to start PWM e after a certain number of pulses, interrupt the PWM.

My last question is: Do you think that it's feasible to do this task using PRU microcontrollers?

Thank you.

Davidino

0 Nick Saulnier over 6 years ago in reply to davidino brunelli

TI__Guru** 102730 points

Hello Davidino,

You are correct, the PWM driver does not include a way to only output a certain number of pulses.

It is possible to use the PRU to control a PWM output. Take a look at my post here as a reference. (note: the PRU_ADC_onChip example is actually broken in SDK 5.1, please use the git repo tagged at PRU Software Support Package v5.4 or later, or SDK 5.2 or later).

Other resources:

This post discusses using eQEP on BeagleBones to control motors.

You have multiple options for timing in the PRU, like counting 5 ns clock cycles or using the IEP timer. In the software support package, see examples/am335x/PRU_IEP for a reference. Note that the resource_table does interrupt mapping, and the PRU code is in PRU_IEP.c.

Here and here are other potentially useful PRU/PWM posts.

Regards,

Nick

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Linux/PROCESSOR-SDK-AM335X: Library for am335x peripherals