AM335x PRU <-> Linux communication

Tim Hoeppner50

I'm looking for an example of communication between PRU and Linux. My specific application will be streaming very low bandwidth data between PRU -> Linux.

My setup consists of:
AM335x Linux SDK (ti-processor-sdk-linux-am335x-evm-01.00.00.00-Linux-x86), couldn’t use the latest one since the PRU support package only supports up to this version.
PRU Addon Package (pru-addon-v2.0-Linux-x86)
CCS (CCS6.1.0.00104_linux)

My tests are run on a BeagleBone Black with the latest stock debian image but with the kernel replaced with the one from TI (above).

There seems to be some community support for communication between the processors for older kernels but the support package from TI uses the 3.14 kernel with different drivers. I've successfully built and run lab examples in Linux using the remoteproc driver but I can't find any examples which show communication between the PRU and Linux. I found a set of slides which mention the rpmsg driver but I don't know how to use it.

The examples in SDK/example-applications/pru/examples/ fail to include any Linux userspace companion programs for any of the PRU <-> ARM examples.

Thanks for any help,
Tim

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

Hi Tim,

I will ask the PRU experts to help on this.

0 Jason Reeder over 8 years ago in reply to Biser Gatchev-XID

TI__Genius 10415 points

Tim,

RPMsg support on the PRU side is under development and will be released in the next version of the PRU Addon Package that will install on top of the 1.00.00.03 release of the Processor SDK.

There is a dev branch on our git repo found here (https://git.ti.com/pru-software-support-package/pru-software-support-package/trees/dev) where you can follow the development if you'd like.

There are 4 echo examples in the 'examples' folder that make use of the new PRU RPMsg library. The source code for the new library is found in the 'src/rpmsg_lib' folder. The library itself (rpmsg_lib.lib) is found in the 'lib' folder.

There are also 5 additional patches in the 'patches' folder (0014-0018) that will correct some small bugs as well as add a new Linux driver that will allow an RPMsg channel to show up as a character device under /dev/ in your Linux filesystem.

This is unreleased/development code so there won't be full collateral or support available until the next Addon Package is released. But, hopefully you can look through the code and have a leg up once the release hits.

Jason Reeder

0 Tim Hoeppner50 over 8 years ago in reply to Jason Reeder

Prodigy 185 points

Jason,

Thanks for the update, I'll be following along.

Do you have an estimate on when this might be completed?

Tim

0 Jason Reeder over 8 years ago in reply to Tim Hoeppner50

TI__Genius 10415 points

Tim,

I'm pushing to finalize the code within the next week and a half. There are some steps on our end between code finalization and the package showing up on ti.com but I'm hopeful for an August release time frame.

Jason Reeder

0 Tim Hoeppner50 over 8 years ago in reply to Jason Reeder

Prodigy 185 points

Jason, I've been following your work closely and just noticed you tagged the 3.0.0 release in git. This prompted me to check the download page which looks like it now includes the updated package. Thank you for your commitment in finishing this within your estimated time frame. I'll be testing this out as soon as possible.

0 Jason Reeder over 8 years ago in reply to Tim Hoeppner50

TI__Genius 10415 points

Tim,

This post was on my list of posts to notify of the new package. Glad you've found it already.

I've added labs 5 and 6 to the hands-on labs section of the PRU wiki that show how to use the RPMsg communication (processors.wiki.ti.com/.../PRU_Training:_Hands-on_Labs). Be sure you've completed at least lab 4 before starting 5 and 6.

Let me know if you run into any issues while going through the new labs and I'll update the wiki instructions.

Jason Reeder

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AM335x PRU <-> Linux communication