3.6.2.8. Getting Started with PRU Software Support Package

Overview

Note

This section covers the software aspects of getting started with a PRU Subsystem (PRU-ICSS, PRU_ICSSG, PRU-SS). Hardware information, training material, software development resources, and more are in the Overview of PRU Subsystem

The PRU Software Support Package (PSSP) provides support for the PRU Subsystem in AM335x, AM437x, AM57xx, AM62x, AM64x, and AM65x devices. This package contains:

  • Support for ARM loading and initializing PRU via Remoteproc Linux driver

    • Remoteproc supports basic control functions such as firmware load, start/halt, simple debug, and interrupt managing

  • Support for communication between ARM and PRU via RPMsg Linux driver - RPMsg supports message passing

  • Basic firmware examples showing simple functionality

  • Register header files for easy register programming

  • Library/API for controlling vrings (used for RPMsg)

Things to Obtain

  • Code Composer Studio

  • PRU Code Generation Tools (you can also get these tools through the CCS App Center)

  • For an ARM running Linux:

    • Install the Linux Processor SDK for the device.

    • The PSSP is built into the Linux Processor SDK in the ‘<%SDK_INSTALL_DIR%>/example-applications/pru-icss-x.y.z’ folder

  • For an ARM running RTOS:


Installation of Tools

Tools installation paths are generally fairly arbitrary, but we do have a few requirements once you have installed to your preferred directory.

Linux

  1. Install Processor SDK to the directory of your choosing. Follow the installation instructions found at Getting Started Guide.

  2. If your Processor SDK Linux has a top-level example-applications folder, the PRU Software Support Package is built into the SDK at ‘example-applications/pru-icss-x.y.z/’. Otherwise you can download the files from the public Git repository here.

  3. (Optional) Install CCS to the directory of your choosing CCS installation instruction for Linux can be found here. Makefiles are provided in order to build all examples in the PRU Software Support Package. The ability to build the PRU projects using the Makefiles makes CCS optional in a Linux environment.


Windows

  1. Download the PRU files from the public Git repository here.

  2. Install CCS to the directory of your choosing Installers can be found here.


How to Enable PRU Support in Kernel

This step is used to enable the remoteproc driver in the Linux kernel. Windows users that are loading the PRU through CCS can safely skip this step during the development phase.

Beginning with Linux Processor SDK v2.0.2.11 the remoteproc and rpmsg modules are enabled by default and included out of the box in the Linux Processor SDK. Therefore, you do not need to make any menuconfig changes in order to load firmwares in the PRU cores.

How to Begin Programming

Programming the PRU core is not terribly different from programming any other core. Because we now have a C compiler we are able to write regular C code and have it perform tasks on the PRU cores. A great place to start development is to take a look at the PRU Getting Started Labs and PRU Hands-on Labs that are provided in the PSSP.

Register Header Files

Several register header files were created to help facilitate quick and easy configuration. In Linux, these are located in the <SDK_install_dir>/example-applications/pru-icss-x.y.z/include directory by default. In the Git repository these are located in the include folder. See the Header Files page for more information.


Special Considerations

There are a couple of special CPU registers available with different functionality.

  • Writes to R30 control the General Purpose Output pins, and reads allow the user to determine the current state of those pins

  • R31 is used to read General Purpose Input pins as well as the status of the two PRU host interrupts (bits 30 and 31)

    • Writes to R31 are used to generate interrupts - see the device-specific TRM for more information on how these work.

What Next?

For support please post questions on E2E Processor Support.