PRU Information

Steps to get up and running

• Start with RCN latest flasher image (www.rcn-ee.net)
• PRU Package that needs to be installed: https://github.com/beagleboard/am335x_pru_package
• Install device Tree compiler (DTC) from
  • patch for DTC compiler "for -@ symbol"

$ git clone git://www.jdl.com/software/dtc.git
$ cd dtc
$ git checkout 27cdc1b16f86f970c3c049795d4e71ad531cca3d
$ wget https://github.com/beagleboard/meta-beagleboard/raw/master/common-bsp/recipes-kernel/dtc/dtc/0001-dtc-Dynamic-symbols-fixup-support.patch
$ patch -p1 < 0001-dtc-Dynamic-symbols-fixup-support.patch
$ make

• DTC used to
  • modify device tree overlay
  • Fragment for one ultrasonic : https://github.com/Teknoman117/beaglebot/blob/master/hcsr04-demo/hcsr04_demo.dts
  • Need to modify for 4 sensors and specific pins
    • the pins selected are the guaranteed realtime access pins
  • device tree overlay must be referenced by main device tree file (dts -> dtb)
    • /boot/uboot/dtbs/am335x-boneblack.dts
    • decompile am335x-boneblack.dtb to produce editable dts
    • reference that added take from element14 example
  • compiled fragment ends /lib/firmware
  • fragment gets loaded by "echo (fragment_name) > $SLOTS"

/*
* pru dts file BB-BONE-PRU-00A0.dts
*/
/dts-v1/;
/plugin/;

/ {
  compatible = "ti,beaglebone", "ti,beaglebone-black";

  /* identification */
  part-number = "PRU_US";
  version = "00A0";

  fragment@0 {
    target = <&am33xx_pinmux>;
    __overlay__ {
      mygpio: pinmux_mygpio{
        pinctrl-single,pins = <
            0x834 0x06  /* P8_11 out, MODE6 trigger */
                        /* 0x830 0x06   P8_12 out, MODE6 trigger */
            0x83C 0x36  /* P8_15 in,  MODE6, pullup echo */
                        /* 0x838 0x36   P8_16 in,  MODE6, pullup echo */
                        /* 0x99C 0x05   P9_28 out, MODE5 trigger */
                        /* 0x994 0x05  P9_29 out, MODE5 trigger */
                        /* 0x998 0x36  P9_30 in, MODE6, pullup echo */
                        /* 0x990 0x36  P9_31 in, MODE6,pullup echo */
          >;
      };
    };
  };

  fragment@1 {
    target = <&ocp>;
    __overlay__ {
        test_helper: helper {
        compatible = "bone-pinmux-helper";
        pinctrl-names = "default";
        pinctrl-0 = <&mygpio>;
        status = "okay";
      };
    };
  };

 fragment@2{
  target = <&pruss>;
    __overlay__ {
      status = "okay";
    };
  };
};

Code for PRUs

• PRU code (one sensor): https://github.com/Teknoman117/beaglebot/blob/master/hcsr04-demo/hcsr04_demo.p

  • Needs to be assembled into a *.bin file using "pasm" program (look in makefile)
  • see AM335x PRU reference guide starting at page 36

• *.c file

  • uses prussdrv libraries
  • initializes PRU, prepares to receive a program
  • loads bin file using prussdrv_exec_program
  • docs for PRU functions in ???
  • python wrapper may exist

• Consult BeagleBone Black Pin Assignments in drive, Sheet 5 for pinmux

• sub-centimeter should be possible

Best starting point for PRU examples: http://www.element14.com/community/community/knode/single-board_computers/next-gen_beaglebone/blog/2013/05/22/bbb--working-with-the-pru-icssprussv2

Ultrasonic Demo https://github.com/PaladinEng/beaglebot/tree/master/hcsr04-demo

Setting up PRU on BBB

• BeagleBone Black: Introduction to PRU-ICSS

* [Working with the PRU-ICSS/PRUSSv2](http://www.element14.com/community/community/knode/single-board_computers/next-gen_beaglebone/blog/2013/05/22/bbb--working-with-the-pru-icssprussv2)

PRU Instruction set Wiki

• PRU Software Development

AM335x PRU-ICSS Reference Guide Download

• GitHub Download

Some Examples of Others Using PRUs

• Representation of a sinusoidal wave using pulse width modulation

* [Imaging with a PRU connected Camera](http://www.element14.com/community/community/knode/single-board_computers/next-gen_beaglebone/blog/2013/08/18/bbb--imaging-with-a-pru-connected-camera)