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Building a DeepRacer for Raspberry Pi 4

Features

Main features of the port:

  • Previously trained models will work
  • Uses Tensorflow Lite or OpenVINO for inference. Supports the Intel Neural Compute Stick 2 (NCS2/MYRIAD)
  • Can integrate with DREM
  • Single power source¹ - reduces weight and lowers center of gravity
  • Over-the-Air Software Updates

Parts

The following parts are needed:

  • WLToys A979 (or compatible) or original DeepRacer
  • 3D-print of the parts in /drawing.
  • Chassis holder TODO
  • Raspberry Pi 4, recommended 2GB or more of RAM
    • Stand-off set (2.5mm)
  • Waveshare Servo Driver Hat or compatible PCA9865 servo boards.
    • Stackable header 40pin (to get higher servo driver hat higher than the fan)
  • Raspberry Pi Camera 2
    • Longer cable (20-25cm)
    • Screws M2x15mm + nuts
  • Recommended cooling fan: GeeekPi Raspberry Pi 4 Armor Lite
  • RGB Led:
  • Servo extension cable (with red cable cut)
  • 3-pin female JST
  • 2.5mm plastic screws (preferrably of good quality) to mount back and front; or use M2 screws with nuts

¹ The Waveshare hat comes with a step-down converter from 7.4V to 5V, and will power the Pi via the GPIO header. Other similar cards will require separate power.

Software Install

Installation of software is reasonably straight forward, as pre-built packages are provided:

  • Flash an SD card with Ubuntu 22.04 Server for ARM64 using the Raspberry Pi Imager.
  • Boot the SD card, and let it upgrade (this takes some time...)
  • Run git clone https://github.com/aws-deepracer-community/deepracer-custom
  • Run sudo ./install_scripts/pi/install-prerequisites.sh
  • Reboot
  • Run sudo ./install_scripts/pi/install-deepracer.sh

Once installed you can start the stack with sudo /opt/aws/deepracer/start_ros.sh. To ensure a smooth start a camera needs to be plugged in. The launch log will now display in the console.

To automatically start at boot do sudo systemctl enable deepracer-core and to start the service in the background sudo systemctl start deepracer-core.

Changes

Some changes have been made to the code to enable access to GPIO as sysfs layout is different on the Raspberry Pi than on the custom Intel board.

Improvements

Details

PWM Outputs

Channel Purpose Notes
0 Speed controller Remove red cable for stock DeepRacer ESC
1 Steering servo
2 RGB LED Tail light - Red
3 RGB LED Tail light - Green
4 RGB LED Tail light - Blue
5
6
7 RGB LED
8 RGB LED
9 RGB LED
10 RGB LED
11 RGB LED
12 RGB LED
13 RGB LED
14 RGB LED
15 RGB LED

NOTE: Remove the red cable on the stock DeepRacer from the speed controller into PWM channel 0, otherwise you are putting 6V into the servo hat.

LiPo can power both the board and car, 3 pin (balance lead) gets wired to VIN (black and red cables only) to power the board and RPi. The 2 pin power cable goes to the car as normal.

GPIO layout:

  • gpio1 - enables PWM (does not do anything, PWM is always on for the Waveshare board)
  • gpio495-gpio504 - maps to PWM7 to PWM15 on the Hat, to control three RGB leds (those originally on the side of the board)

USB host mode: To connect the USB-C port on the Raspberry Pi 4 to a USB on your computer, then you need to perform two changes:

  • Add dtoverlay=dwc2,dr_mode=host to your /boot/firmware/config.txt
  • Add modules-load=dwc2,g_ether to your /boot/firmware/cmdline.txt

With this you will see a new network connect appear in Windows (and Mac?). The Raspberry Pi will have IP 10.0.0.1; you can connect to the console via https://deepracer.aws. This will require your computer to be disconnected from all other networks (given a DNS priority issue). SSH directly to the IP will work.

What does not (yet) work

  • Battery gauge is not connected - red warning message persists
  • Device Info Node is looking in non-existent places - no real impact