KarmaBody

About

A Web app to access the effectors and sensors of a robot's body, real or simulated.

KarmaBody is responsible...

• For detecting the connected sensors and motors
• For providing, via HTTP, the list of sensors or motors, together with what they are* capable of and how to reach them
• For answering HTTP requests to sense and to act

Multiple platforms can be supported.

At the moment, only the EV3Dev-BrickPi3 platform is implemented (Lego EV3 devices connected to a BrickPi3 board on a Raspberry Pi3).

Getting started with the EV3Dev-BrickPi3 platform

Get yourself a Raspberry Pi3 and a BrickPi3

You'll also need a LEGO Mindstorms EV3 kit. It is, sadly, a retired product, but you'll easily find a second-hand kit for sale in the usual places.

Install Linux on the Raspberry Pi3 (RPI3)

The first step is to burn the EV3Dev ditribution of Linux on a micro SD Card.

• Follow isntructions in ev3dev.org to download zipped EV3Dev on RPI image
• Unzip the zipped image
  • Use WindowInstaller (open app on image)
• Follow the BrickPi3 instructions and in the config.txt file itself, and edit config.txt on the SD Card
• Plug SD Card in the RPI3, connect to ethernet both a PC and the RPI3
• Power up the RPI3
• On the PC, open an SSH session on the RPI3 by doing ssh [email protected]
  • The password is maker
• In the SSH session, do
  • sudo apt edit-sources, and add these to the apt sources

deb http://archive.debian.org/debian stretch main contrib non-free
#deb-src http://archive.debian.org/debian stretch main contrib non-free

#deb-src http://archive.ev3dev.org/debian stretch main

• Then do
  • sudo apt update
  • sudo apt-get install git curl build-essential autoconf

Enable WiFi on the RPI3

You'll want the RPI3 to network via WiFi.

• Enable and setup WiFi as instructed here

connmanctl
connmanctl> enable wifi
connmanctl> scan wifi
connmanctl> services
connmanctl> agent on 
connmanctl> connect wifi_...
connmanctl> quit

• Get the RPI3's ip address on wlan0 by doing ifconfig
• On the PC, edit /etc/hosts to add a brickpi3 alias for the ip address.

Create a user dev on the RPI3 and login as dev

The EV3Dev distribution comes with a pre-defined user named robot. Though it is not required, create a new user named dev and assign a password.

• In the RPI3 SSH session, do

  • sudo adduser dev
  • sudo usermod -aG sudo dev

• Close the SSH session

• Unplug the Ethernet cable from the RPI3

• Put the PC on the same wifi network enabled on the RPI3

• Start a new SSH session on the RPI3 with ssh dev@brickpi3

Reset the timezone

sudo dpkg-reconfigure tzdata

Install Erlang and Elixir using asdf

KarmaBody is an Elixir web app. It requires Erlang (the runtime platform) and Elixir (the programming language) to be installed.

The ASDF utility is used to do the installation.

• First, install ASDF

sudo apt install curl git
git clone https://github.com/asdf-vm/asdf.git ~/.asdf --branch v0.14.0

• Add to ~/.bashrc

. "$HOME/.asdf/asdf.sh"
. "$HOME/.asdf/completions/asdf.bash"
export KERL_CONFIGURE_OPTIONS="--disable-debug --without-javac"

• Install erlang with ASDF

source .bashrc
asdf plugin add erlang https://github.com/asdf-vm/asdf-erlang.git
sudo apt-get -y install libncurses5-dev
sudo apt-get -y install libssh-dev
asdf install erlang latest
asdf global erlang latest

• Install Elixir via asdf

asdf plugin-add elixir https://github.com/asdf-vm/asdf-elixir.git
asdf install elixir latest

• if asdf fails to install Elixir, do

cd ~
mkdir elixir
cd elixir
wget https://github.com/elixir-lang/elixir/releases/download/v1.16.1/elixir-otp-26.zip
unzip elixir-otp-26.zip

• Then, if not installing Elixir via asdf, add to .bashrc

export PATH=$PATH:$HOME/elixir/bin
source ~/.bashrc

Clone the Github repo

In an SSH session (ssh dev@brickpi3), clone the karma_body code repository on the RPI3.

cd ~
git clone https://github.com/jfcloutier/karma_body.git

To update to the latest,

• Open an SSH session on dev@brickpi3 and do

cd ~/karma_body
git pull

Connecting the BrickPi3 board

The BrickPi3 piggy-backs on the RPI3.

• Power off the RPI3
• Connect the BrickPi3 board to the RPI3
• Power on the RPI3 and open an SSH session to it via ssh dev@brickpi3
• Update its firmware if not running the latest by doing sudo update-brickpi3-fw
• Verify all is well with ev3dev-sysinfo

Configuration

The BrickPi3 board needs to be told what kinds of devices are connected to its ports.

The information is provided in ~/karma_body/config.exs. Edit the brickpi3 section to reflect the actual configuration of sensors and motors.

For example:

config :karma_body, :brickpi3,
  devices: [
    [port: :in1, sensor: :touch, position: :front, orientation: :forward],
    # [port: :in1, sensor: :gyro],
    [port: :in2, sensor: :light, position: :front, orientation: :downward],
    # The infrared sensor senses channels 1 and 2 of the IR beacon
    [port: :in3, sensor: :infrared, channels: [1, 2], position: :front, orientation: :forward],
    [port: :in4, sensor: :ultrasonic, position: :front, orientation: :forward],
    [
      port: :outA,
      motor: :tacho_motor,
      polarity: "normal",
      rpm: 60,
      burst_secs: 1,
      position: :left,
      orientation: :forward
    ],
    [
      port: :outB,
      motor: :tacho_motor,
      polarity: "normal",
      rpm: 60,
      burst_secs: 1,
      position: :right,
      orientation: :forward
    ]
    # [port: :outC, motor: :tacho_motor, polarity: "normal", rpm: 120, burst_secs: 5,position: :front, orientation: :downward]
  ],
  # If the brickpi3 is simulated, where to forward
  simulation: [host: "http://localhost:4001"]

The position and orientation properties are meaningful only when running in siumlation mode.

See ~/karma_body/lib/karma_body.ex for the names of all supported devices, and ~/karma_body/lib/karma_body/platform/brickpi3.ex for the list of all ports.

Run KarmaBody

To run karma_body,

• Open an SSH session on dev@brickpi3 and do

cd ~/karma_body
iex -S mix phx.server

REST API

Assuming the body is hosted at http://192.168.50.242:4000:

 $ wget -q -O - http://192.168.50.242:4000/api/sensors

{"sensors":[{"id":"touch_in1","type":"touch","url":"http://192.168.50.242:4000/api/sense/touch_in1/contact","capabilities":{"domain":["pressed","released"],"sense":"contact"}}]}

$ wget -q -O - http://192.168.50.242:4000/api/sense/touch_in1/contact

{"sensor":"touch_in1","sense":"contact","value":"released"}

Simulation mode

If the body is not running on an ev3dev system (with a BrickPi3 board), then the Brickpi3 platform is simulated.

When running in simulation mode, registering devices, sensing and actuating are dispatched to a simulation web app instead of accessing the file system where ev3dev drivers would otherwise expose sensor and motor devices.

The host of the simulation web app for the implemented platform, here :brickpi3, is identified in config/config.exs:

config :karma_body, :brickpi3,
  devices: [
   # ...
  ],
  # If the birckpi3 platform is simulated, where to forward device registration, sensing and actuating
  simulation: [host: "http://localhost:4001"]

The REST API of the simulation web app must conform to KarmaBody.Simulation.

Implementing other platforms

Alternate platforms can be added to the Body by implementing the KarmaBody.Platform behavior and by registering it in config/config.exs.

See KarmaBody.Platform.Brickpi3 as an example.