BB Example: WidowX 200

Example Phoenix application demonstrating the Beam Bots robotics framework with a WidowX 200 robot arm.

Features

• Complete robot definition - 6-DOF arm with gripper using the BB DSL
• Web dashboard - Real-time control and 3D visualisation via bb_liveview
• Dynamixel integration - Hardware control via bb_servo_robotis
• Custom commands - Home position, demo circle, and torque control

Requirements

• Elixir ~> 1.15
• WidowX 200 robot arm (or run without hardware for simulation)
• U2D2 USB adapter at /dev/ttyUSB0 (configurable in robot definition)

Quick Start

# Install dependencies and build assets
mix setup

# Start the Phoenix server
mix phx.server

Visit localhost:4000 to access the robot dashboard.

Robot Definition

The robot is defined in lib/bb/example/wx200/robot.ex using the BB DSL:

defmodule BB.Example.WX200.Robot do
  use BB

  parameters do
    bridge(:robotis, {BB.Servo.Robotis.Bridge, controller: :dynamixel})
  end

  commands do
    command :home do
      handler(BB.Example.WX200.Command.Home)
      allowed_states([:idle])
    end
    # ... additional commands
  end

  controllers do
    controller(:dynamixel, {BB.Servo.Robotis.Controller,
      port: "/dev/ttyUSB0",
      baud_rate: 1_000_000,
      control_table: :xm430
    })
  end

  topology do
    link :base_link do
      joint :waist do
        # ... joint definition with actuator
        link :shoulder_link do
          # ... nested kinematic chain
        end
      end
    end
  end
end

Commands

Command	Description	Allowed States
arm	Enable torque and prepare for motion	[:disarmed]
disarm	Disable torque safely	[:idle]
home	Move all joints to zero position	[:idle]
demo_circle	Execute circular motion demo	[:idle]
disable_torque	Disable servo torque without state change	[:idle, :disarmed]

Execute commands via the web dashboard or programmatically:

{:ok, task} = BB.Example.WX200.Robot.home()
{:ok, :homed} = Task.await(task)

Project Structure

lib/
├── bb/example/wx200/
│   ├── robot.ex              # Robot DSL definition
│   └── command/              # Custom command handlers
│       ├── home.ex
│       ├── demo_circle.ex
│       └── disable_torque.ex
├── bb_example_wx200.ex       # Application context
├── bb_example_wx200/
│   └── application.ex        # Supervision tree
└── bb_example_wx200_web/     # Phoenix web layer
    ├── router.ex             # Mounts bb_dashboard
    └── ...

Development

mix test                      # Run tests
mix test path/to/test.exs:42  # Run single test at line
mix precommit                 # Pre-commit checks (compile, format, test)

Related Packages

• bb - Core framework
• bb_liveview - Phoenix LiveView dashboard
• bb_servo_robotis - Dynamixel servo driver
• bb_ik_fabrik - FABRIK inverse kinematics