Pololu A-Star 32U4 - Elixir Library

An Elixir library for controlling the Pololu A-Star 32U4 board when operating in RPi slave mode via I2C communication.

Features

• 🚦 LED Control - Control yellow, green, and red LEDs
• 🎮 Button Reading - Read states of buttons A, B, and C
• 🚗 Motor Control - Control left and right motors with speed values
• 🔋 Battery Monitoring - Read battery voltage in millivolts
• 📊 Analog Sensors - Read 6 analog input channels (0-1023)
• 🎵 Audio - Play melodies using note strings
• 📏 Encoders - Read motor encoder values

Installation

Add pololu_a_star_32u4 to your list of dependencies in mix.exs:

def deps do
  [
    {:pololu_a_star_32u4, "~> 0.1.0"}
  ]
end

Hardware Setup

1. A-Star 32U4 Board: Flash the RPi slave firmware to your A-Star 32U4

2. I2C Connection: Connect the board to your Raspberry Pi

3. I2C Enable: Ensure I2C is enabled on your Raspberry Pi device

Quick Start

# Control LEDs
PololuAStar32u4.set_leds(yellow: true, green: false, red: false)

# Read buttons
buttons = PololuAStar32u4.read_buttons()
# => %{a: false, b: true, c: false}

# Control motors (speed: -400 to 400)
PololuAStar32u4.set_motors(left: 200, right: 200)

# Read battery voltage
battery_mv = PololuAStar32u4.read_battery_mv()
# => 11700 (11.7V)

# Read analog sensors
analog = PololuAStar32u4.read_analog()
# => [512, 0, 1023, 256, 768, 100]

# Play a melody
PololuAStar32u4.play_song("c4e4g4c5")

# Read motor encoders
{left, right} = PololuAStar32u4.read_encoders()
# => {1250, -800}

Livebook Integration

For interactive development and testing, use the included Livebook:

1. Open livebook_test.livemd in Livebook
2. Run the cells to test different functions
3. Monitor your robot's sensors in real-time

API Reference

LED Control

PololuAStar32u4.set_leds(yellow: boolean, green: boolean, red: boolean)

Button Reading

PololuAStar32u4.read_buttons()
# Returns: %{a: boolean, b: boolean, c: boolean}

Motor Control

PololuAStar32u4.set_motors(left: integer, right: integer)
# Speed range: -400 to 400

Sensor Reading

# Battery voltage in millivolts
PololuAStar32u4.read_battery_mv()

# Analog sensors (6 channels, 0-1023)
PololuAStar32u4.read_analog()

# Motor encoders
PololuAStar32u4.read_encoders()

Audio

PololuAStar32u4.play_song("c4e4g4c5")

I2C Protocol Details

The library implements the A-Star 32U4 RPi slave protocol:

• Address: 0x14
• Bus: i2c-1 (default)
• Protocol: Write register offset, then read/write data
• Timing: 1ms delay between operations

Register Map

Error Handling

The library includes robust error handling:

• I2C connection failures are logged and reported
• Graceful degradation when hardware is unavailable
• Configurable auto-start for development environments

Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -am 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Pololu A-Star 32U4 Robot controller for the A-Star 32U4 board
• Circuits.I2C for I2C communication