Getting Started

This guide walks you through setting up your Raspberry Pi to control RC servos with BB.Servo.Pigpio.

Hardware Requirements

• Raspberry Pi (any model with GPIO pins)
• RC servo (standard hobby servo with 3-wire connector)
• 5V power supply for the servo (Pi's 5V pin can work for small servos)
• Jumper wires

Wiring

RC servos have three wires:

Basic Wiring Diagram

Raspberry Pi              Servo
-----------              -----
GPIO 17  ──────────────► Signal (orange)
5V       ──────────────► Power (red)
GND      ──────────────► Ground (brown)

Warning: For multiple servos or high-torque servos, use an external 5V power supply instead of the Pi's 5V pin. Connect the ground of the external supply to the Pi's ground.

Software Setup

1. Install pigpio

The pigpio library provides precise PWM timing for servo control.

# On Raspberry Pi OS
sudo apt-get update
sudo apt-get install pigpio

# Start the daemon
sudo pigpiod

# Optional: enable pigpiod to start on boot
sudo systemctl enable pigpiod

Verify pigpiod is running:

pigs t  # Should return the current tick count

2. Add Dependencies

Add bb_servo_pigpio and pigpiox to your mix.exs:

def deps do
  [
    {:bb, "~> 0.2"},
    {:bb_servo_pigpio, "~> 0.1"},
    {:pigpiox, "~> 0.1"}
  ]
end

Then fetch dependencies:

mix deps.get

3. Configure Pigpiox (Optional)

By default, pigpiox connects to pigpiod on localhost. If running remotely:

# config/config.exs
config :pigpiox,
  host: "192.168.1.100"  # IP of your Raspberry Pi

Verify Your Setup

Create a simple test to verify everything works:

# In IEx on your Raspberry Pi
iex> Pigpiox.Socket.command(:set_servo_pulsewidth, 17, 1500)
{:ok, 0}

This should move the servo to its centre position. If you see {:ok, 0}, your setup is working correctly.

Troubleshooting

"No such file or directory" error

The pigpio daemon isn't running:

sudo pigpiod

"Permission denied" error

Your user needs access to pigpio:

sudo usermod -a -G gpio $USER
# Log out and back in

Servo doesn't move

1. Check wiring connections
2. Verify the GPIO pin number matches your wiring
3. Try a different GPIO pin
4. Check servo power supply

Servo jitters or moves erratically

1. Add a capacitor (100µF) across servo power lines
2. Use a separate power supply for the servo
3. Keep signal wires away from motor/power wires

Next Steps

Now that your hardware is set up, proceed to Basic Usage to learn how to integrate servos into your BB robot.