A controller that manages a PCA9685 PWM device.

This controller wraps a PCA9685.Device process and provides an interface for actuators to set servo pulse widths. Multiple actuators can share a single controller, with each actuator controlling a different channel (0-15).

Configuration

The controller is typically defined in the robot DSL:

controller :pca9685, {BB.Servo.PCA9685.Controller,
  bus: "i2c-1",
  address: 0x40,
  pwm_freq: 50
}

Options

• :bus - (required) The I2C bus name, e.g., "i2c-1"
• :address - (required) The I2C address of the PCA9685, e.g., 0x40
• :pwm_freq - PWM frequency in Hz (default: 50, suitable for servos)
• :oe_pin - Optional GPIO pin for output enable control

Safety

This controller implements the BB.Controller behaviour. When the robot is disarmed or crashes, the OE pin is pulled high to disable all servo outputs. If no OE pin is configured, the disarm callback returns :ok (individual actuators handle their own channel disarm).

Both the I2C bus handle and the OE GPIO live inside the wrapped device process, so disarm/1 can only reach the hardware while the controller process is alive. If the controller has crashed or is wedged, the disarm call fails and returns {:error, reason}, driving the robot into the :error state rather than falsely reporting success. For a hardware-independent kill that survives a dead controller, wire an :oe_pin: a clean controller shutdown pulls it high via the device's terminate/2.