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basic_bot.services.servo_control

Provides a service to control the servo motors using the PCA9685 PWM driver.

On startup, this service will look for a file named servo_config.yml in the directory where the service was started which should always be the root project dir of your basic_bot project. This file should contain a list of servos with the following format:

servos:
  - name: servo_name
    channel: 0
    motor_range: 180
    min_angle: 0
    max_angle: 180
    min_pulse: 500
    max_pulse: 2500

If you update the servo_config.yml file, you will need to restart the service.

The 'name' and 'channel' are required for each servo. The example above shows the default values for the other parameters.

  • name (required) is the unique name of the servo.
  • channel (required) is the channel on the PCA9685 board that the servo is connected to.
  • motor_range is the total manufacturer's range of the servo in degrees.
  • min_angle and max_angle are the minimum and maximum angles that the servo should be constrained.
  • min_pulse and max_pulse are the minimum and maximum pulse widths in microseconds that the servo will accept as specified by the manufacturer.

The service listens for messages on the central_hub key: "servo_angles". The message data should be a dictionary with keys that are the servo names from servo_config.yml and values that are the desired angle in degrees.

{
    "servo_angles": {
        "servo_name": 90
    }
}

The service will send a state update back to the central_hub with the current state of the servos using the key "servo_current_angles", for example: 

{
    "servo_actual_angles": {
        "servo_name": 90
    }
}

The service will also provide the current servo config as read from servo_config.yml at service startup using the key "servo_config", for example: 

{
    "servo_config": {
        "servos": [
            {
                "name": "servo_name",
                "channel": 0,
                "motor_range": 180,
                "min_angle": 0,
                "max_angle": 180,
                "min_pulse": 500,
                "max_pulse": 2500
            }
        ]
    }
}

ANGLE_UPDATE_FREQUENCY

seconds = 10Hz