Example: Control Motors

This example demonstrates the various functionalities for motor control with the MotorGo Python API. The script sets up the MotorGo Plink board, configures the motor channels, and controls the motors in power and velocity modes. The script also reads the position and velocity of the motors from the encoders.

# spin_motors.py
# Before running this script, ensure that the MotorGo Plink is
# connected to the Raspberry Pi and that it has been flashed with the
# MotorGo firmware.
 
import time
 
from motorgo import BrakeMode, ControlMode, Plink
 
 
def main():
    # Create a Plink object, the main interface to the MotorGo board
    plink = Plink()
 
    # The first thing to set up for a Plink is the power supply voltage.
    # This is the voltage you are providing to the Plink on the barrel jack.
    # If this is the battery, make sure this is the charged voltage.
    plink.power_supply_voltage = 9.0
 
    # The Plink object has 4 MotorChannel objects, corresponding to the 4 motor channels
    # on the board
    # You can access them directly: plink.channel1
    # Or you can save references as local variables for convenience:
    left_motor = plink.channel1
    right_motor = plink.channel2
 
    # Next, you need to set the motor voltage limit.
    # This is the maximum voltage your motor channels will output to protect the motors.
    # The voltage limit is 0 by default, which means the motors will not move if this is not set.
    left_motor.motor_voltage_limit = 6.0
    right_motor.motor_voltage_limit = 6.0
    plink.channel3.motor_voltage_limit = 6.0
    plink.channel4.motor_voltage_limit = 6.0
 
    # Finally, connect to the MotorGo board and psuh the configuration
    plink.connect()
 
    # You can configure how you want to control the motor channels.
    # Power mode: Set the power of the motor in the range [-1, 1]
    #            This directly corresponds to setting a voltage to the motor
    #
    # Velocity mode: Set the velocity of the motor in rad/s
    #              This mode requires setting the velocity PID gains
    #              It also requires an encoder to be connected to the motor
    left_motor.control_mode = ControlMode.POWER
    right_motor.control_mode = ControlMode.VELOCITY
    plink.channel3.control_mode = ControlMode.POWER
    plink.channel4.control_mode = ControlMode.POWER
 
    # If you are using ControlMode.VELOCITY, you must set the velocity PID gains
    right_motor.set_velocity_pid_gains(4.5, 0.1, 0.0)
 
    while True:
 
        # Set motor powers
        # Set the power command in the range [-1, 1]
        left_motor.power_command = 0.5
 
        # Set the velocity command in rad/s
        right_motor.velocity_command = 1.2
 
        # Set the power command in the range [-1, 1]
        plink.channel3.power_command = 0.25
        plink.channel4.power_command = -0.25
 
        # You can read the position and velocity of the motor channels from the encoders
        print("----")
        print(
            f"Channel 1 position: {plink.channel1.position}, velocity: {plink.channel1.velocity}"
        )
        print(
            f"Channel 2 position: {plink.channel2.position}, velocity: {plink.channel2.velocity}"
        )
        print(
            f"Channel 3 position: {plink.channel3.position}, velocity: {plink.channel3.velocity}"
        )
        print(
            f"Channel 4 position: {plink.channel4.position}, velocity: {plink.channel4.velocity}"
        )
        print("----")
 
        time.sleep(0.01)
 
 
if __name__ == "__main__":
    main()

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