Differential steering with a PCA8685 PWM Board *and* an L298N Motor Driver

Add this class to the file located at donkeycar/donkeycar/parts/actuator.py:

class Diff_PCA9685:
    '''
    Motor controlled with an L298N hbridge from the GPIO pins of a PC9685
    '''
    def __init__(self, channel_forward, channel_backward, channel_speed,
                 address=0x40, freq=60, busnum=None, init_delay=0.1):
        self.channel_forward = channel_forward
        self.channel_backward = channel_backward
        self.channel_speed = channel_speed

        self.default_freq = 60
        self.pwm_scale = freq / self.default_freq

        import Adafruit_PCA9685
        # Initialise the PCA9685 using the default address (0x40).
        if busnum is not None:
            from Adafruit_GPIO import I2C
            #replace the get_bus function with our own
            def get_bus():
                return busnum
            I2C.get_default_bus = get_bus
        self.pwm = Adafruit_PCA9685.PCA9685(address=address)
        self.pwm.set_pwm_freq(freq)
        time.sleep(init_delay) # "Tamiya TBLE-02" makes a little leap otherwise

    def run(self, speed):
        '''
        Update the speed of the motor where 1 is full forward and
        -1 is full backwards.
        '''
        if speed > 1 or speed < -1:
            raise ValueError( "Speed must be between 1(forward) and -1(reverse)")

        self.speed = speed
        self.throttle = int(dk.utils.map_range(abs(speed), 0, 1, 0, 4095))

        if self.speed > 0:
            self.pwm.set_pwm(self.channel_speed, 0, self.throttle)
            self.pwm.set_pwm(self.channel_forward, 0, 4095)
            self.pwm.set_pwm(self.channel_backward, 0, 0)
        elif self.speed < 0:
            self.pwm.set_pwm(self.channel_speed, 0, self.throttle)
            self.pwm.set_pwm(self.channel_forward, 0, 0)
            self.pwm.set_pwm(self.channel_backward, 0, 4095)
        else:
            self.pwm.set_pwm(self.channel_speed, 0, 0)
            self.pwm.set_pwm(self.channel_forward, 0, 0)
            self.pwm.set_pwm(self.channel_backward, 0, 0)

Add this option to the DRIVE_TRAIN_TYPE configurations in the file manage.py located at your Donkeycar instance directory:

elif cfg.DRIVE_TRAIN_TYPE == "PWM_TWO_WHEEL":
    from donkeycar.parts.actuator import TwoWheelSteeringThrottle, Diff_PCA9685

    left_motor = Diff_PCA9685(cfg.LEFT_FWD_CHANNEL, cfg.LEFT_BWD_CHANNEL, cfg.LEFT_SPD_CHANNEL)
    right_motor = Diff_PCA9685(cfg.RIGHT_FWD_CHANNEL, cfg.RIGHT_BWD_CHANNEL, cfg.RIGHT_SPD_CHANNEL)
    two_wheel_control = TwoWheelSteeringThrottle()
    V.add(two_wheel_control, 
            inputs=['throttle', 'angle'],
            outputs=['left_motor_speed', 'right_motor_speed'])

    V.add(left_motor, inputs=['left_motor_speed'])
    V.add(right_motor, inputs=['right_motor_speed'])

Remember to change the configuration file myconfig.py to use the camera option "WEBCAM":

# #CAMERA
CAMERA_TYPE = "WEBCAM"

As well as the drive train option that we created:

DRIVE_TRAIN_TYPE = "PWM_TWO_WHEEL"

And the correct channel for each motor:

RIGHT_SPD_CHANNEL  = 8 
RIGHT_FWD_CHANNEL  = 9 
RIGHT_BWD_CHANNEL  = 10
LEFT_SPD_CHANNEL = 13
LEFT_FWD_CHANNEL = 11
LEFT_BWD_CHANNEL = 12