Trying to Make a 3 DoF Arm with Mini Maestro 18

Robotics and electronics discussion Software and microcontrollers
1 
def set_target_one(device, position, servo=1):
    """Sends the target position to a specific servo channel using a control transfer."""
    # bmRequestType = 0x40 (Vendor-defined request, host-to-device direction)
    bm_request_type = 0x40
    b_request = REQUEST_SET_TARGET

    # Value parameter requires position in quarter-microseconds (input * 4)
    w_value = int(position * 4)
    w_index = int(servo)

    try:
        # usb.core.Device.ctrl_transfer(bmRequestType, bRequest, wValue, wIndex, data_or_wLength, timeout)
        device.ctrl_transfer(
            bm_request_type, b_request, w_value, w_index, data_or_wLength=0, timeout=5000
        )
    except usb.core.USBError as e:
        print(f"USB Transfer failed: {e}", file=sys.stderr)

Currently, I can only move one servo at a time. This is a blocker for the arm I am producing.

And…

One of the servos controlled via the Maestro 18-Channel module seems to like to spin freely when given commands. It listens to 0 being a stop function but spins in only one direction freely at the same speed no matter if I choose 1 or 180 for its start to stop procedure.

See the below code for this effort:

def main():
    print("Searching for Pololu Maestro device...")
    device = find_maestro_device()

    if device is None:
        print("Error: Maestro device not found. Check physical connections or permissions.")
        sys.exit(1)

    print("Device found and initialized successfully.")
    servo_channel = '0'
    servo_channel = '1'
    servo_channel = '2'

    try:
        while True:
            user_input = input("Enter position (or 'q' to quit): ").strip()
            if user_input.lower() == "q":
                break

            try:
                position = int(user_input)
                set_target_zero(device, position, servo_channel)

                set_target_one(device, position, servo_channel)
                set_target_two(device, position, servo_channel)

            except ValueError:
                print("Invalid input. Please enter an integer number.")

    except KeyboardInterrupt:
        print("\nExiting program.")
    finally:
        # PyUSB handles closing the device and recycling handles implicitly on exit,
        # but clearing configurations ensures safe detachment.
        usb.util.dispose_resources(device)


if __name__ == "__main__":
    main()

Does anyone see what I may be doing versus what needs to be done so that I can control the Maestro 18-Channel servo module with more control?

Seth