Python example of how to send and receive serial messages from a BaseCam gimbal with SimpleBGC 32-bit controller.

rotate_gimbal.py

from collections import namedtuple

import serial
import struct

# outgoing CMD_CONTROL - control gimbal movement
ControlData = namedtuple(
    'ControlData',
    'roll_mode pitch_mode yaw_mode roll_speed roll_angle pitch_speed pitch_angle yaw_speed yaw_angle')

Message = namedtuple(
    'Message',
    'start_character command_id payload_size header_checksum payload payload_checksum')


def pack_control_data(control_data: ControlData) -> bytes:
    return struct.pack('<BBBhhhhhh', *control_data)


def create_message(command_id: int, payload: bytes) -> Message:
    payload_size = len(payload)
    return Message(start_character=ord('>'),
                   command_id=command_id,
                   payload_size=payload_size,
                   header_checksum=(command_id + payload_size) % 256,
                   payload=payload,
                   payload_checksum=sum(payload) % 256)


def pack_message(message: Message) -> bytes:
    message_format = '<BBBB{}sB'.format(message.payload_size)
    return struct.pack(message_format, *message)


def unpack_message(data: bytes, payload_size: int) -> Message:
    message_format = '<BBBB{}sB'.format(payload_size)
    return Message._make(struct.unpack(message_format, data))


def read_message(connection: serial.Serial, payload_size: int) -> Message:
    # 5 is the length of the header + payload checksum byte
    # 1 is the payload size
    response_data = connection.read(5 + payload_size)
    print('received response', response_data)
    return unpack_message(response_data, payload_size)


def rotate_gimbal():
    CMD_CONTROL = 67
    control_data = ControlData(roll_mode=1, roll_speed=0, roll_angle=0,
                               pitch_mode=1, pitch_speed=0, pitch_angle=0,
                               yaw_mode=1, yaw_speed=100, yaw_angle=0)
    print('command to send:', control_data)
    packed_control_data = pack_control_data(control_data)
    print('packed command as payload:', packed_control_data)
    message = create_message(CMD_CONTROL, packed_control_data)
    print('created message:', message)
    packed_message = pack_message(message)
    print('packed message:', packed_message)

    connection = serial.Serial('/dev/ttyUSB0', baudrate=115200, timeout=10)
    print('send packed message:', packed_message)
    connection.write(packed_message)
    message = read_message(connection, 1)
    print('received confirmation:', message)
    print('confirmed command with ID:', ord(message.payload))


if __name__ == '__main__':
    rotate_gimbal()

Hi, i would like to use this script and edit it. may i check if this script needs any other libraries or dependencies installed? or i can simply run it once connected to the BGC board via usb.

You need to install pyserial. Connect the BGC board to your (Linux) computer. Turn/power on the board. It is expected to be mounted as /dev/ttyUSB0 (see line 61). Then you can just run the script and the gimbal should start rotating. You need to stop the rotation manually, i.e. using hardware buttons on the gimbal.

This script was a proof of concept. I wrote a library for SimpleBGC as part of an ongoing project. The library is not available on pypi yet. serial_example.py rotates the gimbal in one direction, rotates back after 3 seconds and stops after another 3 seconds.

Which gimbal are you using?

Hi, what are the different modes for roll_mode, pitch_mode, yaw_mode? thanks

@jpp-coremarine See CONTROL_MODE of CMD_CONTROL in serial API specification (page 49). The mentioned library has the values typed as an enum ControlMode.

@jpp-coremarine See CONTROL_MODE of CMD_CONTROL in serial API specification (page 49). The mentioned library has the values typed as an enum ControlMode.

Got it! Thanks a lot!

Hi @maiermic , can you share the hardware connection that is used for this code to run?

@Icebearbear You need a BaseCam gimbal with SimpleBGC 32-bit controller connected to a Linux computer via USB. The code assumes (see line 61) that it is mounted as /dev/ttyUSB0. Do you have troubles to connect? Which hardware are you using?