dxl_connection.py

import serial
import time

def lsb(value):
    return value & 0xff

def msb(value):
    return value >> 8


class SerialConnection:
    def __init__(self, port, baudrate):
        self._connection = serial.Serial()
        self._connection.port = port
        self._connection.baudrate = baudrate
        self._is_open = False

    def open(self):
        self._connection.open()
        self._is_open = True

    def close(self):
        self._connection.close()
        self._is_open = False

    def _write(self, values):
        for b in values:
            self._connection.write(chr(b))

    def send(self, id, reg, val):
        packets = [0xFF, 0xFF, id, 0x03 + len(val), 0x03, reg] + val
        checksum = 0
        for i in range(2, len(packets)):
            packet = packets[i]
            checksum = checksum + packet
        checksum = (~checksum) & 0xFF
        packets.append(checksum)
        self._write(packets)
        time.sleep(0.00002)

    def moving_speed(self, id, speed):
        self.send(id, 0x20, [lsb(speed), msb(speed)])

    def goal_position(self, id, position):
        self.send(id, 0x1E, [lsb(position), msb(position)])