reachymini_vn_example / dynamixel.py
Steve Nguyen
init
b52ebca
"""Dynamixel Protocol 2.0 implementation in Python."""
from typing import List, Tuple
def crc16_update(crc_accum: int, data: bytes) -> int:
"""Update CRC16 with new data."""
crc_table = [
0x0000, 0x8005, 0x800F, 0x000A, 0x801B, 0x001E, 0x0014, 0x8011,
0x8033, 0x0036, 0x003C, 0x8039, 0x0028, 0x802D, 0x8027, 0x0022,
0x8063, 0x0066, 0x006C, 0x8069, 0x0078, 0x807D, 0x8077, 0x0072,
0x0050, 0x8055, 0x805F, 0x005A, 0x804B, 0x004E, 0x0044, 0x8041,
0x80C3, 0x00C6, 0x00CC, 0x80C9, 0x00D8, 0x80DD, 0x80D7, 0x00D2,
0x00F0, 0x80F5, 0x80FF, 0x00FA, 0x80EB, 0x00EE, 0x00E4, 0x80E1,
0x00A0, 0x80A5, 0x80AF, 0x00AA, 0x80BB, 0x00BE, 0x00B4, 0x80B1,
0x8093, 0x0096, 0x009C, 0x8099, 0x0088, 0x808D, 0x8087, 0x0082,
0x8183, 0x0186, 0x018C, 0x8189, 0x0198, 0x819D, 0x8197, 0x0192,
0x01B0, 0x81B5, 0x81BF, 0x01BA, 0x81AB, 0x01AE, 0x01A4, 0x81A1,
0x01E0, 0x81E5, 0x81EF, 0x01EA, 0x81FB, 0x01FE, 0x01F4, 0x81F1,
0x81D3, 0x01D6, 0x01DC, 0x81D9, 0x01C8, 0x81CD, 0x81C7, 0x01C2,
0x0140, 0x8145, 0x814F, 0x014A, 0x815B, 0x015E, 0x0154, 0x8151,
0x8173, 0x0176, 0x017C, 0x8179, 0x0168, 0x816D, 0x8167, 0x0162,
0x8123, 0x0126, 0x012C, 0x8129, 0x0138, 0x813D, 0x8137, 0x0132,
0x0110, 0x8115, 0x811F, 0x011A, 0x810B, 0x010E, 0x0104, 0x8101,
0x8303, 0x0306, 0x030C, 0x8309, 0x0318, 0x831D, 0x8317, 0x0312,
0x0330, 0x8335, 0x833F, 0x033A, 0x832B, 0x032E, 0x0324, 0x8321,
0x0360, 0x8365, 0x836F, 0x036A, 0x837B, 0x037E, 0x0374, 0x8371,
0x8353, 0x0356, 0x035C, 0x8359, 0x0348, 0x834D, 0x8347, 0x0342,
0x03C0, 0x83C5, 0x83CF, 0x03CA, 0x83DB, 0x03DE, 0x03D4, 0x83D1,
0x83F3, 0x03F6, 0x03FC, 0x83F9, 0x03E8, 0x83ED, 0x83E7, 0x03E2,
0x83A3, 0x03A6, 0x03AC, 0x83A9, 0x03B8, 0x83BD, 0x83B7, 0x03B2,
0x0390, 0x8395, 0x839F, 0x039A, 0x838B, 0x038E, 0x0384, 0x8381,
0x0280, 0x8285, 0x828F, 0x028A, 0x829B, 0x029E, 0x0294, 0x8291,
0x82B3, 0x02B6, 0x02BC, 0x82B9, 0x02A8, 0x82AD, 0x82A7, 0x02A2,
0x82E3, 0x02E6, 0x02EC, 0x82E9, 0x02F8, 0x82FD, 0x82F7, 0x02F2,
0x02D0, 0x82D5, 0x82DF, 0x02DA, 0x82CB, 0x02CE, 0x02C4, 0x82C1,
0x8243, 0x0246, 0x024C, 0x8249, 0x0258, 0x825D, 0x8257, 0x0252,
0x0270, 0x8275, 0x827F, 0x027A, 0x826B, 0x026E, 0x0264, 0x8261,
0x0220, 0x8225, 0x822F, 0x022A, 0x823B, 0x023E, 0x0234, 0x8231,
0x8213, 0x0216, 0x021C, 0x8219, 0x0208, 0x820D, 0x8207, 0x0202
]
for byte in data:
i = ((crc_accum >> 8) ^ byte) & 0xFF
crc_accum = ((crc_accum << 8) ^ crc_table[i]) & 0xFFFF
return crc_accum
def build_packet(motor_id: int, instruction: int, params: List[int]) -> bytes:
"""Build a Dynamixel Protocol 2.0 packet."""
# Header
packet = bytearray([0xFF, 0xFF, 0xFD, 0x00])
# ID
packet.append(motor_id)
# Length (instruction + params + CRC)
length = len(params) + 3
packet.append(length & 0xFF)
packet.append((length >> 8) & 0xFF)
# Instruction
packet.append(instruction)
# Parameters
packet.extend(params)
# CRC
crc = crc16_update(0, bytes(packet))
packet.append(crc & 0xFF)
packet.append((crc >> 8) & 0xFF)
return bytes(packet)
def ping_packet(motor_id: int) -> bytes:
"""Create a ping packet."""
return build_packet(motor_id, 0x01, [])
def torque_enable_packet(motor_id: int, enable: bool) -> bytes:
"""Create a torque enable/disable packet."""
# Write instruction: Address (2 bytes) + Data
# Address 64 (Torque Enable), 1 byte data
return build_packet(motor_id, 0x03, [64, 0, 1 if enable else 0])
def goal_position_packet(motor_id: int, position: int) -> bytes:
"""Create a goal position packet."""
# Write instruction: Address (2 bytes) + Data (4 bytes)
# Address 116 (Goal Position)
return build_packet(motor_id, 0x03, [
116, 0, # Address (low byte, high byte)
position & 0xFF,
(position >> 8) & 0xFF,
(position >> 16) & 0xFF,
(position >> 24) & 0xFF
])
def parse_status_packet(data: bytes) -> Tuple[bool, str]:
"""Parse a status packet and return (success, message)."""
if len(data) < 11:
return False, f"Packet too short: {len(data)} bytes"
# Check header
if data[0] != 0xFF or data[1] != 0xFF or data[2] != 0xFD or data[3] != 0x00:
return False, "Invalid header"
motor_id = data[4]
length = data[5] | (data[6] << 8)
instruction = data[7]
error = data[8]
if error != 0:
return False, f"Motor error: {error:#04x}"
return True, f"OK (ID: {motor_id})"