checksum.py

"""ZDT V1.0.5 手册附录定义的校验算法。"""

from ..config import ChecksumType, parse_checksum_type, validate_motor_id


# 表值逐项来自《ZDT_X42S第二代闭环步进电机用户手册 V1.0.5》第109-110页。
CRC8_TABLE = (
    0x00, 0x5E, 0xBC, 0xE2, 0x61, 0x3F, 0xDD, 0x83,
    0xC2, 0x9C, 0x7E, 0x20, 0xA3, 0xFD, 0x1F, 0x41,
    0x9D, 0xC3, 0x21, 0x7F, 0xFC, 0xA2, 0x40, 0x1E,
    0x5F, 0x01, 0xE3, 0xBD, 0x3E, 0x60, 0x82, 0xDC,
    0x23, 0x7D, 0x9F, 0xC1, 0x42, 0x1C, 0xFE, 0xA0,
    0xE1, 0xBF, 0x5D, 0x03, 0x80, 0xDE, 0x3C, 0x62,
    0xBE, 0xE0, 0x02, 0x5C, 0xDF, 0x81, 0x63, 0x3D,
    0x7C, 0x22, 0xC0, 0x9E, 0x1D, 0x43, 0xA1, 0xFF,
    0x46, 0x18, 0xFA, 0xA4, 0x27, 0x79, 0x9B, 0xC5,
    0x84, 0xDA, 0x38, 0x66, 0xE5, 0xBB, 0x59, 0x07,
    0xDB, 0x85, 0x67, 0x39, 0xBA, 0xE4, 0x06, 0x58,
    0x19, 0x47, 0xA5, 0xFB, 0x78, 0x26, 0xC4, 0x9A,
    0x65, 0x3B, 0xD9, 0x87, 0x04, 0x5A, 0xB8, 0xE6,
    0xA7, 0xF9, 0x1B, 0x45, 0xC6, 0x98, 0x7A, 0x24,
    0xF8, 0xA6, 0x44, 0x1A, 0x99, 0xC7, 0x25, 0x7B,
    0x3A, 0x64, 0x86, 0xD8, 0x5B, 0x05, 0xE7, 0xB9,
    0x8C, 0xD2, 0x30, 0x6E, 0xED, 0xB3, 0x51, 0x0F,
    0x4E, 0x10, 0xF2, 0xAC, 0x2F, 0x71, 0x93, 0xCD,
    0x11, 0x4F, 0xAD, 0xF3, 0x70, 0x2E, 0xCC, 0x92,
    0xD3, 0x8D, 0x6F, 0x31, 0xB2, 0xEC, 0x0E, 0x50,
    0xAF, 0xF1, 0x13, 0x4D, 0xCE, 0x90, 0x72, 0x2C,
    0x6D, 0x33, 0xD1, 0x8F, 0x0C, 0x52, 0xB0, 0xEE,
    0x32, 0x6C, 0x8E, 0xD0, 0x53, 0x0D, 0xEF, 0xB1,
    0xF0, 0xAE, 0x4C, 0x12, 0x91, 0xCF, 0x2D, 0x73,
    0xCA, 0x94, 0x76, 0x28, 0xAB, 0xF5, 0x17, 0x49,
    0x08, 0x56, 0xB4, 0xEA, 0x69, 0x37, 0xD5, 0x8B,
    0x57, 0x09, 0xEB, 0xB5, 0x36, 0x68, 0x8A, 0xD4,
    0x95, 0xCB, 0x29, 0x77, 0xF4, 0xAA, 0x48, 0x16,
    0xE9, 0xB7, 0x55, 0x0B, 0x88, 0xD6, 0x34, 0x6A,
    0x2B, 0x75, 0x97, 0xC9, 0x4A, 0x14, 0xF6, 0xA8,
    0x74, 0x2A, 0xC8, 0x96, 0x15, 0x4B, 0xA9, 0xF7,
    0xB6, 0xE8, 0x0A, 0x54, 0xD7, 0x89, 0x6B, 0x35,
)


def xor_checksum(data):
    """
    @description         : 计算手册定义的逐字节异或校验
    @param data          : 地址、功能码和命令数据
    @return              : 0至255的校验码
    """
    value = 0
    for byte in bytes(data):
        value ^= byte
    return value


def crc8_checksum(data):
    """
    @description         : 使用手册附录查表算法计算CRC8
    @param data          : 地址、功能码和命令数据
    @return              : 0至255的CRC8
    """
    payload = bytes(data)
    if not payload:
        raise ValueError("CRC8 input must not be empty")
    crc8 = payload[0]
    for byte in payload[1:]:
        crc8 = CRC8_TABLE[crc8 ^ byte]
    return crc8


def calculate_checksum(checksum_type, address, body):
    """
    @description         : 按配置计算包含电机地址的ZDT校验码
    @param checksum_type : fixed_6b、xor或crc8
    @param address       : ZDT电机地址
    @param body          : 功能码加命令或返回数据，不含校验码
    @return              : 0至255的校验码
    """
    normalized_type = parse_checksum_type(checksum_type)
    normalized_address = validate_motor_id(address, allow_broadcast=True)
    serial_bytes = bytes((normalized_address,)) + bytes(body)
    if normalized_type is ChecksumType.FIXED_6B:
        return 0x6B
    if normalized_type is ChecksumType.XOR:
        return xor_checksum(serial_bytes)
    return crc8_checksum(serial_bytes)