def crc8sae_j1850_bit(data):
"""
crc8sae_j1850_bit calculates the crc on an input byte array using the
method defined in the crc8sae_j1850 standard.
Arguments:
data - array of bytes in the format: ['\x00', '\x01', ...]
Returns:
crc - a single byte containing the crc of the input data bytes
Raises:
- Exception if any element of the input array is longer than 1 byte
- Exception if the length of the input array is greater than 7 bytes
"""
if len(data) > 7 or len(data) == 0:
raise Exception(
'Error: data length cannot excede 7 bytes')
crc = ord('\xff')
for byte in data:
if len(byte) > 1:
raise Exception(
'Error: data must be an array of strings of length 1')
else:
crc ^= ord(byte)
for k in range(0, 8):
if crc & ord('\x80'):
crc = (crc << 1) ^ ord('\x1d')
else:
crc = crc << 1
crc &= ord('\xff')
crc ^= ord('\xff')
return hex(crc)
if __name__ == "__main__":
msg_data = "21 01 51 50 00 00 00 00"
crc_num = 0
msg_data_list = msg_data.split(" ")
msg_list = [chr(int(b, 16)) for b in msg_data_list]
print("msg list is {}".format(msg_list))
msg_list.remove(msg_list[crc_num])
msg_data_list[crc_num] = crc8sae_j1850_bit(msg_list).replace("0x", "")
print("msg data list is {}".format(msg_data_list))
msg_data = " ".join(msg_data_list)
print("msg data is {}".format(msg_data))
