CRC8 Maxim/Dallas for Python

crc8dallas.py

############################################
# This is for CRC-8 Maxim/Dallas Algorithm
# Improved with less variable and functions
# Supports both Python3.x and Python2.x
# Has append and check functions
# When standalone, can read from either arguments or stdin
# Writes to stdout cleaner
# http://gist.github.com/eaydin
############################################

import binascii
import sys
if sys.version_info[0] == 3:
    import codecs

def calc(incoming):
    # convert to bytearray
    if sys.version_info[0] == 3:
        hex_data = codecs.decode(incoming, "hex_codec")
    else:
        hex_data = incoming.decode("hex")
    msg = bytearray(hex_data)
    check = 0
    for i in msg:
        check = AddToCRC(i, check)
    return hex(check)

def AddToCRC(b, crc):
    if (b < 0):
        b += 256
    for i in range(8):
        odd = ((b^crc) & 1) == 1
        crc >>= 1
        b >>= 1
        if (odd):
            crc ^= 0x8C # this means crc ^= 140
    return crc

def check(incoming):
    """Returns True if CRC Outcome Is 0xx or 0x0"""
    result = calc(incoming)
    if result == "0x0" or result == "0x00":
        return True
    else:
        return False

def append(incoming):
    """Returns the Incoming message after appending it's CRC CheckSum"""
    result = calc(incoming).split('x')[1].zfill(2)
    return incoming + result

if __name__ == '__main__':

    if not sys.stdin.isatty():
        # there's something in stdin
        msg = sys.stdin.read().strip()
        if msg == "":
            print("No data input. Either provide by stdin or arguments")
            sys.exit(1)
    elif len(sys.argv) > 1:
        msg = sys.argv[1]
    else:
        print("No data input. Either provide by stdin or arguments")
        sys.exit(1)

    try:
        sys.stdout.write(calc(msg))
        sys.exit(0)
    except Exception as err:
        print("An Error Occured: {0}".format(err))
        sys.exit(1)

import crcmod
crc8_func = crcmod.predefined.mkPredefinedCrcFun("crc-8")
crc8_func(b'Hello')

clarkli86, maxim's 8-bit crc calculation is not the same as crcmod's "crc-8"

Looks like crcmod does support Maxim's crc8, though:
http://crcmod.sourceforge.net/crcmod.predefined.html

import crcmod.predefined
crc8 = crcmod.predefined.mkPredefinedCrcFun('crc-8-maxim')
print hex(crc8('\x70\x2b\xbb\xea\x00\x00\x00'))
0xF0

May I suggest :

stream = b'\x02\x1c\xb8\x01\x00\x00\x00'
crc = 0
for c in stream:
    for i in range(0, 8):
        b = (crc & 1) ^ ((( int(c) & (1 << i))) >> i)
        crc = (crc ^ (b * 0x118)) >> 1
print(hex(crc))

Might be usefull for MicroPython
Implemented from : https://www.maximintegrated.com/en/design/technical-documents/app-notes/2/27.html