ihex crc recalculatorCalculates the checksums of lines in an ihex/intel hex file. Useful for patching a hex file.

ihexcrc.py

#!/usr/bin/env python
#
# Intel HEX file CRC recalculator
#  ihexcrc.py FILEWITHDAMAGEDCRC.HEX > NEWFILE.HEX
#
# See http://goodfet.sourceforge.net/dist/intelhex.py
# for a more elaborate version
#
from binascii import hexlify, unhexlify
import sys

if (len(sys.argv)) != 2:
    print("Need IHEX file name as argument")
    exit(1)

for s in open(sys.argv[1], 'r').readlines():
    s = s.rstrip('\r\n')
    
    if not s:
         next         # empty line

    if s[0] == ':':
        try:   
            bin = bytearray(bytes.fromhex(s[1:]))
        except TypeError:
            pass

        length = len(bin)
        if length < 5:
            raise RuntimeError
    else:
        raise RuntimeError

    record_length = bin[0]
    if length == (5 + record_length):
        # w/ crc
        oldcrc = bin.pop()
    elif length == (4 + record_length):
        # w/o crc
        oldcrc = 0
    else:
        raise RuntimeError

    crc = (-sum(bin)) & 0x0FF
    bin.append(crc)
    print(':' + bin.hex().upper())