This post originated from an RSS feed registered with Python Buzz by Phillip Pearson. Original Post: Generating Motorola S19 checksums in Python Feed Title: Second p0st Feed URL: http://www.myelin.co.nz/post/rss.xml Feed Description: Tech notes and web hackery from the guy that brought you bzero, Python Community Server, the Blogging Ecosystem and the Internet Topic Exchange Latest Python Buzz Posts Latest Python Buzz Posts by Phillip Pearson Latest Posts From Second p0st

A friend just popped up on MSN and asked me how to generate S19 checksums in Python. It's a pretty trivial bit of code, but I know I'll want it again, or maybe someone is out there googling for a way to do it, so here we go:

def s19_checksum(line):
    length = eval("0x" + line[2:4])
    bytes = [eval('0x' + line[i*2:i*2+2]) for i in range(1, length+1)]
    return ~reduce((lambda a,b: a+b), bytes) & 0xff

for s in ('S1130170707172737475767778797A7B7C7D7E7F03',
 'S111FE7B59597B0173F6014A7B0146B7573093',
 'S106FE891B823D98',
 'S109F8020107DF01BA0D6C',):
    print "* checksumming %s" % s
    print "checksum: %s (compare with %s)" % (hex(s19_checksum(s)), s[-2:])

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