[aprssig] Trying to Specify the CRC-16-CCITT FCS

Kenneth Finnegan kennethfinnegan2007 at gmail.com
Thu Jun 26 16:34:59 EDT 2014


I've been working on trying to specify the frame check sum we use for
Bell 202/HDLC for my thesis. Do we really not have some kind of spec
document like for AX.25 or APRS for layer 1? I've been able to find a
few disjoint articles on the topic, and have been working out of ITU
V.23 and V.42, but the checksum calculation has really got me stumped.

Does anyone have a known-good code snippet that generates the correct
CRC given a complete frame? Attached is what I have working off of a
few examples online but they all seem to generate different results,
particularly for empty sets... The endianess is a total mess, so which
byte gets sent first?

Attached: http://i.imgur.com/vfojzUB.png
Kenneth Finnegan
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