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

Charles Bland root at blandranch.net
Thu Jun 26 18:51:39 CDT 2014


Kenneth,

Have you seen this?

https://www.tapr.org/pub_ax25.html

2.2.7 Frame-Check SequenceThe frame-check sequence (FCS) is a sixteen-bit
number calculated by both the sender and receiver of a frame. It is used to
insure that the frame was not corrupted by the medium used to get the frame
from the sender to the receiver. It shall be calculated in accordance with
ISO 3309 (HDLC) Recommendations



On Thu, Jun 26, 2014 at 1:34 PM, Kenneth Finnegan <
kennethfinnegan2007 at gmail.com> wrote:

> Gentlemen,
>
> 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
> http://blog.thelifeofkenneth.com/
>
> _______________________________________________
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> aprssig at tapr.org
> http://www.tapr.org/mailman/listinfo/aprssig
>
>
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