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

Charles Bland root at blandranch.net
Thu Jun 26 19:56:42 EDT 2014


This looks more helpful....



On Thu, Jun 26, 2014 at 4:51 PM, Charles Bland <root at blandranch.net> wrote:

> 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/
>> _______________________________________________
>> aprssig mailing list
>> aprssig at tapr.org
>> http://www.tapr.org/mailman/listinfo/aprssig
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