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Re: [avr-libc-dev] [bug #37901] CRC-CCITT calculation incorrect

From: mojo
Subject: Re: [avr-libc-dev] [bug #37901] CRC-CCITT calculation incorrect
Date: Tue, 11 Dec 2012 15:07:02 +0000

If you are interested I have working code that implements the IEEE
802.3 CRC-32 and is compatible with the XMEGA CRC generator. I also
have code that generates the weird CRCs the XMEGA produces when it
calculates the checksum of the flash memory regions, both for AVR and
32 bit processors (so that firmware updaters can compare notes with
the XMEGA).

Paul aka MoJo

On 11 December 2012 14:57, Weddington, Eric <address@hidden> wrote:
> Joerg, do you have any idea how much this function is actually used?
> I might be open to doing some renaming, if the pain that it would cause 
> existing users is minimal.
> I think it would be a good idea to support xmega users too.
> Eric
>> -----Original Message-----
>> From: address@hidden
>> [mailto:address@hidden On
>> Behalf Of mojo
>> Sent: Tuesday, December 11, 2012 7:29 AM
>> To: Joerg Wunsch; mojo; address@hidden
>> Subject: [avr-libc-dev] [bug #37901] CRC-CCITT calculation incorrect
>> Follow-up Comment #2, bug #37901 (project avr-libc):
>> Okay, but in that case I think that needs to be made clear.
>> The standard CCITT CRC should produce an endian and bit-order independent
>> result that is compatible with other implementations. I understand that it
>> is
>> designed to be compatible with the IRDA standard, but it appears to be a
>> mistake on their part or at least the result of confusion over which
>> version
>> people are usually referring to by that name.
>> As I pointed out, the biggest issue for me is that it is incompatible with
>> the
>> XMEGA CRC module's implementation. Renaming the functions is probably out
>> of
>> the question now, but the documentation should at least be amended to make
>> it
>> clear which one you might want to use. There are lots of threads on AVR
>> Freaks
>> from confused programmers wondering why it doesn't work.
>>     _______________________________________________________
>> Reply to this item at:
>>   <http://savannah.nongnu.org/bugs/?37901>
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