Re: [avr-libc-dev] XMEGA hardware CRC calculation

[Bob Paddock]

>> See this thread on AVRFreaks for some of the needed code for the
>> external program.
>> http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=80405
>>
> Did you get that code from Atmel?

I make reference to Atmel supplying some broken code some place, that
was the basses for that message.
I sent what I fixed back into them, which might be what they are
sending out now.

 It is basically the same code I get from Atmel support, this is the
PC version taking an octet stream and the length of data to compute as
input:

Thank you.

> app section CRC) we end with an odd number of bytes to compute. Do we need to 
> add a byte valued to 0 at the end?

Probably.

> I can't understand how they process 16 bits at a time without doing a loop 
> through all bits or using a precomputed table.

I would suspect at the hardware level it is shift registers.

> I'm not a math guru but this seems to broke the mathematical principles at 
> the base of CRC calculations.

Which is what I suspect.

> If you can test this and find out what's wrong and maybe make it works,
> it would be a very nice thing and perhaps we could add the routine to
> the avr-libc help to make it available to everyone.

Real Soon Now...

>> I was referring to die revision J.  That is what Atmel said they would
>> fix the CRC Rage problem in.
>>
> That makes my laugh! They are stuck on rev.H with plenty of errors to
> fix for two years and they expect to solve the CRC problem not in the
> next revision but in the one after? When they expect to release the J
> revision, in 2013 or later? Come on, I have firmwares full of patches
> and tricks to overcome XMEGA faults!

It is common to skip the letter "I" because it looks like the number
"1". I do agree with you.