Re: [avr-chat] ATXmega and usersig

[Alexander Krause]

Hi Bob,

thanks for your hint.

The production serial consists of the wafer number, y and x coordinates
and is far to long for my purpose. I'd like to fit the serial into a
16bit ModBus register which currently works pretty well with my two
usersig-bytes.

> Note this comment from the above URL:
> 
>    (void) SP_ReadCalibrationByte( offsetof( NVM_PROD_SIGNATURES_t,
> LOTNUM0 ) ); /* First read after reset or possibly Power Up returns
> zero, so read then toss this value */
> 
> I reported that issue to Atmel when the parts first came out.  They
> said they could not reproduce it.
> A few others have seen the same thing over the years.
Thanks, I already use the code from Atmels app-note and as far as
 I can remember I'm also skipping the first read.

> So try reading your USER_SIG value twice, see if you get what you
> expect on the second try.
> All reads after the very first one, after a reset, work just fine.
Good point. Guess I'll give it another try.

Anyway, I read that there also is an erase command for the usersig and
avrdude does not implement any option for it. I'll try the current AVR
Studio and will see if I can somehow change my usersig in there.

I'll send my findings tomorrow.

Regards,
  Alex