> So another test is to wait for the problem to happen again,
> then load the card into a computer and create a tiny file
> unrelated to the application, then see if that fixes the problem
> for the moment.

I started a test at 9:15pm and expected the card to fail about
18 hours later, as it had done twice before.

18 hours came and went. So did 24. And 30.

I've never been so disappointed to see something working
properly !!!

Then finally ......

I re-powered the circuit a few times and it stopped reading after
a short while each time, so that's still the same

However, I did notice an occassional click in the sound and on
the scope saw that the dsPIC DAC seems to do a full excursion
to make the click, as though there's a byte of 0xFFFF data. The
proper signal is ~ 0.1Vp-p (centred around mid-point data of
0x8000), the click is ~0.8Vp-p, or 0.4V above and below

Uploading the card file to the PC and comparing with the original
showed no difference (I verified that fc works by comparing to
another file. Mismatches galore). The card controller must be the
source of the bad data. Not every instance of playing that file and
sometimes the click is noticeably longer (although still a fraction
of a second), maybe a small few 0xFFFF bytes

Unfortunately because the card stopped working during the night
I didn't get to hear whether the click appeared before it failed. That
was partly the point of trying to get the failure to happen when I
was at the desk mid-afternoon. If I actually witnessed the failure
it might have been possible to determine if it was a 32768 count
or something like that. The card going for nearly twice as long
has blown that theory

So then I wrote another small file to the card. This doesn't seem
to have made a difference. The card still fails shortly after power-
up and the sound still occassionally has a click

Back to the drawing board

Joe


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