Re: serious problems with slimp3 player

> 	There might be a problem with the power supply - if the power supply
> isn't working properly at 220v, it could be overdriving or underdriving
> the circuitry. Is there a 5v regulator on the board? Is that what the
> two large 4-pin units on the back of the player board are?

I've tested the switching supply on 220V - the output is clean (<50mv
ripple). Bill is right though, the board could benefit from additional
decoupling. There's a big cap on the display, near the power connector,
and .1uF caps sprinkled liberally around the digital parts. However, it
could use another large cap at the input, and one at the cs4334.

The 4-pin parts on the back of the board are oscillators, 20MHZ and
14.31818MHZ.

> 	If it does have a 5v regulator, it might be getting too little power,
> but that shouldn't cause the firmware to be _erased_, just inaccessible.

Linear regulators are a bad idea due to the heat they generate. You really
want to use a switching supply for anything over 250mA or so.

> 	You might want to put Dominik's original PIC chip into a known working
> player, to check if it works there. That would rule out a bad chip.

It's definitely happening in the PIC. I've tried putting the corrupted PIC
into another player, and it does not work. I have not yet done a full
inspection of a corrupted chip (by reading the firmware off of it) but
there's a slight possbility that this will give some clues as to
what bits are getting corrupted, and with what data.

> 	The stereo output could have been connected to something that draws too
> much current, and the CS4334 could blow, but that should just cause a
> dead audio out (not a flaky player). However, worst case scenario, if
> something shorted inside the CS4334, that could start frying other
> components and/or the power supply. Unlikely, but tiny logic chips are
> delicate.

I don't think it's possible to damange the DAc that way. Anyway, I really
doubt that this is a power supply issue.

Currently my best guess is that there's some kind of unexpected or
malformed packet which is causing the firmware to crash, and jump off into
the routine which writes configuration changes to the flash. There are
several safeguards around these instructions already, but there may be
some additional sanity checks I can add.

The next thing I'm going to try is sending garbage packets to the player
while pinging it. When the pings quit coming back, you've found a packet
that crashes the player.

Are you guys up late, or early?  :)

Sean


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