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Re: [avr-gcc-list] stk 500 dead - how to fix?

From: Joerg Wunsch
Subject: Re: [avr-gcc-list] stk 500 dead - how to fix?
Date: Mon, 8 Aug 2005 23:28:41 +0200 (MET DST)

Reza Naima <address@hidden> wrote:

> I just got an smd rework station, and can swap out the bad uC, but
> i'm wondering - can I just load up the firmware from the website and
> have it work?  Any chance of just reflashing the current chip?  I'm
> not sure what the failure modes of these chips are.

``these chips''?

There are so many of ``these chips'' on an STK500. ;-)

I recently fried mine by a loose power cable that accidentally slipped
under the board.  ISP programming ceased to work then.  It turned out
I killed half of a dual transistor in the target reset logic, as well
as a tiny-logic gate (one gate out of an 74LS14) that amplifies the
crystal clock for the target, plus, I broke one pin of another dual
transistor while searching for the failure. :(

I suggest you first obtain the schematics of the STK500.  They are
available at least on AVRfreaks.net (search hard enough for them).
Then, start analyzing the problem.  If you're luck, you only broke one
of the voltage regulators or such.

If you didn't break the AT90S1200 bootstrap loader, you should be able
to reflash the AT90S8535 main controller chip.  If you broke both of
them, I guess you gotta ask avr at atmel com for help to get the
initial firmware for the bootstrap loader (though it's quite possible
this is a standard AVR910 firmware only).

> And are there any other sensitive ICs that could have died?

Basically any semiconductor on the board could.  To give you an idea,
my failed transistor was next to the main RS-232 connector, the broken
7S14 chip is the 5-pin one beside the `PROG CTRL' header.  Without the
schematics, it would have been impossible to locate them.

cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)

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