Re: [avr-gcc-list] Homebrew ICE?

[Erik Christiansen]

On Mon, Aug 11, 2003 at 09:27:26PM +0200, Joerg Wunsch wrote:
> I'm even willing to make my design publically available, but i have to
> re-edit the schematics, and re-route the board for this to be useful.
> Of course, the prototype finally did experience some minor mistakes,
> and i'd also like to optionally add an 78L05 for the power supply.

   If your schematics import into Eagle, I'd be tempted to help with
   implementing the intended improvements, and have a couple of boards
   made. But I know that I can't give a lot of time, either, for the
   next few months, so it would be slow going.

   Does it need some additional software between it and gdb?

> I'm not sure about the legal situation though: as long as we have to
> rely on Atmel's firmware, it's sort of a grey zone.  I'd prefer it to
> have an opensource firmware for it, but currently don't have the
> resources to donate much time to the FreeICE project myself.

   Would that depend on the circumstances under which the Atmel firmware
   has been obtained? 

> the biggest problem in case2000's simple recipe is the
> missing level shifters.  The Atmel level shifters are ingenious (for
> example, they work with a target Vcc less or above the ICE's Vcc), but
> they require a lot of ``chicken food'', and obviously, in order to be
> able to publish my design at all, i didn't want to copy their
> circuitry.  So i redesigned it using some 74HC4050 etc. buffers.

> Also, the original design does a lot of protection on the JTAG side
> which is missing in this simple design, so if you accidentally drop a
> mains power wire onto your target, you'll for sure also explode your
> JTAG ICE.

   I don't suppose a couple of really fast optocouplers would provide
   the required data rate, while solving both the level and isolation
   issues? (I should check up on developments on that front.)

Regards,
Erik