Re: How to add I2C device disable preamble?

As Bob Paddock wrote:

> >preinit = "reset low; mosi high; sck high; wait 200;\
> >           sck low; wait 100; mosi low; wait 10; mosi high; \
> >          ...";

> I'll have to look to see what the exact I2C sequence
> would have to be.  Also it changes between manufactures
> of the Accelerometers.

That's why I would never want to have something like this tied
directly into avrdude, but rather in a user's startup script.

> >For a completely different route, couldn't you build one of those
> >ISP programmers that implement STK500 protocol but use their own
> >micro to run the bit-banging?

> I had not thought of that, but that would mean more hardware
> to maintain.

Well, you have to maintain the programmer hardware anyway, either the
40-cent-ISP-one (where the host computers with a parallel port are
becoming a bottleneck, or you have to invest in additional hardware
much beyond 40 cents for a separate parallel port), or the standalone
ISP one.

As for Matthias Weißer's USBisp, you can at least buy the PCBs from
him if you desire.  I think there are other vendors who would sell you
a complete solution but nevertheless give you an opensource firmware
along.

To me, that path would be the most promising one at least (provided
the I²C-disable-by-SPI proves to work at all).
-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

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