Olin Lathrop wrote:

> I would stay away from IIC, but SPI should be fine with a few basic
> precautions.  2 meters shouldn't be that hard to do at all, assuming the
> other end is not separately grounded.  A few possibilities:

for what matters (and I'd discourage this in the OP's application - I'm 
kind of close to CERN and would not like to see an explosion from here 
:)) ) I've used I2C up to 5-8meters, just lowering pull-ups to 
330-470ohms, lowering speed to some 10-15KHz, and using Cat5E cable.


> 1 - Just hook it up using the existing digital outputs and inputs.  Use a
> separate twisted pair for each of the three digital lines.  This will
> probably work fine most of the time.

exactly, agreed


> 3 - Use redundancy.  Don't believe the answer unless you get the same value
> or close to it twice in a row.

good one too

> 4 - Use differential signalling, with single ended to/from differential
> converters at each end.  There are off the shelf chips that do this.

yep, agreed

> 5 - Put a little PIC at the sensor, then have it send back data wrapped in
> packets with checksums.

agreed as well, IMO if hardware and costs can be accepted, I'd go with 
this and 485 or so.


-- 
Ciao, Dario -- ADPM Synthesis sas -- http://www.adpm.tk
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