> I'm trying to run a remote I2C temp sensor over phone
> cable 50m away into a PIC. It needs to be very reliable and cheap.
>
> My first assumptions are: Run slow out of the PIC since I can
> control the bit rate and therefore reduce effect of slew due to cable
> capacitance.

        That's a good start, but remember you are dealing with a pretty nasty
transmission line, you'll have alot of reflection going on. I run about a
20m length using standard telephone cable. It works OK and is quite
reliable. What I have done is I read each device 10 times, drop the lowest
and highest result, and average the rest (it is also a temp sensor, the NS
LM75 in my case). Before I allow the result I check the range, if it is more
than a few degrees I try again. It works and seems very stable although I
don't know how many times it has had to retry. Good luck and let us know how
it turns out! :) TTYL

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