Hi,

On Thu, May 19, 2005 at 02:26:31PM -0500, PicDude wrote:
>
> The issue though, is that I2C has a limited distance, though I understand that 
> at lower speeds, I can get more distance.  But how much?  I have yet to learn 
> the specifics of I2C, including the various speeds available, but at a high 
> level, would a couple hundred feet reliably be possible for my snail-like 
> data-rate?

I doubt that I2C will work at those distances. The main problems will be
noise, and the capacitance of the lines (I don't have the I2C spec. handy so
I can't tell you what the max capacitance is.) Don't expect I2C to work for
more that a couple of meters. I have seen it work at upto three meters
before.

Olin's suggestion of using the CAN bus is a good one. I've only read about
it, but it seems to do what you want. Myself, I would use RS-485 since I'm
familiar with it. If you go the RS-485 route, look at the ltc1482
transceiver chip. It seems to be about the only transceiver that has a
carrier detect function; this simplifies things a great deal.

Also, if you're only interested in half-duplex you only need one twisted
pair, but this might not matter much seeing how cheap cat-5 cable is
compared to almost any other type.

Take care, Matthew.

-- 
"This is not a scientific issue, it's a political issue," he said.
"There isn't a scientific issue about the validity of evolution. The
only issue is whether schoolchildren will learn real science or not."
          -- Adrian Melott
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