>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 20 May 2005 06:13
>To: Microcontroller discussion list - Public.
>Subject: Re: [PIC]: Simple PIC-to-PIC communications options?
>
>
>On Fri, 2005-05-20 at 00:24 -0400, Matthew Miller wrote:
>> 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.
>
>I agree I2C may not be the best choice, but it's certainly not 
>limited to small distances.
>
>My house monitoring network is I2C, and the farthest station 
>is about 20 meters (60 feet). As long as you do things slow 
>enough I2C is definitely possible to get working.
>
>That said, even going to a "multidrop" rs232 would be far 
>better, with rs485 and CAN being much preferred options. TTYL

Philips has an app-note on using I2C over distances of 1km using special
buffers, so it is possible.  However, wether it's worth the bother when
there are other widely used comms standards that work out of the box for
the distances the OP is interested in is debatable.

Regards

Mike

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