Steve Rapinchuk wrote:
> I'm working on a project for a client which, among other things, 
> includes an interface between a 100 kHz I2C master and an I2C slave 
> separated by 1 km or more. To do this, signals are transmitted 
> optically over a single fiber. Yesterday while testing, we ran it 
> successfully at a distance of 2 km. This got me wondering, what is 
> the "World's Record" for the:
>
> 1. Longest documented standard unbuffered I2C connection (clock and 
> data over copper) running at 100 kHz?
>
> 2. Longest documented buffered I2C connection (either electrical or 
> optical) running at 100 kHz?
>
> Although I've specified 100 kHz, any info you might have at other 
> clock rates would be interesting as well. Are there any other 
> applications out there which would benefit from a long distance I2C 
> solution? (Yes, my client was wondering.)
>
>
> -Steve Rapinchuk 
>
>   
The protocol was clearly designed for the TV motherboards of the 1970s, 
a max length of a
meter or so.

I have a hard time believing anything will work to a km unless it is 
optical fibre, because of
RF noise. I suppose that two RS485 twisted pairs might be made to work, 
but that is NOT
the I2C spec, either.


--Bob Axtell
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