Hi Per,

I've done a house heating control application, where I used the I2C-bus as THE bus between all inputs/outputs. 2x PCF8574 for in/out (opto and relais) and in total three DS1621 for temperature reading. The total bus length was around 5 meters. I used a slow clock of about 1kHz.

It worked fine, apart from the unpleasant 'feature' of the DS1621 to hang up every so often. I was told by a DALLAS engineer, that this is a known bug, and you better use the DS1631 instead.

Back to robustness: this is mainly a matter of the driver software. If the acknowledge is checked, and the software reacts on wrong Acknowledge, then the bus is ok for even much longer distances, see:

http://www.semiconductors.philips.com/buses/i2c/

The specifications tell you how to dimension the series resistor to avoid latch-up. Then, ESD should be no problem.

Have fun

Juergen