Long-cable connection between Picaxe Units

Found at last - what looks like a reliable, flexible, and economical way of linking Picaxe chips over considerable distances of Cat5 cable.

The answer is to use a P82B96 IC at each end of the run:

The P82B96 is available as a DIP8 costing less than a 20x2 in the UK (I used RS online). Using the i2cslow_8 setting, I have managed 300m with just a simple master-slave pair. Adding a second slave (simply teeing off from the two twisted pairs) saw the system fail on a 300m length, but it is fine on a 100m length (I don't have any lengths in between to test with).

Don't forget the pull-up resistors on SCL and SDA on both master and slave (10k worked for me)!

Source of the 12v circuitry is here - see Figure 4

Hope this helps someone.