AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Steve Hodge" <steve@...> wrote:
>
> Thanks for everyone's input.   It's always good to get confirmation!   I'll
> use one pair for SDA+GND and another for SCL+GND.  Or I may substitute V+
> for one GND.

working in vehicle electronics (trains) I always cringe when I see people going off board with a bus that was initially invented to be a simple connection between IC on the same PCB (Inter-IC bus). In a train with it's bursts and surges in the kV range, it berely works on board and I would never even try it "long range".

Sure, in most (hobby) applications it works, but so does towing a car with a schoestring...

> I have other reasons for wanting to use Cat5:  shielding, quick & easy
> connect/disconnect, relatively cheap and easy to make up cables, and for my
> situation cables that are flexible and easy to run convoluted paths is very
> important.   I also have other uses for the remaining conductors in "RJ45"
> cable, so that, plus shielding, is the reason I'm not just using "RJ11" or
> "RJ12" modular cable (I've never been able to find such cable that is
> shielded).

So since you already have a connection made for differential transmission - why not use it just for that? Two RS422/485 trnasceivers aren't that expensive and e.g. a Tiny26 on the receiver side won't even cost more than your I2C Port extender.

Greetings from Berlin, Germany,
Stefan