I read I2C is not good for off board communication.

I dunno how long distance is.
But I do see equipments like consumer products using SDA and SCL connected thru ribbons.

My question is, say for like 5 inches apart, is off board I2C communication a problem...I do not need high speed.

 

I read I2C is not good for off board communication.

I dunno how long distance is.
But I do see equipments like consumer products using SDA and SCL connected thru ribbons.

My question is, say for like 5 inches apart, is off board I2C communication a problem...I do not need high speed.

I'm no expert on I2C, but I can't see 5 inches being a big problem, provided the EMC environment isn't too bad and provided also you've got good grounding between the two boards. If I were doing it I'd probably do it with a 6-conductor ribbon configured GND-SDA-GND-GND-SCL-GND. Or maybe with a few extra grounds for good measure...

 

I had lcd display that was a couple of feet away from arduino board that we sent data to display using a couple of wires, not even a ribbon, and it worked fine. 5" should be fine.

 

Yaa. All are saying be good to ground..be good to ground.!!
I do not see why "GND-SDA-GND-GND-SCL-GND." won't be good to ground.
Plus The PSU wire will be running separate and two boards will have a ground plane.

 

I made a fixture composed of 1 master and 10 slaves in a 12 x 18 box. The master controlled and powered the slaves over a 4 conductor ribbon cable.

Everything worked just fine, though I did allow for bad data I would require, and the I2C was run a bit slow (100 k perhaps?).