Distance between devices when using I2C protocol on wire?

WBA Consulting

I am looking at a device that uses standard I2C communication but won't have a breakout board for it for a couple weeks. I have found a few different things on the internet, but nothing concrete in regards to real life experience with non-trace distance using I2C. What I mean by non-trace, is how far has someone communicated using I2C across wires? From what I have found so far, 8" is the farthest. I am hoping for 16".

thanks

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010

Mike Green

You'll probably find the best information in some application notes from Philips, now NXP. You should be able to find some links by going to their website and the page introducing I2C. I vaguely remember one that discussed recommendations for various distances, particularly where to put pullups and what values to use.

Timmoore

I have used 12-20" before without problem.

Erik Friesen

I have gone 10 feet using a temp sensor and telephone wire. The power has to be on the inside wires or it won't work. It is not ideal however, and there are occasional errors. Crosstalk in the wires is a big killer with i2c.

T Chap

I use I2C with unshielded ribbon cable on projects over 12' everyday no problem.

WBA Consulting

Thanks for the feedback, that's what I was hoping to hear. I'll have PCBs soon and will get to try this out later this month. The project will be a well documented and end up in the completed projects forum or the customer applications section on the website.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010