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I2C bus length

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That's the R&D spirit, but not a big surprise since I2C is single ended with respect to a common ground. One of the problems with long cables is that ground at one end may be much different from ground at the other end. Longer cables make the problem worse. Differential signals on twisted pairs have a higher tolerance for ground differences. One thing you can do is use a smaller guage(larger diameter) for the ground wire.

A good start for a long I2C cable would be an 18 ga. ground wire and 2 -22 ga. signal wires.

Industrial networks like DeviceNet can do 125kbaud at 500 Meters with or without opto-isolators. That physical layer uses quasi-differential signaling with respect to a common ground and can tolerate 5V common mode ground difference between the ends of the cable. The standard transceiver is the Philips PCA82C251.


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Why resurrect a thread that is 4 years old.

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