I have made some tests with a temperature sensor tmp102 connected with 1m long cables and it works great. Now I am wondering if I can use a 10m long cable and if yes, what type of cable shall I use? I've read that i2c bus was originaly designed for shord distance.

  • 10m is pushing it, but there's no harm in trying. You might improve things by reducing the value of the pull-up resistors. – Ian Howson May 17 '13 at 7:27

This should help you: AN10658 Sending I2C-bus signals via long communications cables

If possible you should use a cable with the lowest capacitance, maybe Cat5 cable or something closer. Shielding won't hurt either.

The maximum I2C cable capacitance is limited to 500pf, a cat5 cable has the capacitance of 50pf/meter. So, basically, for a 10m cable you will be fine if you use 100kHz standard transmission mode. For longer cables you might need to lower your transmission speed, people on the net talk about 100m length clocked at 500Hz.

  • Thks, do you think I can use ethernet cable? – Penbeuz May 15 '13 at 12:11
  • Or even telephone cable? – Penbeuz May 15 '13 at 12:46
  • @penbeuz I'd prefer ethernet, but even the phone cable might work. Sorry, I haven't tested this personally. – lenik May 15 '13 at 15:56

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