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I2C communication between MCU and sensor with few meters distance

Andreas Hansen
Intellectual 410 points
Other Parts Discussed in Thread: P82B96, TCA9617B

Hi,

In short, what I try to achieve is to connect a sensor to a MCU via I2C where the distance between the two is in the range 2-3 meters. I want to do this in the cheapest and simplest way i.e. with as little added hardware as possible. I'm considering the approach illustrated in the attached image where I both feed the sensor with power and SDA/SCL wires in a single cable. The sensor draws 1.25 mA during conversion. The only component that is put at the sensor-side is a decoupling capacitor of 100 nF. At the MCU-side I intend to place two pull-up resistors of 10k.

I'm aware that I2C is made for inter-circuit communication (probably with distances in the cm-range), but how far is it possible to stretch the distance without facing too many issues due to noise and too much capacitance caused by the long wires. I'm not a very experienced hardware designer (which my circuit might show) so I would like to hear your recommendations and experiences with this.

Best Regards,
Andreas

  • 0
    TI__Mastermind 23116 points

    Hello Andreas,

    I have a few questions for you. 

    1)  What data rates are you trying to achieve? 

    2)  Do you have power constraints?  Is it a battery application?

    3)  What is the capacitance of the cable you are using?  It is usually specified in pF/ft.

    If you don't have power constraints then a good option is the P82B96.

    You might be able to use another buffer like the TCA9617B if the capacitance on the cables isn't to much. 

    -Francis Houde