I2C optimal wiring twisted pairs

Projects Networking, Protocols, and Devices
1

Hi,

I have written some code for a humidity control project: based on readings from different sensors, I will control a ventilation system.
The basic setup is: 4xSHT31 connected via TCA9548A I2C Mux.
As some sensors will be pretty far away (further than the advised 2-3m, max 5m away if tests show that that could work) from the TCA9548A, I want to have the wiring as ideal as possible to minimize interference.

I will be using 'alarm cable' (edit: or cat6 utp) which consists of two twisted pairs.
What's the best way to group the cables?

  • VCC+GND (pair 1), SCL+SDA (pair 2)
  • VCC+SCL (pair 1), GND+SDA (pair 2)
  • VCC+SDA (pair 1), GND+SCL (pair 2)

Or is this not relevant at all? If so why ... and what's could be done otherwise to have potential better/more reliable signals.

Kind regards,
Maarten

2

Hi

Separate VCC from 3 other wires (but actually you need to test this ... )
Also there is some Application Note for I2C communication on the internet ...

UM10204.pdf (1.33 MB)

AN10658.pdf (423 KB)

3

One pair should be SDA + Gnd and another pair should be SCL + Gnd.

If you need to include power in the cable then I suggest a third pair with Vcc and Gnd

...R

4

Thanks guys! Clear! Karma+

5

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