TCA9517DR on I2C for long distance wiring with high capacitance bus

by VirtApp   Last Updated August 01, 2020 14:25 PM

I have a CAT6 cable that was used for old temperature sensors that works with 5V I2C at 25/30 meters from the main MCU with cable pairs that brings VCC-GND-SCL-SDA.

Here is the schematic:

enter image description here

I've tried using an ESP32 with I2C bus speed of 100kHz with another PCA9306 at the Gateway end of the cable but it works for maximum 5 meters (and with many errors...)

The cable has a capacitance of 56pf/m, so 30 meters are 1680pf in total, higher than the maximum I2C limit of 400pf.

I know that i2c should not be used outside pcb, etc, etc..i can't change/add nothing more than the main gateway that collects those sensors data.

Now i'm looking for a solution for that: maybe i can use a repeater and level translator like the TCA9517DR and lower the pullup resistor on A-Side in order to fight the cable capacitance?

In any case, i wish have some useful advices about which parts i can use and how i can solve this issue.



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