[OT] I2C over Cat5
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tkerby

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This isnt entirely headphone related but it may be something that people here have tried. I'm trying to get a camera chipset to function over a 2m length of Cat5 cable with the aim of working with longer lengths. At present I have the following setuo

Pair 1 - LVDS Video data (differential signal)
Pair 2 - LVDS Clock signal (differential signal)
Pair 3 - I2C SCA and SCL lines
Pair 4 - Camera Reset (active low) and GND

What I am finding is there is a large amount of crosstalk in the I2C and small capacitive loading effects. I'm using 200kHz I2C with standard 4K7 Pullups.

This could potentially be used in an audio setup with 2 differential audio channels and some control signals, hence asking here. Anyone have any better ideas for the connection. My thoughts so far are

Split I2C over pair three and four - that way one is coupled with ground (may have more capacitive loading - bad) and one with a normally positive signal. The positive signal would be fine as I2C is pulled hard to ground so a coupling to the +VE supply is unlikely to cause a problem (its already coupled through a resistor). The ground coupling worries me slightly more as it will limit the length of comms as I2C only survives 400pf line capacitance.

I'm also concerned as I have been told that there is a tight twist and loose twist. Does anyone know which cables are which as I2C is very much edge dependent and i wouldnt want to have one signal going down a longer pair than the others.
 
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