using cat5 cable for signals and power?

[danrogers]

Hi all, I will be using some cat5 (probably about 2-3 meters) to connect a remote ST7735 based TFT over SPI. There will also be 1 analog signal coming back from the remote unit (a potentiometer).

I'm not sure which signals to connect to combine in twisted pairs, should I connect 5v and ground in the same pair, or split them? Where should I connect the analog signal to avoid as much noise as possible?

The signals are (x8):
Power: 5v, gnd
TFT: clk, mosi, cs, rs, dc
Pot: 0-5V

Many thanks!

 

[ronsimpson]

There are many options.
CLK has the most noise issues. You could pair it with ground.
MOSI is next for noise issues. You could pair it with 5V. (supply should be coupled to ground with capacitors so it is much like ground)
I can not guess what noise problems you will have with POT. You could pair it with what ever signal has the least amount of edges. Maybe DC.
I think you can pair (CS, RS or DC)

Just my thoughts.

 

[danrogers]

Ron, thanks that is exactly the information I was after, sounds logical to me. I will give it a go,

Thanks

 

[ronsimpson]

If you have noise problems on POT add a resistor and capacitor (low pass filter) to clean up some noise.

 

[crutschow]

If you are concerned about noise conducting into the other lines then you could use differential pairs, particularly for high frequency digital signals, by using differential line drivers and receivers.