RS485 Input Voltage Levels

[Sparky84]

Hello,

I am a little rusty on RS485, and I am unsure if it will read a (0-5V) PPS input signal.  I have a spare RS485 input and I thought this would be a simple way to read a (0-5V) PPS signal into a 3V3 microcontroller.  So essentially the signal path would be as below:

PPS (0-5V) -> RS485 -> UART -> Microcontroller

I think this should work, but I just needed a second opinion before I get the soldering iron out 

Many thanks,
Sparky84

[David Hess]

A RS-485 input should read a 0 to 5 volt digital signal just fine.  A DC input at the other RS-485 input sets the threshold and the RS-485 receiver then operates as a comparator.

[Doctorandus_P]

RS485 is a differential signal, and you always have to use the two wires to get the voltage difference. But you can indeed use a DC bias voltage on one of the wires and then use the RS485 transceiver as a comparator.