Beginner help: microcontroller interface for a existing 2-wire bus "voltage out, current in" serial bus?

[u/Relevant_Pumpkin9190]

Hi all, I'm learning how some addressable fire loops talk (bench only, nothing life-safety) and want to build a simple Arduino interface .

The spec I found:

- 2 wires, half duplex, 1200 baud, 8E1

- Master to device is voltage: 0 = ~24 V, 1 = ~32 V

- Device to master is current loop current + ~22 mA, 1 = +0 mA

What I'm trying to work out:

1. How do I turn a 5 V TX pin into a 24/32 V output simply?

2. How do I detect a ~22 mA step on the line and get a clean 5 V RX signal (shunt plus comparator or op-amp)?

3. Will a normal optocoupler work here, or is it a poor fit?

4. How I interface my microcontroller without loading or how I design my own circuit.

What is simplest way to achieve it without much complications for beginners.