The mode switch is on RS485. Otherwise not exciting, the wiring is RX+ on board to the + terminal on, and RX- on board to the - terminal.

Does wire gauge matter, i'm using 18G shielded, whereas the outdoor unit gets 16G, does this matter? its unclear if 16G wire would fit in the terminal connections of the serial tap. I'll try what your saying and report back.

However, with these settings and without the the modbus analyzer i see the occasional framing error.

I'm trying to sniff on the communication between the my heat pumps master board (shown in photo) and its outdoor unit.

I've added shielded 18/2 and followed a route in the box to avoid the line voltage wires as much as possible (also following manufacturers route).

By trial and error i worked out these settings which avoid regular FRAMING, PARITY and BREAK errors.

I'd like some advice on why I may be seeing continued error and how to use this advanced analyzer to work out the correct settings.

Assuming i can parse this modbus correctly i'd then like to have a persistent process for dumping the registers of this device to home assistant.