Communication protocol between indoor and outdoor units in minisplit system

Hi, do you have a sample of the protocol between the outside and inside unit of the split air conditioning?
I do not really care about the manufacturer as it is one that is supplied with a 5 wire cable: L1, N, PE, Com1 usually red, comm.2 usually white

I can control the indoor unit using the UART port it does have for this issue, but I would like to see directly what is going on between the indoor and outdoor unit as the indoor unit

Since the indoor unit can read outside temp, I think it is more than just on/off for heating and cooling as the indoor sends outside temperature over its UART port

Has a colleague managed to find out about the 1-wire communication protocol between the inside/outside unit?

xbary wrote:

Has a colleague managed to find out about the 1-wire communication protocol between the inside/outside unit?

I can say from myself that I tried to analyze this protocol and in my case (Haier 1U12BE5ERA) the transmission went over UART 1200, 9N1. To let it go with one cable, the UART is looped, i.e. the external unit transmits on a common line with its receiver and vice versa. That is, each unit gets an echo of what it transmits itself, data from the other unit also flies. This is sent after translation to perhaps 18 V.

What I can say for sure - all possible temperature parameters are sent from the external unit (in my case it was: Discharge temperature, Defrost temperature, and Ambient temperature.

The only thing is that nothing is sent in any human-understandable way.... But, by simulating individual sensors, you can decode which variable is changing. I lacked patience.



Three bytes were responsible for three temperatures. Probably these three:



The mode of operation was also transmitted, I'm sure. Probably also a pile of other parameters.

You need to have a complete clique and logic analyzer - I used Analog Discovery 2, it is suitable for this. Just what to do next... These air conditioners can behave incomprehensibly when they are operational and originally connected, and sending them their own bytes....

I have an idiotic question - this guy here also describes 19 bytes in a message https://kaspars.net/blog/gree-amber-nordic-gwh09yd-s6dba1. Is this the result of using 1200 bps or is there a chance for the protocol to be similar between different manufacturers?