Panasonic A/C communication protocol

[Josh6899]

Hi all, i'm very new with electronics, looking to get a better understanding.
I work as a HVACR tech and I've been looking into making an Arduino thermostat to use mainly on Panasonic's ducted inverter A/C.

The issue i'm facing is that i don't know how the controller talks to the indoor PCB, there's 2 wires and they connect to terminals "R1, R2" which is between 12v-16v DC. I understand that it sends 12v DC to power the thermostat but is there some kind of Pulse width modulation to communicate with the system ?

If we can figure out how the RC communicates with the PCB then it should be possible to make an Arduino communicate also.

I've included some data sheets.

Any suggestions on this will be greatly appreciated

 

[Bluejets]

Probably thermistors but just how Panasonic decide to interface that with the main units would almost be a company secret I would assume.
Could be any of a number of ways.

 

[Josh6899]

There's a company called "izone" which make a smart controller system and they have an interface module that communicates between the main unit and the "izone system" so it seems the interface communication protocol can be accessed and that's basically what I'm after!!
As for the thermistors, you're correct but they're all connect to the indoor unit PCB and the indoor unit PCB is then responsible for calling for corrective action based off of the thermistors and what the controller is calling for

 

[Bluejets]

No argument there but finding just what that is could be likened to guessing how many jellybeans in a jar.
These days things tend to be microcontroller based and digital sensor output for accuracy so aside from perhaps I2C or whatever, then there remains the programming.
Good luck at reverse engineering any compiled code therein.

 

[shumifan50]

I would imagine that it would be easier to scrap the pcbs in the units and build your own from scratch as it might prove to be much easier than trying to reverse engineer the existing implementation.