I have a Panasonic air conditioner that has a header on the mainboard that various optional (expensive) addon communications modules can connect into eg wifi

The unit is a Panasonic Split system from the CU/CSZ20TKR range (however this connector is common across many of the panasonic series)

I am wanting to see if I can connect to this port and control it over serial or similar once I determine what protocol it is using. RS232?, RS485? I have been trying to determine what protocol this port uses to communicate with the addon modules that can be plugged into it and what the correct connections are. Once I have determined the correct pins and protocol I should be able to write a script that will do the communication.

I have done some research and probing with multimeter (I don't have an oscilloscope currently) and located a circuit diagram for the header on the mainboard,

What i have determined so far:

  • Pin 1 5v
  • Pin 2 5v
  • Pin 3 5v
  • Pin 4 12v
  • Pin 5 Gnd

Circuit diagram of the port

Some of the modules available to plug into this port are:

  • You'd have a lot more luck if you had one of the options and could plug it in while watching with a scope or a cheap logic analyzer (be mindful of course of making any electrical connection to line powered appliances - you don't know that the low voltage internals are not riding on lethal mains voltage!). The two signals with the 10K pullups could be an I2C bus but the PAW-SERVER doc implies they are a distinct transmit and receive. Maybe you'll be lucky and those, or the one with no components will see some "is anything there" polling during startup. Apr 12, 2019 at 6:03
  • Thanks for the advice, I have a logic analyzer on order. It would be great if I could get one of the devices, but they are out of my budget for now.
    – Andrew B.
    Apr 12, 2019 at 11:56
  • Not sure if this helps, I have received the cheap logic analyzer and attached to the 3 5v lines. There does appear to be something being output when the device is powered on and also continuously while the device is on and in standby i.imgur.com/Pmi1rC3.png
    – Andrew B.
    Apr 15, 2019 at 21:16

1 Answer 1


I think the pinout is the following according to Server Back-Up PC Board manual:

enter image description here

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