RS232 Connection to ComfoAir 350 / wrong adapter?

Hello All,

I’m working on the connection to my ComfoAir 350 (RJ45 Port with RS232). I started with an USB to RJ45 cable with Ftdi-Chip. Well, as a result the USB plug get very hot and the ComfoAir stoped working. After unplugging the RJ45 it was fine again. I have checkt cable and port:

RJ45 Port:
Pin 1: 12V
Pin 2: RS232 RX ComfoAir
Pin 3: RS232 TX ComfoAir
Pin 4: RA7 / PIC18 (function unknown)
Pin 5: RB2 / PIC18 (function unknown)
Pin 6: RA6 / PIC18 (function unknown)
Pin 7: RB1 / PIC18 (function unknown)
Pin 8: GND

FTDI Cable:
Pin 1: RTS
Pin 2: DTR
Pin 3: TXD
Pin 4: GND
Pin 5: GND
Pin 6: RXD
Pin 7: DSR
Pin 8: CTS

Looks like it doen’t match and the 12V cause the plug to geht hot.

I have found an other USB Stick. It’s USB to TTL with a CP2102 chip and this pinout:
Pin 1: 3,3V
Pin 2: TXD
Pin 3: RXD
Pin 4: GND
Pin 5: +5V

Is that someting i can work with, or do I need other hardware?


REAL RS232 is : -3V to -15V is “1”, +3V to +15V is “0”
On the other hand, USB to TTL is 0V is “0”, 5V is “1” (sometimes 3.3V is “1”)

Ensure which sort of serial interface is used in ComfoAir350.

All you are really interested in is connecting three wires; RX, TX, GND to TX, RX, GND on the other device

Thanks for the replys. I removed the coat from the USB RS232 Adapter and connected RX, TX and GND directly (RX to TXD / TX to RXD)

Response in the log is always “null”.

Maybe the adapter was damaged when he was connected the first time with the comfoair and get the 12V from Pin 1. I have ordered a new USB to RS232 (D-SUB) and a adapter from RJ45 to D-Sub where I can configure the pin’s. Hope I will get in on wednesday.