I'm trying to automate the AC in my building. I've found that the indoor units have a Modbus (4 pin) connector (see attachment). I assume all pins are signal pins (full duplex TX+, TX-, RX+, RX-) since there is no voltage on the pins. Under the connector it says COM4. I've done some digging and Trane supposedly uses a proprietary protocol called COMM4 (note two Ms).
I found an online manual for an identical unit here:
https://www.manualslib.com/manual/1948585/CooperAndhunter-Ch-Irt05nm.html?page=24#manual
It says it is using Modbus 9600 baud (I'm assuming 8N1). I'm using an Arduino with a RS485 board (5V). However I can't get any response from my Modbus commands. I've tried every combination of the pins (full/half duplex). I've set the unit's slave address and configured it to long distance control which should enable Modbus...
I don't know if it actually use Modbus or it's own COMM4 protocol or if I'm using the wrong voltage (maybe 10V?) or something else.
Any help appreciated.
I found an online manual for an identical unit here:
https://www.manualslib.com/manual/1948585/CooperAndhunter-Ch-Irt05nm.html?page=24#manual
It says it is using Modbus 9600 baud (I'm assuming 8N1). I'm using an Arduino with a RS485 board (5V). However I can't get any response from my Modbus commands. I've tried every combination of the pins (full/half duplex). I've set the unit's slave address and configured it to long distance control which should enable Modbus...
I don't know if it actually use Modbus or it's own COMM4 protocol or if I'm using the wrong voltage (maybe 10V?) or something else.
Any help appreciated.
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