Recent content by sn4p

  1. sn4p

    Modbus connection to Trane Fan&Coil Unit

    4 pin (presumably 4-wire) RS-485 gets jumpered to connect to 2-wire RS-485 by jumpering the (+)'s together and the (-)'s together, for instance Rx- jumpered to Tx-, RX+ jumpered to Tx+. Try swapping at the 2-wire end because some vendors label Plus and minus the opposite of other vendors...
  2. sn4p

    Modbus connection to Trane Fan&Coil Unit

    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...
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    • Replies: 3
    • Forum: Modbus
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