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Option TCP-RTU factory configures the WattNode® Modbus meter to use the Modbus TCP-RTU protocol (Note: the meter still communicates over RS-485). This allows the use of a low-cost Ethernet serial device adapter (aka Ethernet/RS485 converter) instead of a Modbus TCP/IP gateway (normally required to convert from Modbus RTU to Modbus TCP-RTU).

If you have meters that were ordered without Option TCP-RTU and you need Modbus TCP-RTU protocol, it can be field configured using the ModbusMode (1655) register, which has the following settings:

  • 0 – RTU
  • 1 – TCP-RTU

If you have a meter ordered with Option TCP-RTU and need RTU protocol, it can be overridden or turned off in the field by changing the the ModbusMode register. However, you will need to configure your Modbus master device to use TCP-RTU in order to write a new value to the ModbusMode register.


  • The WattNode Modbus meter with no options defaults to RS-485 communication with RTU protocol, no parity, eight data bits, and one stop bit (N81).
  • Setting all the DIP switches to the OFF (0) position for ten seconds will reset all communications settings to the settings as shipped from the factory. So if you cannot communicate with a meter and suspect that the protocol or a communication setting has been changed in software, you can set all the DIP switches to zero for ten seconds, then change the DIP switches to assign a valid address and baud rate. Then try communicating with the meter.

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