Troubleshooting tips for Modbus RTU

This topic is to help you identifying error on your modbus setup if it does not work properly
Please check the following:

  1. Wiring:
  • Daisy-chain wiring topology is the only one allowed. Do not use free topology scheme
  • The polarity of the cable should be correct
Wattsense box Modbus device
A+ <–> A+
B- <–> B-
  1. Communication settings (i.e. Baudrate, parity, data bits, stop bits): They must be identical on each equipment.

  2. Slave id: it should be unique for each device on the network.

  3. With several equipment on the network, one of them can be wrongly configured, please try the following steps:

  • Isolate the bad device
    • Disconnect the modbus network at wattsense box level (unplug the green connector)
    • Connect the bad device directly to the box and try to communicate
  • Once it works, add it back to the network (following recommendation #1)

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