There are two devices:

  1. Eaton EM20/M (~like Northern Design Cube 400)
  2. Volison ADM-5850G

Connected them like:


Trying to get data from EM20/M which supports ModbusRTU(RS-485) protocol using ADM-5850G converter ModbusTCP<>ModbusRTU.

Converter(ADM-5850G) and Slave(EM20/M) are set for 9600 baud rate.
Also, the converter's settings:


Some EM20/M's programming pages:


Created a packet containing 00 01 00 00 00 06 01 03 9e 42 00 01 which should read 1 register at address 40515 from EM20/M which Slave ID is 1. Register's address got from references below(links).


Sent same packet using two tools(wireshark shows same result for both tools):

  1. modpoll(https://www.modbusdriver.com/modpoll.html)
    Command: modpoll -a 1 -r 40515 -c 1 -1 -l 1000 -o 0.5

  2. netcat
    Command: echo -en "\x00\x01\x00\x00\x00\x06\x01\x03\x9e\x42\x00\x01" | nc -w 1 502


  1. A "Cmd" on EM20/M led blinks one time after command having being sent and there's no response:

  2. 1 modpoll program outputs: Reply time-out!:


  1. 2 netcat just outputs nothing

The question:

Why is there no response?
Do we send a valid packet(also, note that "Cmd" led blinks shortly on EM20/M after command sent)?


  1. ModbusTCP: http://www.simplymodbus.ca/TCP.htm
  2. EM20/M manual we didn't find, but found Cube 400's: https://www.ndmeter.co.uk/brochures/Manuals/Cube%20400%20Manuals.zip
  • \$\begingroup\$ "like" Cube400 doesn't make it the same as EM20/M. aspects of the communications are likely different \$\endgroup\$ – JonRB Dec 31 '18 at 9:53
  • \$\begingroup\$ @JonBB, it's visually similar. There's no manuals for EM20/M at all. All aspects from manual of Cube400(programming, menu...) works well with EM20/M. \$\endgroup\$ – V.7 Dec 31 '18 at 9:59
  • \$\begingroup\$ Also, as you can see on programming page above(at EM20/M), it shows Cube Addr which means it's Cube's firmware. \$\endgroup\$ – V.7 Dec 31 '18 at 10:29

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