I set up the Do-more PLC Ethernet port as 192.168.1.34 and setup a wireless AP so I could communicate with it from my laptop wireless adaptor set at 192.168.1.30. I also used a MODBUS master simulator on the laptop to be sure I could read a holding register. It worked. I tried to read the same register using the sample Modbus-ONE. It tries to connect but comes up with an error. PLC Local IP:192.168.1.34:502 is what it shows for the connection. What should I use for the address to read 40001?
On some controllers address 40001 corresponds do Holding Register 1. So in ScadaMobile you must enter HR1. In any case, please can you disclose the error that you get?. Is it a connection error -on the connections tab- or a tag error -on the home tab next to the tag row- ?
When I removed
it started working and works great!
The error was “connection refused” but it must have been related to the reomte_host variable.
Thanks for the quick reply.
You should be able to use any Ethernet to serial adapter. Essentially you may find two kinds of converters:
(1) Modbus/TCP to Modbus/RTU converters
(2) simple Ethernet to Serial converter
The (1) perform an explicit conversion between modbus flavors. When using them you must set Modbus/TCP on the ScadaMobile app.
The (2) are cheaper as they simply remove the TCP header and push the rest through the serial line. They do not understand modbus. In this case you must set rtu_mode=1 on ScadaMobile. This tells the app to embed Modbus/RTU frames on TCP instead of producing actual Modbus/TCP frames. In this case the converter will simply output what is on the wire, which will be already Modbus/RTU on the serial side.
Both kind of converters will work, but (1) tends to be more reliable on the ethernet side because retries due to serial line failure or collisions will be handled by the converter firmware on the serial side.