Mervis and Modpoll tool

Modpoll is a very nice testing tool but one needs to understand quite deeply the inner workings of Modbus protocol to use it properly.

Here are some basic examples that demonstrate how to poll Mervis RT Modbus Server.

.\modpoll.exe -a 1 -r 1 -c 4 -t 4:float -f  -1 -o 5 -p 502 192.168.1.120

• -a Modbus server address: 1
• -r register NUMBER 1 (PDU address = 0) - the same number you see in Modbus server definition in IDE
• -c read 4 elements
• -t interpret the values as floats
• -f - Mervis uses Big-Endian
• -1 poll the server just once
• -o timeout 5s
• -p read from the IP: 192.168.1.120 port 502