#308 - How to troubleshoot a Modbus TCP communication

- From Windows PowerShell confirm the port of the connection:

TCP test connection on the target port, e.g.,

Test-NetConnection 192.168.0.1 -port 502

- From nmap: Check open ports, e.g.,

nmap -e eth3 192.168.0.1 -p 502

Note that the flag -e forces nmap to use a specific NIC. The NICs can be displayed using the command nmap --iflist

#303 - Modbus RS485 tips

- Wiring:

Sensor 24V supply, Sensor 0V Ground, RS485 (+), RS485 (-).

PLC Modbus Comms card: connect the M input pin to the Ground, A to RS485 (-) and B to RS485 (+).