Hi,

I try to connect a Raspberry PI3 as Modbus TCP master with an arduino slave (ESP8266).

But I'm facing some trouble.

Slave side seems to be correctly configured because it is working fine with Modbus Doctor (Windows Software simulating Modbus Master).

Can someone tell me what's going wrong with my setup?

You will find WireShark captures, codesys project and printscreens.

Thanks for your help.

EDIT :

OK I find that I need to read the variable in a POU to make the modbus values refreshing.

But when I look at the Wireshark capture, the transaction ID is increasing each time the master requests a register.

Why is this happen with codesys and not happen with Modbus Doctor?

CodesysRaspberryModbusTCPMaster1.zip [390.19 KiB]