Hello,
is there any modbus/TCP example with two Rasperry Pi ?

Thank you in advance
Best Regards
Leonhard Stiegler

Hello,
I'm lookig for same connection, do you have some new info about connesc 2 RPis via Modbus?

Thank you.

Master Modbus

1) Add device : Ethernet > Ethernet adapter
2) Set ethernet adapter: Double click on it, set interface, IP ...
3) Add device : Modbus > Modbus TCP Master
4) Set Modbus Master device : Mark auto-reconnect
5) Add device : Modbus > Modbus TCP Slave
6) Set Modbus Slave device :
General: Set Slave (2nd RPi) IP address, port, unit ID
Slave Channel: Add channel (Reading -FC4 / Writing -FC16 / Both -FC23), set offset to 0x0000, set length
Add I/O mapping, I'm using full address to WORD, like "Application.PLC_PRG.modbusIn", where "modbusIn" are devined at PLC_PRG as "modbusIn : ARRAY [0..3] OF WORD;"
7) Go to Device (CODESYS ... Raspberry Pi) > PLC settings and set Bus cycle task to "MainTask"
Compile
9) If you are getting some warnings declared variables at library, make a change at LibraryManager. Set version of IoDrvModbusTCP from "3.5.6.0" to "3.5.4.0".
10) Compile
11) It's done

Modbus Slave
1) Add device : Ethernet > Ethernet adapter
2) Set ethernet adapter: Double click on it, set interface, IP ...
3) Add device : Modbus > Modbus TCP Slave
4) Set Modbus Slave device :
General: Set slave port, ID, WORD length
Add I/O mapping, I'm using full address to WORD, like "Application.PLC_PRG.modbusOut", where "modbusOut" are defined at PLC_PRG as "modbusOut" : ARRAY [0..3] OF WORD;"
Set bus cycle and updating variables to "Use parent device/bus setting"
5) Go to Device (CODESYS ... Raspberry Pi) > PLC settings and set Bus cycle task to "MainTask"
6) Compile
7) It's done

Both Upload
Run Both device program
All done and data are flowing, I hope

Hallo,

ich need some help to get run my two pis over modbus/tcp.
I have done all steps (Master Modbus) in the description of "jvondrus", but my modbus slave dont run?
What "set length" I need?

What can I do?

Hi,

use attched example.
BR
Edwin

2RaspisModbusMasterSlaveCommunication.project [86 KiB]

Edwin Schwellinger hat geschrieben:
Hi,
use attched example.
BR
Edwin

Thank you, very much!
Now I've understand it...and the two rapsberry runs!