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Hi all,

I'm looking for help with an issue I've come across while trying to facilitate Modbus communication between a WAGO PFC200 PLC using a 750-652 communication module and an iEM2050 Series Single Phase Energy Meter.

I believe to have everything wired and setup correcty, but I keep running into a "Error time out" message, and by now I don't really know what else to try.

My setup is as follows: A PFC200 Wago PLC, which has 2 750-652 Serial Interfaces extension modules connected to its field bus. I'm using one of these to talk to a Schneider iEM2050 - kWh-meter over modbus.

I have connected terminal 23 (A) of the iEM2050 to connector 6 (A) on the 750-652. I have connected terminal 24 (B) of the iEM2050 to connector 2 (B) of the 750-652. I'm using 200mm of twisted together wires to connected them both, and I have placed a 120 ohm resistor between A and B at both ends. I've attached relevant pinout images to this post.

I then wrote a simple program that configures the Mobus port, as per the datasheet of the iEM2050. You can find an image of the relavent page attached to this post too.

This is my program:

PROGRAM PLC_PRG

VAR
    Master: FbMbMasterSerial;
    xIsConnected: BOOL;
    xError: BOOL;   
    iIndex: INT := 1;
    xTrigger: BOOL;

    utQuery : typMbQuery := (
                        bUnitId := 1,               // The Modbus unit or slave address
                        bFunctionCode := 4,         // Function code for reading input registers
                        uiReadAddress := 1829,        // adress for the Power on off counter 
                        uiReadQuantity := 1        // Quantity of registers to read 
                        );
    iStep: INT;
    oStatusModbus: WagoSysErrorBase.FbResult;
    utResponseModbus: typMbResponse;
    xConnect: BOOL := FALSE;
    delayTimer: TON;
END_VAR

Master(
    xConnect:= xConnect, 
    I_Port:= _750_652_24_1, 
    udiBaudrate:= 9600, 
    usiDataBits:= 8, 
    eParity:= WagoTypesCom.eTTYParity.Even, 
    eStopBits:= WagoTypesCom.eTTYStopBits.One, 
    eHandshake:= WagoTypesCom.eTTYHandshake.None, 
    ePhysical:= WagoTypesCom.eTTYPhysicalLayer.RS485_HalfDuplex, 
    xIsConnected=> xIsConnected, 
    xError=> xError, 
    oStatus=> oStatusModbus, 
    eFrameType:= WagoAppPlcModbus.eMbFrameType.RTU, 
    tTimeOut:= T#5S, 
    utQuery:= utQuery, 
    xTrigger:= xTrigger, 
    utResponse:= utResponseModbus);

delayTimer(IN := TRUE, PT := T#3S);

// Use the Q output of the timer to set xConnect after the delay
IF delayTimer.Q THEN
    xConnect := TRUE;
END_IF

CASE iStep OF
    0: //Wacht totdat de master de poort geopend heeft
        IF xIsConnected THEN
            iStep := 1;
        END_IF
    1: //Stuur request naar de slave
        xTrigger := TRUE;
        iStep := 2;
    2: //Wacht totdat de master klaar is met het afhandelen van de request
        IF NOT xTrigger THEN
            iStep := 3;
        END_IF
END_CASE

The TON delay before opening the port is due to a an error I encountered when opening it straight away. This seems to be a bug, as described here. However, the TON solved that particular issue.

I tried reading multiple registers, but like I said, I still always end up with the "Error time out".

What else can I test or try at this point?

750-652_pinout.png

Error_message.png

Meter_pinout.png

Settings_modbus_meter.png

registers_meter.png

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Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module

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Timeout Error in Modbus Communication with WAGO PFC200 and iEM2050 Meter using 750-652 Module