How to read Modbus RS485 on plc

CODESYS
42

hello,
Yes they are shorted together

43

Hello

I’m working on the same topic—I have n Socomec meters connected in “RS485” series, and I’m going to use the Wago 750-1652 card to read the various values.

I found this tutorial that might help us; on my end I still get a read error and I don’t know why, even though I followed the video closely.

Wago 750-8212 Modbus RTU Master \u0026 Third Party slave in Codesys 3.5

Feel free to get back to me if you’ve made any progress on the topic.

44

You can also do settings of the IO card with the WAGO IO-check software.

Maybe this can be checked also.

This is how I did it with a VEGA sensor:

image
image975×640 106 KB

Variables:

FbMbMasterSerial_Vega: WagoAppPlcModbus.FbMbMasterSerial := ( xConnect := TRUE,
udiBaudrate := 9600,
usiDataBits := 8,
eParity := WagoTypesCom.eTTYParity.None,
eStopBits := WagoTypesCom.eTTYStopBits.One,
eHandshake := WagoTypesCom.eTTYHandshake.None,
ePhysical := WagoTypesCom.eTTYPhysicalLayer.RS485_HalfDuplex,
eFrameType := eMbFrameType.RTU,
tTimeOut := T#200MS
);;

utQueryVEGA : typMbQuery := ( bUnitId := 246, // Slaveaddress
bFunctionCode := 16#04, // read input registers

uiReadAddress := 1300, // Startaddress
uiReadQuantity := 11, // Quantity of wanted registers
uiWriteAddress := 0, // not needed for FC4
uiWriteQuantity := 0, // not needed for FC4
awWriteData := [124(0)] // not needed for FC4
);

xTxTriggerVEGA      : BOOL;             (* Set this variable once for start a job.
                                       This variable will be automaticly reset by the master
                                       if the job is done.
                                    *)

utResponseVEGA      : typMbResponse;    (* After the job is done you can find at this structure
                                       the result.
                                    *)
45

Yes they are still connected as the picture, the total resistance is 60 ohm