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Setting up CODESYS Modbus TCP (SP16 or higher)


This tutorial shows how to connect CODESYS to Factory I/O through Modbus TCP. By following these instructions, you will create a new CODESYS project, configure it to work with Factory I/O and program CODESYS Control Win (SoftPlc) to control the Sorting by Height (Advanced) scene.

The sample code used in this tutorial is based on the solutions found in the book Industrial Automation Practices.

Creating the Project

  1. Start CODESYS and create a new project.

  2. Select Standard project from the Templates list and choose a name for the project (e.g. Tutorial). Click on OK.

    create new codesys project

  3. On the Standard Project window select the Device CODESYS Control Win V3 (3S - Smart Software Solutions GmbH) and Structured Text (ST) for the PLC_PRG. Click on OK.

    select project device

  4. Right-click on Application and select Add Object > Global variable List.... Type FIO as the list name, click on Add.

    add global variable list

  5. Open the FIO list by Double Left-clicking on it and copy and paste the following global variables. These variables will be used to exchange data between Factory I/O and CODESYS through Modbus TCP (these are the I/O points).

        iAtEntry        : BOOL;
        iLowBox         : BOOL;
        iHighBox        : BOOL;
        iAtTurnEntry    : BOOL;
        iAtLoadPos      : BOOL;
        iAtUnloadPos    : BOOL;
        iAtFront        : BOOL;
        iAtRightEntry   : BOOL;
        iAtLeftEntry    : BOOL;
        iAtRightExit    : BOOL;
        iAtLeftExit     : BOOL;
        oFeederConveyor : BOOL;
        oEntryConveyor  : BOOL;
        oLoad           : BOOL;
        oUnload         : BOOL;
        oTurn           : BOOL;
        oLeftConveyor   : BOOL;
        oRightConveyor  : BOOL;

    global variable list

  6. In the Device tree Double Left-click on PLC_PRG (PRG) and copy and paste the following variables. These are the variables you will be using in your program.

        F_AtEntry           : F_TRIG;
        F_AtTurnEntry       : F_TRIG;
        F_AtRightEntry      : F_TRIG;
        F_AtLeftEntry       : F_TRIG;
        F_AtRightExit       : F_TRIG;
        F_AtLeftExit        : F_TRIG;
        Pallet_on_left      : BOOL := FALSE;
        Pallet_on_right     : BOOL := FALSE;
        Idle                : BOOL := TRUE;
        Charging            : BOOL := FALSE;
        Turns_charged       : BOOL := FALSE;
        Discharging         : BOOL := FALSE;
        Turns_Discharged    : BOOL := FALSE;
        Turntable_busy      : BOOL := FALSE;
        Discharge_direction : BOOL := FALSE;
        Entry_busy          : BOOL := FALSE;
        Pallet_on_entry     : BOOL := FALSE;
        Count               : WORD := 16#8000;

    program variables

  7. Now, copy and paste the following code. This is the program that will control the Sorting by Height (Advanced) scene.

    F_AtEntry(CLK := FIO.iAtEntry);
    F_AtTurnEntry(CLK := FIO.iAtTurnEntry);
    F_AtRightEntry(CLK := FIO.iAtRightEntry);
    F_AtLeftEntry(CLK := FIO.iAtLeftEntry);     (* A pallet abandons the turntable, being charged onto the left exit conveyer *)
    F_AtRightExit(CLK := FIO.iAtRightExit);
    F_AtLeftExit(CLK := FIO.iAtLeftExit);       (* A pallet abandons the left exit conveyer *)
    (* Pallet_on_left represents the state of the left exit conveyer: if it carries a pallet, then Pallet_on_left = TRUE *)
    IF F_AtLeftExit.Q THEN                      (* When a pallet abandons the conveyer *)
        Pallet_on_left := FALSE;                (* Reset Pallet_on_left *)
    IF FIO.iAtLeftEntry THEN                    (* When there’s a pallet at the entry of the conveyer *)
        Pallet_on_left := TRUE;                 (* Set Pallet_on_left *)
    FIO.oLeftConveyor := Pallet_on_left;        (* Left exit conveyer runs for Pallet_on_left = TRUE *)
    IF F_AtRightExit.Q THEN
        Pallet_on_right := FALSE;
    IF FIO.iAtRightEntry THEN
        Pallet_on_right := TRUE;
    FIO.oRightConveyor := Pallet_on_right;
    (**** TURNTABLE CONTROL ****)
    IF Idle AND FIO.iAtTurnEntry THEN
        Idle := FALSE;
        Charging := TRUE;
    IF Charging AND FIO.iAtFront THEN
        Charging := FALSE;
        Turns_charged := TRUE;
    IF Turns_charged AND FIO.iAtUnloadPos THEN
        Turns_charged := FALSE;
        Discharging := TRUE;
    (* The turntable discharges now onto both conveyers. Thus: *)
    IF Discharging AND (F_AtRightEntry.Q OR F_AtLeftEntry.Q) THEN
        Discharging := FALSE;
        Turns_Discharged := TRUE;
    IF Turns_Discharged AND FIO.iAtLoadPos THEN
        Turns_Discharged := FALSE;
        Idle := TRUE;
    IF F_AtTurnEntry.Q THEN
        Turntable_busy := TRUE;
    IF Idle THEN
        Turntable_busy := FALSE;
    (* Computing control outputs according to the current state of the turntable and the direction of the discharge *)
    FIO.oLoad := Charging OR Discharging AND Discharge_direction;
    (* oUnload is TRUE if the discharge is onto the left conveyer *)
    FIO.oUnload := Discharging AND NOT Discharge_direction;
    (* oTurn is TRUE if the discharge is onto the right conveyer *)
    FIO.oTurn := Turns_charged OR Discharging;
    IF F_AtEntry.Q THEN
        Count := ROL (Count,1);
        IF (Count = WORD#16#2) THEN
            Entry_busy := TRUE;
    IF F_AtTurnEntry.Q THEN
        (** Defining the direction of the discharge: the direction of the discharge changes every time a pallet is
        discharged from the entry conveyer onto the turntable. If Discharge_direction = FALSE, then the discharge is onto the right conveyer **)
        Discharge_direction := NOT Discharge_direction;
        Entry_busy := FALSE;
        Count := ROR(Count,1);
        IF (Count = WORD#16#8000) THEN
            Pallet_on_entry := FALSE;
    IF FIO.iAtEntry THEN
        Pallet_on_entry := TRUE;
    FIO.oEntryConveyor := Pallet_on_entry AND (NOT Turntable_busy OR NOT FIO.iAtTurnEntry);
    FIO.oFeederConveyor := NOT Entry_busy OR NOT FIO.iAtEntry;


  8. Right-click on CODESYS Control Win PLC icon (Systray) and select Start PLC.

    codesys softplc

  9. Get back to CODESYS and in the project tree, Double Left-click on Device (CODESYS Control Win V3) and then on Communication Settings. Now, click on Scan network... and select the network path to the controller. Click on OK.

    select device

  10. In the toolbar click on Build > Build (F11).

  11. Now, Right-click on Application and select Add Object > Symbol Configuration. Next click on Add. Now, check the FIO symbols and click on Build.

    fio symbols

  12. Right-click on Device (CODESYS Control Win V3) (1) and select Add Device.... Next, expand Fieldbusses > Ethernet Adapter and click on Ethernet (2). Click on Add Device.

    codesys add ethernet

  13. Right-click on Ethernet (1) and select Add Device..., expand Fieldbusses > Modbus > Modbus TCP Slave Device and select Modbus TCP Slave Device (2). Next, click on Add Device.

    codesys add modbus

  14. Double-click on Modbus TCP Slave Device (added in the previous step) and open General. Tick the Discrete Bit Areas box and enter the number of Coils and Discrete Inputs as shown below.

    codesys modbus general

  15. Now, open Modbus TCP Slave Device I/O Mapping (1) and map the global variables (2) defined in step 5 as shown in the image below.

    tag mapping

  16. Next, click on Online > Login (Alt+F8). When prompted to download the program to the PLC, click on Yes.

  17. Finally, click on Debug > Start (F5).

Setting up Factory I/O

  1. Open a scene in Factory I/O and click on File > Drivers. Choose Modbus TCP/IP Client from the drop-down list. Next, click on Configuration.

    fio drivers

  2. Set the Slave ID to either 0 or 255. Next, set the I/O Points as shown in the image below.


    When working with SP16, the Slave ID has to be set to either 0 or 255. The Modbus TCP specification followed by CODESYS 3.5 SP16 states that the Modbus server is addressed using its IP address, and therefore the Modbus Unit Identifier is useless.

    fio driver configuration

  3. Go back to the Driver menu and click on CONNECT. A successful connection is indicated by a green icon next to the selected driver, as well as next to the driver's name displayed on the status bar.

    fio connected

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