Delphi – exchange data with Siemens PLC

Other interesting possibilities for using LibNoDave library is NoDave component for Delphi API. The Unit NoDaveComponent implements the class TNoDave, which encapsulates the access to the libnodave.dll. With TNoDave and libnodave.dll it is very easy to read and write data from and to a S7 PLC. TNoDave uses a worker-thread for asynchronous connecting with the PLC.

This source files which are necessary to connect PLC:

• nodave.pas – that unit includes variables, conventions (where are name of function, name of file, where function is located and information on how it to use) and functions itself.
• nodavecomponent.pas – NoDave component.
• libnodave.dll – that is communication library itself.

Add nodave.pas file in the Delphi project and copy libnodave.dll file in the same directory. But nodavecomponent need to register. How to install a third-party Delphi component you can read in the site: Installing a single source Delphi component into an existing Package.

Structure of the application:

Source of the example of the Delphi application available for download.

After the first glance is useful. Separate a worker-thread for asynchronous connecting with the PLC. Make a list of the required data, enabling the driver and you have a date. But if necessary to read data from different locations and of different types, then may be useful to use the DLL directly.

Example of using LibNoDave library directly.

This source files which are necessary to connect PLC:

• nodave.pas
• libnodave.dll

Usage of the functions connect, disconnect, read and write data:

– Connection

procedure TMainForm.Connect;
<pre>Var
  ComName:Array[0..20] of Char;
  Fds:_daveOSserialType;
  S:String;
  i:Integer;
begin
  S:=Trim(IPAddress);
  For i:=1 To Length(S) Do
    ComName[i-1]:=S[i];
  ComName[Length(S)]:=#0;
  fds.rfd:=openSocket(102,COMname);
  fds.wfd:=fds.rfd;

  verbinding := false;
  if (fds.rfd>0) then
  begin
    dcIn:=daveNewInterface(fds, 'IF1',0,ConnProtocol, MPISpeed);
    dcIn^.timeout:=IntfTimeout;
    if (daveInitAdapter(dcIn)=0) then
    begin
      dc :=daveNewConnection(dcIn,2, CPURack, CPUSlot);
      if (daveConnectPLC(dc)=0) then
      begin
        verbinding := true;
      end;
    end;
  end;
end;

procedure TMainForm.Disconnect;
begin
  if connected then
  begin
    daveDisconnectPLC(dc);
    daveDisconnectAdapter(dcIn);
    connected := false;
  end;
end;

– Write data to PLC

//Write S7 FLOAT
procedure TMainForm.WriteDouble(varR:single);
var
 Res:LongInt;
 VarD : longint;
begin
 VarD := daveToPLCfloat(varR);
 res := daveWriteBytes(dc, daveDB, ValueAdresDb, ValueAdresNum, 4, @varD);
end;

//write DINT, DWORD, INT, WORD
procedure TMainForm.WriteInt(varI : integer, type : boolean);
var
 varW : integer;
 varC, varD : word;
 Res:LongInt;
begin
 if  type = true then
 begin
   varW := daveSwapIed_32(varI);
   res := daveWriteBytes(dc, daveDB, ValueAdresDb, ValueAdresNum, 4, @varW)
 end else begin
   varC := varI;
   varD := daveSwapIed_16(varC);
   res := daveWriteBytes(dc, daveDB, ValueAdresDb, ValueAdresNum, 2, @varD)
 end;
end;

– Read data from PLC


procedure TMainForm.ReadData;
var
  Res:LongInt;
  i : integer;
  value1 : Array[0..3] of double;
Begin
  if verbinding then
  begin

    //Read 3x float values begin address DB110.DBD12
    res := daveReadBytes(dc, daveDB, 110, 0, 12, NIL);
    For i := 0 to 2 do
      value[i] := daveGetFloat(dc);
    Label1.Caption := Format('%f', [value1[0]]  );
    Label2.Caption := Format('%f', [value1[1]]  );
    Label3.Caption := Format('%f', [value1[2]]  );

    //Read BYTE
    res := daveReadBytes(dc, daveFlags, 0, 24, 1, NIL);
    Label4.Caption := IntToStr(daveGetU8(dc));

    //Read WORD
    res := daveReadBytes(dc, daveFlags, 0, 16, 2, NIL);
    Label5.Caption := IntToStr(daveGetU16(dc));

    //Read DWORD
    res := daveReadBytes(dc, daveFlags, 0, 2, 4, NIL);
    Label6.Caption := IntToStr(daveGetU32(dc));
 end
end;

During development of PLC control software often requires testing operation of the PLC software. Therefore necessary to simulate operation of the equipment controlled by PLC.
The purpose of the example, simulate and visualize the operation of devices connected to the PLC. Source of the example:

The structure of Delphi example is very simple. First application reads communication settings, then connect to PLC via ISO on TCP protocol. If connection is successful, then timer periodically reads outputs data from PLC and update user interface of the application, makes manipulations with bits and writes inputs data to PLC.

Reading from PLC outputs, simulation, manipulation with bits and writing inputs to PLC.

Step 1. Reading digital outputs: With function DaveReadBytes(dc, daveOutputs, 0, 0, 4, nil) read data from outputs memory area of the PLC  in the buffer as a sequence of bytes and with function “daveGetU8(dc)” read out of the buffer, the data with the byte format.

Step 2, 3 and 4: Manipulation with bits. For manipulation of bits use MatBit8.pas unit. With functions “SetBit(i)” or “ClrBit(i)” write “1″ or “0″ in the appropriate bit in the byte of the “inputDG” array of bytes depending on the bit in the byte of output array.

Step 5. Writing digital inputs: With function DaveWriteBytes(dc, daveOutputs, 0, 0, 4, @inputsDG) write sequence of bytes (4) to PLC.

Simulation analog values and writing to PLC analog inputs.

varW : integer;

varW := daveSwapIed_32(value);
res := daveWriteBytes(dc, daveInputs, 0, Address, 4, @varW);

Example of the full simulations of Waste Water Purification Installation of the oil company in Rotterdam. Simulation van motors, pumps, valves, process, level of the tanks, engine electric current and speed, flow control. Connection with two Siemens 317 PLCs.

Example of the full simulations of RSP Uniwax rotary printing machine of Vlisco company in Netherlands. Simulation of the HMI and inputs. Visualization of the outputs and control processes.