Programming PC parallel port with delphi 6.0

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Parallel Port Programming with Delphi

This article demonstration how to access parallel port with delphi 6. to access parallel port for all Windows platform i use driver file inpout32.dll becuase it easily to use with delphi.You can dowload from http://www.logix4u.net and it included in the example which you can download at the buttom of this page.

PC Parallel Port Basic

As we know the standard parallel port have 3 port for controll
1. Status port
2. Control Port
3. Data Port

each port have own address like this

Register	LPT1	LPT2
data registar(baseaddress + 0)	0x378	0x278
status register (baseaddress + 1)	0x379	0x279
control register (baseaddress + 2)	0x37a	0x27a

Pin No (DB25)	Signal name	Direction	Register - bit	Inverted
1	nStrobe	Out	Control-0	Yes
2	Data0	In/Out	Data-0	No
3	Data1	In/Out	Data-1	No
4	Data2	In/Out	Data-2	No
5	Data3	In/Out	Data-3	No
6	Data4	In/Out	Data-4	No
7	Data5	In/Out	Data-5	No
8	Data6	In/Out	Data-6	No
9	Data7	In/Out	Data-7	No
10	nAck	In	Status-6	No
11	Busy	In	Status-7	Yes
12	Paper-Out	In	Status-5	No
13	Select	In	Status-4	No
14	Linefeed	Out	Control-1	Yes
15	nError	In	Status-3	No
16	nInitialize	Out	Control-2	No
17	nSelect-Printer	Out	Control-3	Yes
18-25	Ground	-	-	-

* leading n = Active low or invert logic

How to use inpout32.dll with Delphi

After download inpout32.dll copy it to Windows\system32\

1. Open Delphi program
2. place component on from like this

3. write program following

1: unit main;
2: interface
3: uses
4:   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
5:   Dialogs, StdCtrls;
6: type
7: TForm1 = class(TForm)
8:     Button1: TButton;
9:     Button2: TButton;
10:   Edit1: TEdit;
11:   Label1: TLabel;
12:   Label2: TLabel;
13:   procedure Button1Click(Sender: TObject);
14:   procedure Button2Click(Sender: TObject);
15:  private
16:  { Private declarations }
17:  public
18:  { Public declarations }
19:  end;
20:
21: var
22: Form1: TForm1;
23: 
24: procedure Out32(wAddr:word;bOut:byte); stdcall; external 'inpout32.dll'
25: function Inp32(wAddr:word):integer; stdcall; external 'inpout32.dll'
26:
27: implementation
28:
29: {$R *.dfm}
30:
31: procedure TForm1.Button1Click(Sender: TObject);
32: begin
33:           Out32($378,$53);   // Out32
34: end;
35:
36: procedure TForm1.Button2Click(Sender: TObject);
37: begin
38:       edit1.Text:=IntToHex(Inp32($378),2);  //  Edit1
39: end;
40: end.

This program load inpout32.dll in static type in line 24,25.In event Button1Click program send data(53h) to data port (378h) in line 33. In line 38 we can read data(8 bit ) from data port(Set to bidirection Port only)

This picture used to test for output

Download example