I believe this topic has been write so many times in internet and you can find so many articles about it, but i want to share my experience programming pararel port with delphi. I started to do this project when i was doing some vision system project in printing company. When i got this project i started to learn about programming pararel port with delphi. One good source that i´ve found is http://et.nmsu.edu/~etti/fall96/computer/printer/printer.html This is very good source. ( but it use C language ).
The easiest port to control and access in the computer is pararel port ( LPT1, LPT2, LPT3 ). You can use this port to control your home appliance, electricity , robotic and also you can use it to make data acquisition. This port come in with female DB25 connector ( ussualy ) pic like image below :
| Pin # | Pin Name | Pin Description and Function |
|---|---|---|
| 1 | /STROBE | Strobe |
| 2 | D0 | Data Bit 0 |
| 3 | D1 | Data Bit 1 |
| 4 | D2 | Data Bit 2 |
| 5 | D3 | Data Bit 3 |
| 6 | D4 | Data Bit 4 |
| 7 | D5 | Data Bit 5 |
| 8 | D6 | Data Bit 6 |
| 9 | D7 | Data Bit 7 |
| 10 | /ACK | Acknowledge |
| 11 | BUSY | Busy |
| 12 | PE | Paper End |
| 13 | SEL | Select |
| 14 | /AUTOFD | Autofeed |
| 15 | /ERROR | Error |
| 16 | /INIT | Initialize |
| 17 | /SELIN | Select In |
| 18 | GND | Strobe Ground |
| 19 | GND | Data bit 1 and 2 Ground |
| 20 | GND | Data bit 3 and 4 Ground |
| 21 | GND | Data bit 5 and 6 Ground |
| 22 | GND | Data bit 7 and 8 Ground |
| 23 | GND | Busy and Fault Ground |
| 24 | GND | Paper out, Select, and Acknowledge Ground |
| 25 | GND | AutoFeed, Select input and Initialize Ground |
Today computer ussualy come with 1 pararel port and 1 address, but last time it can came with 3 pararel port and 3 address.The address of pararel port listed like below :
Printer Data Port Status Control
LPT1 0x03bc 0x03bd 0x03be LPT2 0x0378 0x0379 0x037a LPT3 0x0278 0x0279 0x027aMy experience pararel port address is using $378 for data port and $379 for status and $37A for control port.in order to make my program easier i use io.dll. an io.dll is small dll program that you can download it from internet. it is free and easy to use ( even i use it on win-xp operating system ). This program is small procedure / function to connecting your delphi program and your pararel port. Please put this io.dll in one folder with your application program.
The electronic things
we can use simple electronic circuit like schematic below to test our program. if you dont have electronic experience you can ask your friend who know about electronic circuit to assembly this schematic.
Programming
Write simple program in delphi like code below :
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
Edit1: TEdit;
Label1: TLabel;
Button1: TButton;
Button2: TButton;
Edit2: TEdit;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
input1:integer;
implementation
function PortIn(Port:Word):Byte;stdcall;external'io.dll';
procedure PortOut(Port:Word;Data:Byte); stdcall; external'io.dll';
{$R *.dfm}
// this procedure to light on LED on port 378
procedure TForm1.Button1Click(Sender: TObject);
begin
PortOut($378,$01); //this will light on 1 LED on pin number 2, you can change this value
end;
//this procedure is to read any value from port 379
procedure TForm1.Button2Click(Sender: TObject);
begin
input1:= PortIn($379) xor $80;
Edit1.Text:= IntToStr(input1);
end;
end.
you can make some experiment with this circuit and programming with any programming language, in this story i use delphi.
