Parallel Port

Hi,
get zlportio .. it's a delphi unit and a tiny 3kb sys file that lets you work easily with the ports..
it is sooo easy to use!
take a look at the control util here :

http://www.geocities.com/gacarpenter386/portie.zip

by the way to use the port to turn on/off a realy you must use ULN-2803A IC

try this link to download source and example :
http://www.specosoft.com/en/download.html

ULN-2803A IC is a valid way of doing things (AmirAzhdari)

Another way (which might eliminate the need for a relay, depending on your application) is to use an optoisolator

http://en.wikipedia.org/wiki/Optoisolator

Practically speaking, I mean:-

http://www.electronicsurplus.com/dictionary/cat2152.htm

Hi!

If you use a relay, put a didode inverse polarised, in parrallel with the coil, for avoid the inductive return, this is sufficient for make home things...

For example one diode 1N-4148 is sufficient for this porpouse.
In a proffesional circuit you must use any optical separation (optocoupler) for protect your pc.

ULN-2803 is a darlington transistor cell, used for attack a bigger relay (or a relay of other voltage), but... it doesnt a good isolator.... is just 'brute force' for your port :)

Here you have software examples for access ports in W2k/Xp:

http://www.q3.nu/trucomania/truco.cgi?556&ing

There is other solution: Solid States Relays. This components/packs/circuits contains all you need, has 'force brute', galvanic isolation, and fast & without noise conmutation but... are something expensives for make tests at home... :)

Does anyone knows how can I write byte to parallel by CreateFile, WriteFile & CloseHandle ?

Thanks,
Andrew

Dear andrewyu
i have see you asked that question before , just take a look at posted comment from Johnjces to know how to use createfile and...
http://www.torry.net/vcl/system/portaccess/smport.zip

http://www.experts-exchange.com/Programming/Programming_Languages/Delphi/Q_21375445.html

regards

Actually, how can I do it by Delphi 6 (rather than calling a external DLL) ?

Thanks,
Andrew

Let's say you wanna send a bunch of bytes:

var
  s: string;
  LPTHandle: THandle;
  bytesWritten: Integer;
begin
  LPTHandle := CreateFile('LPT1', GENERIC_WRITE, 0, PSecurityAttributes(nil),
    OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0);
  if LPTHandle = INVALID_HANDLE_VALUE then
    raise Exception.Create('Unable to open handle for LPT1!');
  s := 'Some string'; // or you can send a bunch of bytes such using s := #12#13#14;
  WriteFile(LPTHandle, PChar(s)^, Length(s), bytesWritten, nil);
end;

DragonSlayer,

How can I send a 0 or 1 (number) by WriteFile as I have to hold the status of the parallel port ?

Thanks,
Andrew

s := #1;
WriteFile(LPTHandle, PChar(s)^, Length(s), bytesWritten, nil);
- or -
WriteFile(LPTHandle, PChar(#0)^, 1, bytesWritten, nil);

Hi, DragonSlayer,

I still cannot work with following codes, what seems to be the problem ?

Thanks,
Andrew


  HandleFile:= CreateFile('LPT1',
                     GENERIC_WRITE,
                     0,
                     PSecurityAttributes(nil),
                     OPEN_EXISTING,
                     FILE_FLAG_OVERLAPPED,
                     0);
  if HandleFile= INVALID_HANDLE_VALUE then
  begin
    raise Exception.Create('Unable to open handle for LPT1!');
  end;

  WriteFile(HandleFile, PChar(#0)^, 1, NumberWritten, nil);
OR
  WriteFile(HandleFile, PChar(#1)^, 1, NumberWritten, nil);

  CloseHandle(HandleFile);