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Port Access

, 17 Aug 2004
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A way to access parallel port in Windows XP

Introduction

At first I want to thank Mr. Tomas Franzon as I used his help a lot in this project. This code opens and closes 0x378 port ( printer port ) manually. In XP we have no permission to access external port like Printer. Here we copy a sys file to system32 and use it in the code so we can send and receive data through this port.

Using the code

For using the code you have to copy PortAccess.sys ( exists in source ) to system32\drivers. Then you can run the program.

For sending and receiving data we do this :

#include <conio.h>
#include <math.h>
// 

         // for sending data
         _outp(Port_Address,iByte); 

//

Return Value:

This function returns data output . There is no error return.

Parameters:

Unsigned short Port Number ( defined 0x378 )

Int Output value

         // for receiving data
         iByte=_inp(Port_Address); 

Return Value:

This function returns the byte, word or int from port. There is no error report

Parameters:

Unsigned short Port Number ( defined 0x378 )

When you check a check box the iBitOut value is Set or Reset.

// to set or reset a bit
iBitOut[i]=1-iBitOut[i];
 

When you click output button the Bits are changed to int value to send to port.

 
         // to send value to port

         iByte=0;

         for (i=0;i<=7;i++)

         {

                 iTemp=pow(2,i);

                 nIndex=iTemp*iBitOut[i];

                 iByte=iByte+nIndex;

         }

         _outp(Port_Address,iByte);
 

When you click input button the input value is read and iBitIn[i] becomes set or reset.

 

         // to get data from port 

         iByte=_inp(Port_Address);

         for (i=7;i>=0;i--)

         {

                 nIndex=pow(2,i);

                 if (iByte>=nIndex)

                 {        iByte=iByte-nIndex;

                          iBitIn[i]=1;

                 }

                 else iBitIn[i]=0;

         } 

For checking a check box we use code below :

         // to check a check box

         if (iBitIn[0]==1)
                 CheckDlgButton(hDlg,IDC_CHECKINPUT1,BST_CHECKED);
 

Points of Interest

I always work with peripheral devices. In these cases, communicating in parallel mode is more flexible and easier than the other modes like serial communication. So I am forced to go to this field. You can send and receive int, long, Byte, unsigned short, unsigned char etc as easy as possible.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

asef
Web Developer
Iran (Islamic Republic Of) Iran (Islamic Republic Of)
I live in Iran . I started hardware programming when I was young. I designed and built some ISA cards for attaching to PC.like ocsiloscope and signal generator. Now I am working for a engineering company and Manager of some project.

Comments and Discussions

 
GeneralMy vote of 4 PinmemberMember 870111428-Apr-12 22:19 
GeneralRun file PinmemberROVIO5-Oct-09 3:47 
Questionemergency help Pinmembermechatron19-Apr-08 0:39 
QuestionI have a problem with a parallel port, could you please help me? Pinmemberluixilva9-Oct-07 11:53 
QuestionInput Problem Pinmembermirispearl5-Sep-07 19:37 
Questiona question from lovers_ali PinadminSean Ewington6-Jun-07 8:41 
AnswerRe: a question from lovers_ali Pinmemberasef9-Jun-07 19:26 
GeneralPort access project PinmemberRupanagudi4-May-07 15:25 
GeneralRe: Port access project Pinmemberf227-May-07 16:49 
GeneralRe: Port access project Pinmemberasef9-Jun-07 19:42 
GeneralRe: Port access project PinmemberWamuti16-Nov-07 6:07 
Generalplotting a graph in VC++ PinmemberMember #343294419-Mar-07 22:07 
GeneralVisual C++ 6 Or Visual C++.Net 2005 Pinmembersaman_programing29-May-06 1:13 
GeneralRe: Visual C++ 6 Or Visual C++.Net 2005 Pinmemberasef29-May-06 2:40 
Questionejraye barname dar Turbo C++ 3.0 DOS Pinmembersaman_programing24-May-06 18:55 
AnswerRe: ejraye barname dar Turbo C++ 3.0 DOS Pinmemberasef26-May-06 18:49 
Generalserial ( COM) port accessing Pinmemberbala nagesh15-May-06 18:29 
GeneralRe: serial ( COM) port accessing Pinmemberasef15-May-06 20:14 
QuestionInput Probs Pinmemberbhaskar_gupta8-Feb-06 8:31 
I have set parallel port as EPP+ECP mode to ensure bidirectional data port. Yet when i am reading the port, it aways shows 255 as input no matter if its your above program or any other input program (as in i set t control bit CS 5 (37A) to 1 (value 32) to disable output).
Why if there is no external voltage lines, its not able to read it? i mean y its always reading 255 only?
 

 
Bhaskar Gupta

AnswerRe: Input Probs Pinmemberasef11-Feb-06 17:45 
GeneralHow to control parallel port by programming Visual C++ PinmemberBK200725-Dec-06 4:07 
GeneralParallel port Pinmemberdzldan2-Nov-05 10:46 
GeneralRe: Parallel port Pinmemberasef4-Nov-05 17:36 
GeneralRe: Parallel port PinmemberBK200725-Dec-06 4:05 
Generalport Programming Problem In XP PinmemberMasoud Aghapour7-Sep-05 17:49 

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