Parallel Port Pin Control Library (PaPiC)

• Download demo - 41 KB
• Download source - 25.1 KB

Introduction

This is a wrapper for the inpout32.dll/inpout32.lib class which is available at Logix4u.net. For a little theory, please visit Logix4u.net.

This class is useful if you wish to control the 12 output pins of your computer's parallel port under Windows XP/NT (e.g., driving LEDs, motors and all). This means, the control pins are used as output. The LPT port has 8 data pins, 4 control pins, and 5 status pins (input), but unfortunately, the basic functions (Console and Port I/O Routines) do not support direct access to the control pins. For this reason, I have developed this project: to have more freedom and functionality using the LPT port.

Almost all functions have the same interface as PARAPIN functions, so this class is useful too if you are adapting your linux code included PARAPIN to Windows enviroment. Hopefully you will find CPaPiC useful.

Background

This C++ class was inspired by PARAPIN, A Parallel Port Pin Programming Library for Linux, which was developed by Jeremy Elson and Al Hooton.

The realization of this work can never been done without the inpout32.dll/inpout32.lib from Logix4u.net.

Using the code

Important!

If you are using WinXP, do the following steps:

1. Execute regedit.exe:
2. Find the following registry key:

[HKEY_LOCAL_MACHINE\\\\SYSTEM\\\\CurrentControlSet\\\\Services\\\\Parport]

3. Insert a new key named "Parameters" (if it does not exist).
4. Insert a new double word named "DisableWarmPoll" into "Parameters" with value "1".
5. Restart Windows.

After this. WinXP will not disturb the output if you are switching the status pins.

Before using CPaPiC:

1. Copy the DLL file inpout32.dll and the lib file inpout32.lib to the project folder.
2. From the Project menu, select Settings, go to the tab Link, in Object/ Library Modules, write inpout32.lib.

You may use CPaPiC in different ways. For example, you can:

1. create a static or dynamic object, or
2. derive your class from CPaPiC.

At first, I will show you how to create a static object and use its member functions and definitions. In this case, it is possible to use more then one object and control only the selected pins without the danger of disturbing the others. Let me declare a CPaPiC object like this:

CPaPiC papi;

The constructor sets the default port LPT1, and selects all the input and output port pins that are active:

Physically:

Two additional definitions that refer to all I/O pins are LP_INPUT_PINS and LP_OUTPUT_PINS. The LPT port can be changed by the lpt_init_user() function. For example:

papi.lp_init_user(LPT2); // papi will control port LPT2

Furthermore, you may give different memory addresses. (But only LPT1 and LPT2 are defined.) If you want to select the pins to control, you can do it this way:

papi.pin_input_mode( LP_PIN10 | LP_PIN11 | LP_PIN12 );
// Set input pins 10, 11 and 12 active

papi.pin_output_mode( LP_PIN01 | LP_PIN02 );
// Set output pins 1 and 2 active

// Equivalent code:

papi.pin_mode( LP_PIN10 | LP_PIN11 | LP_PIN12, LP_INPUT );
papi.pin_mode( LP_PIN01 | LP_PIN02, LP_OUTPUT );

Now, only the 10, 11, 12 input pins and the 1, 2 output pins will be available for the papi object. The port address and active pins are revisable any time. Controlling the selected pins is very simple. Just have a look at these (PARAPIN-like) functions:

For example:

papi.clear_pin(LP_OUTPUT_PINS);
// Set all pins low (if not all have
// been selected, set only selected)

papi.set_pin( LP_PIN01 ); // Set pin 1 high

papi.invert_pin( LP_PIN01 | LP_PIN02 ); // Invert pins 1 and 2


// Loading the values of input pin registers:

lp_pin pins; // Creat a new lp_pin varible

pins = papi.pin_is_set( LP_PIN10 | LP_PIN11 | LP_PIN12 );
// ask the state of the registers of pins 10, 11 and 12

for( int i = 10; i < 13; i++)
    if( pins & LP_PIN[i] == 0 )
        printf( "pin %d is low\n", i );
        // the pin number i is low

    else
        printf( "pin %d is high\n", i ); // the pin number i is high

In the demo program, you can specify the pin parameters of a function using check boxes (parameter of pin_is_set(..) contains all input pins):

I have derived the CPaPiCDlg class from CPaPiC, so my dialog has all the properties of CPaPiC. So, I can use all its functions instead of creating a separate CPaPiC object.

Points of interest

While writing the code, I learned how important the bit operations are.