Lpt Port And Python Using SWIG to build python wrappers

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Some time ago i was asked to program device, connected to PC parallel port. Main program was written in python.

First of all i found nice C library which perform the task: parapin. Building and installation is straightforward, so i don't stop on this.

Then i start to build python wrapper. With SWIG its easy.

First create file parapin.i, here is head of it:

%module parapin

%{

#include <parapin.h>

%}

 

int pin_init_user(int lp_base);

#define LPT1 0x378

#define LPT2 0x278

 

void set_pin(int pins);

void clear_pin(int pins);

void change_pin(int pins, int state);

#define LP_CLEAR 0 /* for change_pin */

#define LP_SET 1 /* for change_pin */

Actually i wrote only first 3 line, rest is copypasted from library header paragui.h. I take only those functions and definitions, which i need for my task.

 

Then i wrote make config file Makefile:

all: _parapin.so

 

_parapin.so: parapin_wrap.o

gcc -o _parapin.so -shared parapin_wrap.o -lparapin

 

parapin_wrap.o: parapin_wrap.c

gcc -fpic -c parapin_wrap.c -I/usr/include/python2.4/ -I/usr/local/include

 

parapin_wrap.c: parapin.i

swig -python parapin.i

 

 

After running make utility i had ready for use python module parapin.py with functions set_pin, clear_pin and so on.

 

Not so hard, isnt't it?