snowmakingcontrolppdev.c.txt

这是《嵌入式linux－硬件、软件与接口》一书对应的所有linux方面实例的源代码

/*
 * snowmakingcontrolppdev v0.1 9/25/01
 * www.embeddedlinuxinterfacing.com
 *
 * The original location of this code is
 * http://www.embeddedlinuxinterfacing.com/chapters/07/
 * snowmakingcontrolppdev.c
 *
 * Copyright (C) 2001 by Craig Hollabaugh
 *
 * This program is free software; you can redistribute it and/or modify 
 * it under the terms of the GNU Library General Public License as 
 * published by the Free Software Foundation; either version 2 of the 
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of 
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public 
 * License along with this program; if not, write to the 
 * Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

/* snowmakingcontrolppdev
 * snowmakingcontrolppdev uses /dev/parport0 to control an interface
 * circuit connected the PC parallel printer port. The port's 
 * control port drives the interface circuit's output latch signals.
 */

/*
 * For more information, see The Linux 2.4 Parallel Port Subsystem, T. Waugh
 * http://people.redhat.com/twaugh/parport/html/parportguide.html 
 */

/*
gcc -O2 -o snowmakingcontrolppdev snowmakingcontrolppdev.c
*/

#include <stdio.h>
#include <unistd.h>
#include <asm/io.h>
#include <linux/ioctl.h>
#include <linux/parport.h>
#include <linux/ppdev.h>
#include <fcntl.h>

#define SPPDATAPORT    0x378
#define SPPSTATUSPORT  (SPPDATAPORT + 1)
#define SPPCONTROLPORT (SPPDATAPORT + 2)
 
#define OUTPUTENABLE 0x02
#define OUTPUTLATCH  0x04

struct ppdev_frob_struct frob;

int main(int argc, char *argv[])
{
  int fd, mode;
  unsigned char status, data;

/* 1. get the file descriptor for the parallel port */
  fd = open("/dev/parport0",O_RDWR);
  if (fd == -1)
  {
    perror("open");
    exit(1);
  }

/* 2. request access to the port */
  if (ioctl(fd,PPCLAIM))
  {
    perror("PPCLAIM");
    close(fd);
    exit(1);
  }

/* 3. configure the port for SPP mode */
  mode = IEEE1284_MODE_COMPAT;
  if (ioctl(fd, PPNEGOT, &mode))
  {
    perror ("PPNEGOT");
    close (fd);
    return 1;
  }


/* 4. assert the latch's OUTPUTENABLE signal */
  frob.mask = OUTPUTENABLE ;
  frob.val = OUTPUTENABLE;
  ioctl(fd, PPFCONTROL, &frob);


/* 5. put the command line argument 1 on the data bus */
  ioctl(fd,PPWDATA,argv[1][0]);

/* 6. toggle the OUTPUTLATCH signal to latch data */
  frob.mask = OUTPUTENABLE | OUTPUTLATCH ;
  frob.val = OUTPUTENABLE | OUTPUTLATCH;
  ioctl(fd, PPFCONTROL, &frob);

  frob.mask = OUTPUTENABLE ;
  frob.val = OUTPUTENABLE;
  ioctl(fd, PPFCONTROL, &frob);

/* 7. release the port */
  ioctl (fd, PPRELEASE);

/* 8. close the device file */
  close(fd);
}