颜强的ds18b20驱动

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

/*和引脚相关的宏定义*/

#define DQ S3C2410_GPH9

#define CFG_IN S3C2410_GPH9_INP

#define CFG_OUT S3C2410_GPH9_OUTP

static int opencount = 0;

unsigned char init_ds(void)//ds18b20复位，返回0成功，返回1失败

{

  unsigned char ret = 0;

  s3c2410_gpio_cfgpin(DQ, CFG_OUT);

  s3c2410_gpio_pullup(DQ, 0);

  s3c2410_gpio_setpin(DQ, 1);

  s3c2410_gpio_setpin(DQ, 0);

  udelay(500);

  s3c2410_gpio_setpin(DQ, 1);

  udelay(50);

  s3c2410_gpio_cfgpin(DQ, CFG_IN);

  udelay(200);

  ret = s3c2410_gpio_getpin(DQ);

  s3c2410_gpio_cfgpin(DQ, CFG_OUT);

  s3c2410_gpio_pullup(DQ, 0);

  s3c2410_gpio_setpin(DQ, 1);

  return ret;

}

void write_byte(char data)//向18b20写一个字节

{

  char i = 0;

  s3c2410_gpio_cfgpin(DQ, CFG_OUT);

  s3c2410_gpio_pullup(DQ, 1);

  for(i=0; i<8; i++){

    s3c2410_gpio_setpin(DQ, 0);

    udelay(10);

    s3c2410_gpio_setpin(DQ, 1);

    s3c2410_gpio_setpin(DQ, data&0x01);

    udelay(60);

    s3c2410_gpio_setpin(DQ, 1);

    udelay(2);

    data >>= 1;

  }

}

unsigned char read_byte(void)//从18b20读一个字节

{

  unsigned char i;

  unsigned char data=0;

  s3c2410_gpio_cfgpin(DQ, CFG_OUT);

  s3c2410_gpio_pullup(DQ, 0);

  for(i=0; i<8; i++)

    {

      s3c2410_gpio_setpin(DQ, 0);

      udelay(1);

      s3c2410_gpio_setpin(DQ, 1);

      s3c2410_gpio_cfgpin(DQ, CFG_IN);

      udelay(10);

     

      data >>= 1;

      if(s3c2410_gpio_getpin(DQ))

    data |= 0x80;

      udelay(50);

      s3c2410_gpio_cfgpin(DQ, CFG_OUT);

      s3c2410_gpio_pullup(DQ, 0);

      s3c2410_gpio_setpin(DQ, 1);

      udelay(2);

    }

  return data;

}

/*文件的写函数，没有实际意义，用户不能写文件*/   

static ssize_t ds18b20_write(struct file *filp, const char *buffer,

             size_t count, loff_t *ppos)

{

  return 10;//随便返回一个正整数

}

/*18b20的读函数，读出的温度只保留了整数*/

static ssize_t ds18b20_read(struct file *filp, char *buffer,

             size_t count, loff_t *ppos)

{

  unsigned char a=0, b=0;

  unsigned int t=0;

  unsigned char temp=0;

  unsigned char flag;

  flag = init_ds();

  if(flag&0x01)

    return -1;

  write_byte(0x0cc);

  write_byte(0x44);

  udelay(500);

  flag = init_ds();

  if(flag&0x01)

    return -1;

  write_byte(0x0cc);

  write_byte(0x0be);

  a = read_byte();

  b = read_byte();

 

  flag = init_ds();

  temp = ((b & 0x7) << 4)) | (a >> 4);

  copy_to_user(buffer, &temp, 1);

  return 1;

}

static int ds18b20_open(struct inode *node, struct file *file)

{

  unsigned char flag;

  if(opencount == 1)

    return -EBUSY;

  flag = init_ds();

  if(flag&0x01)

    {

      printk("uable to open device!\n");

      return -1;

    }

  else

   {

      opencount++;

      printk("device opened!\n");

      return 0;

   }

}

static int ds18b20_release(struct inode *node, struct file *file)

{

  opencount--;

  printk("device released!\n");

  return 0;

}

static struct file_operations ds18b20_fops = {

  .owner = THIS_MODULE,

  .write = ds18b20_write,

  .read = ds18b20_read,

  .release = ds18b20_release,

  .open = ds18b20_open,

};

static int ds18b20_probe(struct platform_device *pdev)

{

  int ret;

  s3c2410_gpio_cfgpin(DQ, CFG_OUT);

  s3c2410_gpio_setpin(DQ, 0);

  ret = register_chrdev(0, "ds18b20", &ds18b20_fops);

  if(!ret)

    printk("--------------Uable to register driver!-------------------\n");

  printk("Probe for ds18b20 finished!\n");

  return 0;

}

static struct platform_driver ds18b20 =

{

  .probe = ds18b20_probe,

  .driver = {

    .name = "s3c2410-ds",

    .owner = THIS_MODULE,

  },

};

int __init ds18b20_init(void)

{

  printk("Initial driver for ds18b20......................\n");

  return platform_driver_register(&ds18b20);

}

void __exit ds18b20_exit(void)

{

  return platform_driver_unregister(&ds18b20);

}

module_init(ds18b20_init);

module_exit(ds18b20_exit);

MODULE_AUTHOR("[e-mail]");

MODULE_DESCRIPTION("DS18B20 driver for s3c2410");

MODULE_LICENSE("GPL");