S3C6410 DS18B20温度传感器驱动（二） --- 时序分析

1.初始化序列

 

unsigned int init_ds18b20(void)
{
 unsigned tmp;
 unsigned int val;

 s3c_gpio_cfgpin(ds18b20_table[0],S3C_GPIO_SFN(1));
 tmp = readl(S3C64XX_GPNDAT);
 tmp = tmp | 0x0100;
 writel(tmp,S3C64XX_GPNDAT);
 udelay(2);

 tmp = tmp & 0xfeff;
 writel(tmp,S3C64XX_GPNDAT);
 udelay(500);
 
 tmp = tmp | 0x0100;
 writel(tmp,S3C64XX_GPNDAT);
 udelay(60);

 s3c_gpio_cfgpin(ds18b20_table[0],S3C_GPIO_SFN(0));
 tmp = readl(S3C64XX_GPNDAT);
 val = tmp & 0x0100;
 udelay(500);

 s3c_gpio_cfgpin(ds18b20_table[0],S3C_GPIO_SFN(1));
 tmp = readl(S3C64XX_GPNDAT);
 tmp = tmp | 0x0100;
 writel(tmp,S3C64XX_GPNDAT);

 return val;
}

 

 

 

2. 写时序

static void write_ds18b20(unsigned char data)
{
 unsigned tmp;
 //unsigned char tmp1;
 int i;

 s3c_gpio_cfgpin(ds18b20_table[0],S3C_GPIO_SFN(1));

 for(i = 0;i < 8;i ++)
 {
  tmp = readl(S3C64XX_GPNDAT);
  tmp = tmp | 0x0100;
  writel(tmp,S3C64XX_GPNDAT);
  udelay(2);
  tmp = tmp & 0xfeff;
  writel(tmp,S3C64XX_GPNDAT);

  if(data & 0x01)
  {
   tmp = tmp | 0x0100;
  }else
  {
   tmp = tmp & 0xfeff;  
  } 
  writel(tmp,S3C64XX_GPNDAT);
  udelay(60);

  data >>= 1;
 }

 tmp = tmp | 0x0100;
 writel(tmp,S3C64XX_GPNDAT);
 
 return;
}

 

 

 

3. 读时序

unsigned char read_ds18b20(void)
{
 unsigned tmp;
 unsigned char data;
 int i;

 data = 0;
 for(i = 0; i < 8;i ++)
 {
  s3c_gpio_cfgpin(ds18b20_table[0],S3C_GPIO_SFN(1));
  tmp = readl(S3C64XX_GPNDAT);
  tmp = tmp | 0x0100;
  writel(tmp,S3C64XX_GPNDAT);
  udelay(2);
  tmp = tmp & 0xfeff;
  writel(tmp,S3C64XX_GPNDAT);
  udelay(2);

  tmp = tmp | 0x0100;
  writel(tmp,S3C64XX_GPNDAT);
  udelay(8);
 
  data >>= 1;
  s3c_gpio_cfgpin(ds18b20_table[0],S3C_GPIO_SFN(0));
  tmp = readl(S3C64XX_GPNDAT);
  if(tmp & 0x0100)
  {
   data = data | 0x80;
  }

  udelay(50);
 }

 s3c_gpio_cfgpin(ds18b20_table[0],S3C_GPIO_SFN(1)); 
 tmp = readl(S3C64XX_GPNDAT);
 tmp = tmp | 0x0100;
 writel(tmp,S3C64XX_GPNDAT);

 return data;
}

 

 

 

 

4.执行序列

unsigned int result[2];
 unsigned int ret;

 ret = init_ds18b20();
 if(ret)
 {
  printk("reset error!\n");
  return -1;
 }

// write_data(0);
 write_ds18b20(0xcc);
 write_ds18b20(0x44);
// mdelay(800);

 ret = init_ds18b20();
 if(ret)
 {
  printk("reset error!\n");
  return -1;
 }
 write_ds18b20(0xcc);
 write_ds18b20(0xbe);

 result[0] = read_ds18b20();
 result[1] = read_ds18b20();

// printk("%x,%x\n",result[0],result[1]); 
 result[1] <<= 8;
 result[0] = result[0] | result[1];