DS18B20程序

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#define CLR_DIR_1WIRE DDRD&=~BIT(4)    //只要修改这里的参数就可以了！呵呵！
#define SET_DIR_1WIRE DDRD|=BIT(4)      //里面什么都不用该！
#define CLR_OP_1WIRE PORTD&=~BIT(4)
#define SET_OP_1WIRE PORTD|=BIT(4)
#define CHECK_IP_1WIRE (PIND&0x10)    //检测
unsigned char wmh,wml;
void init_1820()
{
    SET_DIR_1WIRE;                //设置PC2 为输出
    SET_OP_1WIRE;
    CLR_OP_1WIRE;
    delay_nus(480);    //480us以上
    SET_OP_1WIRE;
    CLR_DIR_1WIRE;
    delay_nus(20);    //15~60us
    while(CHECK_IP_1WIRE);
    SET_DIR_1WIRE;
    SET_OP_1WIRE;
    delay_nus(140); //60~240us
}
void write_1820(unsigned char x)
{
    unsigned char m;
    for(m=0;m<8;m++)
    {
      CLR_OP_1WIRE;
      if(x&(1<<m))    //写数据了，先写低位的！
      SET_OP_1WIRE;
      else
      {CLR_OP_1WIRE;}
      delay_nus(40); //15~60us
      SET_OP_1WIRE;
    }
    SET_OP_1WIRE;
}
unsigned char read_1820()
{
    unsigned char temp,k,n;
    temp=0;
    for(n=0;n<8;n++)
      {
      CLR_OP_1WIRE;
      SET_OP_1WIRE;
      CLR_DIR_1WIRE;
      k=(CHECK_IP_1WIRE);    //读数据,从低位开始
      if(k)
      temp|=(1<<n);
      else
      temp&=~(1<<n);
      delay_nus(50); //60~120us
      SET_DIR_1WIRE;
}
return (temp);
}

void gettemp()                  //读取温度值
{
    unsigned char temh,teml,wm0,wm1,wm2,wm3;
    init_1820();        //复位18b20
    write_1820(0xcc); // 发出转换命令
    write_1820(0x44);
// delay_nms(800);    //不延时也好使，不知道怎么回事！
    init_1820();
    write_1820(0xcc); //发出读命令
    write_1820(0xbe);
    teml=read_1820(); //读数据
    temh=read_1820();
    wm0=teml>>4;      //只要高8位的低四位和低8位的高四位，温度范围0~99啦！
    wm1=temh<<4;
    wm2=wm1+wm0;        //16进制转10进制
    wm3=wm2/100;
    wmh=(wm2%100)/10; //出口参数了！wmh是显示的高位，wml使显示的低位
    wml=(wm2%100)%10;
}