EEPW论坛

//==========================================================================//
//向18b20写数据
//==========================================================================//
void Write18B20_byte(uchar data)
{
    uchar i,dat;
    for(i=0;i<8;i++)
    {
        SysCtlPeriEnable(DQ_PERIPH);                                    //  使能GPIOB端口
        GPIOPinTypeOut(DQ_PORT , DQ_PIN);                               //  设置PB0输出类型
        GPIOPinWrite(DQ_PORT , DQ_PIN , 0x00);       //  PB0输出低电平
        Delay(18); 
        dat=data & 0x01;
        GPIOPinWrite(DQ_PORT , DQ_PIN , dat);
        GPIOPinRead(DQ_PORT , DQ_PIN);
        Delay(50); 
        GPIOPinTypeOut(DQ_PORT , DQ_PIN);
        GPIOPinWrite(DQ_PORT , DQ_PIN , 0xff);
        data>>=1;
    }
      Delay(5* (TheSysClock / 4000));   
}

//==========================================================================//
//读取18b20数据
//==========================================================================//
uchar Read18B20_byte(void)
{
     uint i;
     uchar value;
     for(i=0;i<8;i++)
     {
        SysCtlPeriEnable(DQ_PERIPH);                                    //  使能GPIOB端口
        GPIOPinTypeOut(DQ_PORT , DQ_PIN);                               //  设置PB0输出类型
        GPIOPinWrite(DQ_PORT , DQ_PIN , 0x00);       //  PB0输出低电平
        Delay(5); 
        value>>=1;
        GPIOPinWrite(DQ_PORT , DQ_PIN , 0xff);
        Delay(40);                                                              //  延时2us
        if(GPIOPinRead(DQ_PORT , DQ_PIN))
          value|=0x80;
        Delay(3 * (TheSysClock / 4000));
     }
     return (value);
}

//===========================================================================//
//18b20测温程序
//===========================================================================//
uint readtemp(void)
{
        unsigned char TemL,TemH;
        Init_DS18B20();                                                         //复位18b20
        Delay(1200);                                                        //时                                                       //延时300us
        Write18B20_byte(0xcc);                                                       //跳过ROM区域                                                          //延时10us
        Write18B20_byte(0x44);                                                       //温度转换
        Delay(1200);                                                        //延时1s
        Init_DS18B20();
        Write18B20_byte(0xcc);                                                       //跳过ROM区域                                                          //延时10us
        Write18B20_byte(0xbe);                                      
        TemL=Read18B20_byte();                                                   //读低位温度值
        TemH=Read18B20_byte();                                                   //读高位温度值
        TemH<<=4;
        TemH+=(TemL&0xf0)>>4;
        TemH=TemH*(0.0625);
        return (TemH);
}

温度传感器18b20一直显示15，这是为什么？各位大侠帮助....