[求助] 哪位高手玩过DHT11,有问题请教

whg0109 2013-12-17 10:21 楼主

调试DHT11程序两天了仍然觉得不对劲......代码如下
DHT11.C

#include
#include
#include "DHT11.H"

unsigned char DHT11_init(void){
      unsigned char i=16;
      DHT11_IO_OUT;
      DHT11_IO_SET;
      _delay_ms(1);
      DHT11_IO_CLR;
      _delay_ms(20); //主机拉低IO，并至少保持18ms
      DHT11_IO_SET;
      _delay_us(10); // 主机拉高IO 20到40us;其后器件响应 40－50us电平

      DHT11_IO_IN;
      //DHT11_IO_SET;  //带有上拉暂时注释，因为电路中已有4.7K上接电阻，以免上拉太强
      while(i--){ //每5us采样一次若采到0 说明器件响应正常，若16次以后仍未采到说明100us时间已过器件仍未应答有问题
            _delay_us(5);
            if (DHT11_IO_READ_L){
            while (DHT11_IO_READ_L){asm("nop");}  //本人程序中读到响应0即完成器件存在的判断，故器件响应的0有可能尚未结束，nop若干进行渡过
         while (DHT11_IO_READ_H){asm("nop");}  //器件响应0后会拉高IO 40-50us 后以低电平开始发数据，故渡过
                     return 1;
            }
      }
      return 0;
      //器件应答正常则返回1 否则返回0 符合日常习惯

}

unsigned char  DHT11_READ_BYTE(void){
      unsigned char i,dat=0;                   //DHT11_INIT时已将口线设为输入
      for (i=0;i<8;i++){
            while (DHT11_IO_READ_L){asm("nop");}  //渡过每个数据开始位时的低电平12－14us 其后，器件将拉高数据线，发0时保持26--28us 发1时保持116-118us
                                             //故在渡过起始0电平后的50us时进行采样若为高则是1，若为低，实际是下一位的起始0电平，仍能说明当前所发的是0
      _delay_us(50);
      if (DHT11_IO_READ_H)
      {
         dat |= 0x01;                         //手册写明，数据格式是高位先出
         while (DHT11_IO_READ_H)
         {
               asm("nop");                   //因发1时，高电平较长，nop渡过
         }
      }
      dat <<= 1;                                  //读到数据，左移1位，预备接收下一位
      }
      return dat;
}

主程序片断

  while(1)
{



            _delay_ms(255);
            _delay_ms(255);
            _delay_ms(255);
            _delay_ms(255);
            _delay_ms(255);
            _delay_ms(255);
            _delay_ms(255);
            LCD12864_WRITE_BYTE_S(0,0x01);
            DHT11_init();
            RH[0] = DHT11_READ_BYTE();
            RH[1] = DHT11_READ_BYTE();
            RH[2] = DHT11_READ_BYTE();
            RH[3] = DHT11_READ_BYTE();
            RH[4] = DHT11_READ_BYTE();
            LCD12864_WRITE_BYTE_S(0,0x88);
            LCD12864_WRITE_BYTE_S(1,RH[0]/100+0x30);
            LCD12864_WRITE_BYTE_S(1,(RH[0]%100)/10+0x30);
            LCD12864_WRITE_BYTE_S(1,(RH[0]%100)%10+0x30);

            LCD12864_WRITE_BYTE_S(1,' ');
            LCD12864_WRITE_BYTE_S(1,RH[1]/100+0x30);
            LCD12864_WRITE_BYTE_S(1,(RH[1]%100)/10+0x30);
            LCD12864_WRITE_BYTE_S(1,(RH[1]%100)%10+0x30);

            LCD12864_WRITE_BYTE_S(0,0x90);
            LCD12864_WRITE_BYTE_S(1,RH[2]/100+0x30);
            LCD12864_WRITE_BYTE_S(1,(RH[2]%100)/10+0x30);
            LCD12864_WRITE_BYTE_S(1,(RH[2]%100)%10+0x30);

            LCD12864_WRITE_BYTE_S(1,' ');
            LCD12864_WRITE_BYTE_S(1,RH[3]/100+0x30);
            LCD12864_WRITE_BYTE_S(1,(RH[3]%100)/10+0x30);
            LCD12864_WRITE_BYTE_S(1,(RH[3]%100)%10+0x30);

   LCD12864_WRITE_BYTE_S(0,0x98);
   LCD12864_WRITE_BYTE_S(1,RH[4]/100+0x30);
   LCD12864_WRITE_BYTE_S(1,(RH[4]%100)/10+0x30);
   LCD12864_WRITE_BYTE_S(1,(RH[4]%100)%10+0x30);

               if ((RH[0]+RH[1]+RH[2]+RH[3])==RH[4]){
                        LCD12864_WRITE_STR_S("check OK");
               }
               else
               LCD12864_WRITE_STR_S("Error");


程序运行结果如图
现在问题是  温度数据明显太高了，北方冬天室内怎么就有40多度

请各位指点一下，谢谢

[ 本帖最后由 whg0109 于 2013-12-17 12:08 编辑 ]