求助 DHT11测量湿度不正常

只看该作者 · 2010-10-23 15:30

各位老师，我对温度湿度进行测量，使用数字温湿度传感器DHT11，显示测量值时发现一上电湿度数值就不停跳动，跳动数值幅度有十几，温度数值基本没变，感觉测量湿度数值不正确，请各位帮忙指导下，谢谢。
程序如下，MCU为16F873，晶振为10MHz
#include "pic.h"
#define uchar unsigned char
#define uint unsigned int
#define LCD_RS RC5
#define LCD_RW RC6
#define LCD_EN RC7
#define DH RC4 //定义DHT11数据端口
#define DH_HIGH() TRISC4=1 //设置数据口为输入
#define DH_LOW() TRISC4=0;DH = 0 //设置数据口为输出
uchar RH_data_H_temp,RH_data_L_temp,T_data_H_temp,T_data_L_temp,checkdata_temp;
uchar RH_data_H,RH_data_L,T_data_H,T_data_L,checkdata;
uchar flag,temp,comdata;

void delayus(uint x,uchar y)
{ uint i; uchar j;
for(i=x;i>0;i--);
for(j=y;j>0;j--);
}

void COM()
{ uchar i;
for(i=0;i<8;i++)
{ flag=2;
   while((!(DH))&&flag++);//等待高电平
      if(flag==1)break;
         delayus(0,2);
         delayus(0,2);
         delayus(0,2);
         //delayus(0,2);
         temp=0;
         if(DH)temp=1;
         flag=2;
         while((DH)&&flag++); //等待低电平
         //超时则跳出for循环
         if(flag==1)break;
         //判断数据位是0还是1 // 如果高电平高过预定0高电平值则数据位为 1
         comdata<<=1;
         comdata|=temp; //0
      }
}
//--------------------------------
//-----湿度读取子程序 ------------
//--------------------------------
//----以下变量均为全局变量--------
//----温度高8位== U8T_data_H------
//----温度低8位== U8T_data_L------
//----湿度高8位== U8RH_data_H-----
//----湿度低8位== U8RH_data_L-----
//----校验 8位 == U8checkdata-----
//--------------------------------
void RH(void)
{ //主机拉低18ms
   DH_LOW();
   delayus(5000,200);
   DH_HIGH(); //总线由上拉电阻拉高主机延时20-40us
   delayus(0,2);
   delayus(0,2);
   delayus(0,2);
   delayus(0,2);
      //主机设为输入判断从机响应信号
   DH_HIGH();
      //判断从机是否有低电平响应信号如不响应则跳出，响应则向下运行
      if(!DH)
      {    flag=2;
            //判断从机是否发出 80us 的低电平响应信号是否结束
            while((!(DH))&&flag++);
            flag=2;
            //判断从机是否发出 80us 的高电平，如发出则进入数据接收状态
            while((DH)&&flag++);
            //数据接收状态
            COM();
            RH_data_H_temp=comdata;
            COM();
            RH_data_L_temp=comdata;
            COM();
            T_data_H_temp=comdata;
            COM();
            T_data_L_temp=comdata;
            COM();
            checkdata_temp=comdata;
            DH_HIGH();
            //数据校验
            temp=(T_data_H_temp+T_data_L_temp+RH_data_H_temp+RH_data_L_temp);
            if(temp==checkdata_temp)
            { RH_data_H=RH_data_H_temp;
                  RH_data_L=RH_data_L_temp;
                  T_data_H=T_data_H_temp;
                  T_dataL=T_data_L_temp;
                  checkdata=checkdata_temp;
            }

      } //fi

}

void Delayms(uint ms)
{  uchar i;
while(ms--)
{ for(i=0;i<120;i++);
   }
}

--------------下面为液晶模块程序--------
uchar LCD_Busy_Check()
{ uchar result;
TRISB=0xFF;
LCD_RS = 0;
LCD_RW = 1;
LCD_EN = 1;
Delayms(1);
result=PORTB;
LCD_EN=0;
return result;
}

void Write_LCD_Command(uchar cmd)
{ while((LCD_Busy_Check()&0x80)==0x80);
TRISB=0x00;
LCD_RS = 0;
LCD_RW = 0;
LCD_EN = 0;
PORTB=cmd;
LCD_EN = 1;
Delayms(1);
LCD_EN = 0;
}

void Write_LCD_Data(uchar dat)
{ while((LCD_Busy_Check()&0x80)==0x80);
TRISB=0x00;
LCD_RS" = 1;
LCD_RW = 0;
LCD_EN = 0;
PORTB = dat;
LCD_EN = 1;
Delayms(1);
LCD_EN = 0;
}

void LCD_Initialise()
{ Write_LCD_Command(0x01);
Delayms(1);
Write_LCD_Command(0x38);
Delayms(1);
Write_LCD_Command(0x0c);
Delayms(1);
Write_LCD_Command(0x06);
Delayms(1);
}

void Set_LCD_POS(uchar pos)
{
Write_LCD_Command(pos|0x80);
}

void init()
{ ADCON1=0x07;
TRISA=0x00;
TRISC=0x00;
}

void disp()
{  Set_LCD_POS(0x00);
Write_LCD_Data(RH_data_H/10+0x30);
Set_LCD_POS(0x01);
Write_LCD_Data(RH_data_H%10+0x30);
Set_LCD_POS(0x02);
Write_LCD_Data('%');
Set_LCD_POS(0x07);
Write_LCD_Data(T_data_H/10+0x30);
Set_LCD_POS(0x08);
Write_LCD_Data(T_data_H%10+0x30);
Set_LCD_POS(0x09);
Write_LCD_Data(0xdf);
Set_LCD_POS(0x0A);
Write_LCD_Data(0x43);
}

void main()
{ init();
LCD_Initialise();
DH_HIGH();
while(1)
   { RH();
      disp();
   }
}