1、应用电路连接说明

2、DHT11 数据结构

humi ( 湿度 )= byte4 . byte3=45.0 ( ％RH )

temp ( 温度 )= byte2 . byte1=28.0 ( ℃ )

jiaoyan( 校验 )= byte4+ byte3+ byte2+ byte1=73(=humi+temp)( 校验正确 )

3、DHT11的传输时序

3.1  DHT11 开始发送数据流程

3.2  主机复位信号和 DHT11 响应信号

3.3  数字‘0’信号表示方法

3.4  数字‘1’信号表示方法

4、实例应用

4.1 硬件描述

4.2 管脚分配

/*原程序清单如下所示，本程序在 ICCAVR 6.31A 下测试通过。*/
#include <iom8v.h> 
#include <macros.h> 
typedef unsigned char U8; // defined for unsigned 8-bits integer variable 
typedef signed char S8; // defined for signed 8-bits integer variable 
typedef unsigned int U16; // defined for unsigned 16-bits integer variable 
typedef signed int S16; // defined for signed 16-bits integer variable 
typedef unsigned long U32; // defined for unsigned 32-bits integer variable 
typedef signed long S32; // defined for signed 32-bits integer variable 
typedef float F32; // single precision floating point variable (32bits) 
typedef double F64; // double precision floating point variable (64bits) 
/************************************************************************** 
 数码管显示赋值区
***************************************************************************/ 
#define _a 0x01 
#define _b 0x02 
#define _c 0x04 
#define _d 0x08 
#define _e 0x10 
#define _f 0x20 
#define _g 0x40 
#define _dp 0x80 
#define num0 _g //灭的数码管
#define num1 _a|_d|_e|_f|_g 
#define num2 _c|_f 
#define num3 _e|_f 
#define num4 _a|_d|_e 
#define num5 _b|_e 
#define num6 _b 
#define num7 _d|_e|_f|_g 
#define num8 0x00 
#define num9 _e 
#define num_ _a|_b|_c|_d|_e|_f|_dp
#define num_11 _a|_d|_e|_f 
#define num_E _b|_c|_dp // Err 代码
#define num_r _a|_b|_c|_d|_f|_dp 
#define dc2 0x04 
#define dc3 0x08 
#define dd 0x03 
#define dd4 0x10 
#define dd5 0x20 
#define dd6 0x40 
#define dd7 0x80 
#define dd2 0x04 
#define dd3 0x08 //数码管控制端口
#define led1 dc3 //使用时要先将数码管全熄灭掉
#define led2 dd5 
#define led3 dd4 
#define led4 dd7 
#define led5 dd6 
#define led6 dd2
U8 PLAY[6]={0,0,0,0,0,0}; 
unsigned char Flag = 0; 
unsigned int u16ReadDownStreamTimer; 
const U8 LED[14]={num0,num1,num2,num3,num4,num5,num6,num7,num8,num9, 
num_,num_11,num_E,num_r }; //数码管笔形码数组
//函数声明：
void init_devices(void); 
void time1_start(void); 
void port_init(void); 
void timer0_init(void); 
void timer1_init(void); 
void Delay(unsigned int i); 
void DelayNS (U16 dly) ; 
//***************************************************************************** 
// 显示模块
//***************************************************************************** 
void Display (void) 
 { 
 U8 i; 
 for(i=0;i<=5;i++) 
  { 
   DDRD |= 0XFC; 
   PORTD&=0x03;
   DDRC |= 0X0C; 
   PORTC&=0xF3; 
   Delay(10); 
   switch(i) 
   { 
    case 0: PORTC|=led1;break; 
    case 1: PORTD|=led2;break; 
    case 2: PORTD|=led3;break; 
    case 3: PORTD|=led4;break; 
    case 4: PORTD|=led5;break; 
    case 5: PORTD|=led6;break; 
    default :break; 
   } 
  PORTB=LED[PLAY[i]] ; //送数据 
  if((i==0)|(i==2)|(i==3)|(i==5)) //消小数点
   { 
    PORTB|=0x80; 
   } 
   DelayNS(1); 
  } 
  PORTD&=0x03; 
  PORTC&=0xF3; 
 } 
//***************************************************************************** 
// delay() 
//*****************************************************************************
void DelayNS (U16 dly) //延时子程序 1.010ms 
 { 
  U16 i; 
  for ( ; dly>0; dly--)WDR(); 
  for (i=0; i<1131; i++); 
 } 
void Delay(unsigned int i) 
 { 
  while(i--); 
 } 
void delay1N(unsigned int Dcount) 
{ 
 while(Dcount--) 
 { 
 NOP();NOP();NOP(); 
 } 
} 
void Timer2_Delay150ms(void) // Timer 2
{ 
 TCCR2 = 0x00; 
 TCNT2 = 0xDE; 
 TIFR |= 0X40; 
 TCCR2 = 0x02; 
 } 
//***************************************************************************** 
// 系统初始化函数
//***************************************************************************** 
void init_devices(void) 
 { 
  CLI(); 
  port_init(); 
  timer0_init(); 
  TIMSK = 0x05; 
  SEI(); 
 } 
//***************************************************************************** 
// 端口初始化
//***************************************************************************** 
void port_init(void) 
 { 
  DDRB = 0xFF; 
  PORTB = 0x00; 
  DDRC = 0x0C; 
  PORTC = 0x03; 
  DDRD = 0xF0; 
  PORTD = 0x00; 
} 
//***************************************************************************** 
//TIMER0 initialize - prescale:256 
// desired value: 1mSec 
// actual value: 0.992mSec (0.8%) 
//***************************************************************************** 
void timer0_init(void) 
{ 
 TCCR0 = 0x00; 
 TCNT0 = 0xE1; 
 TCCR0 = 0x04; 
} 
//***************************************************************************** 
//TIMER2 initialize - prescale:8 
// WGM: Normal 
// desired value: 35uSec
// actual value: 34.000uSec (2.9%) 
//***************************************************************************** 
void timer2_init(void) 
{ 
 TCCR2 = 0x00; 
 ASSR = 0x00; 
 TCNT2 = 0xDE; 
 OCR2 = 0x22; 
 TCCR2 = 0x02; 
} 
//***************************************************************************** 
// 定时器 TIMER0 中断
//***************************************************************************** 
#pragma interrupt_handler timer0_ovf_isr:10 
void timer0_ovf_isr(void) 
{ 
 TCNT0 = 0xE1; 
 u16ReadDownStreamTimer++; 
} 
//***************************************************************************** 
// main() function 
//***************************************************************************** 
void main(void) 
 { 
 U16 u16Flag; // 超时计数
 unsigned char iiii; 
 unsigned long u32I; // 接收数据临时变量
 unsigned long ReceiveValue = 0; // 接收数据包变量
 unsigned long ReceiveValue1 = 0; // 接收校验和变量
 unsigned int ReceiveHighByte; // 分解数据包 湿度
 unsigned int ReceiveLowByte; // 分解数据包 温度
 WDR(); 
 DelayNS(2); //提高稳定性的延时
 init_devices(); 
 timer2_init(); 
 u16ReadDownStreamTimer = 0; 
 DDRC &= ~0X20; 
 PORTC |= 0X20; 
 while(1) 
 { 
  Display(); //显示
  WDR(); 
  if(u16ReadDownStreamTimer > 1000) //1s 采集一次
 {
 if(iiii == 0) 
 { 
  DDRC |= 0X20; 
  PORTC &= ~0X20; //发送 0 
  iiii++; 
  u16ReadDownStreamTimer = 991; 
 } 
 else 
 { 
  iiii = 0; 
  delay1N(200); //延时等待对方响应 
  DDRC &= ~0X20; //输入
  PORTC |= 0X20; //拉高
  delay1N(40); //延时等待对方响应 
 if(!(PINC&0X20)) //检测对方是否响应
 { 
  u16Flag = 0; 
  while((!(PINC&0X20)) && ((u16Flag++)<50000)); 
//等待响应低电平拉高, 拉高之后开始传输数据
  ReceiveValue = 0; 
  ReceiveValue1 = 0; 
  u16Flag = 0; 
  while((PINC&0X20) && ((u16Flag++)<50000)); 
// 等待数据 第一个'0'出现
 for(u32I=0x80000000; u32I>0; u32I>>=1) 
 // 4 个字节的数据 湿度(8+8)+温度(8+8)=32(Bit) 
 { 
  u16Flag = 0; 
  while((!(PINC&0X20))&& ((u16Flag++)<30)); 
  Timer2_Delay150ms(); 
  u16Flag = 0; 
  while((PINC&0X20) && ((u16Flag++)<300)); 
  if(TIFR&0x40) 
 { 
  ReceiveValue |= u32I; 
 } 
 } 
  for(u32I=0x80; u32I>0; u32I>>=1) // 1 BYTE 的校验字节
 { 
  u16Flag = 0; 
  while((!(PINC&0X20))&& ((u16Flag++)<30)); 
  Timer2_Delay150ms(); 
  u16Flag = 0; 
  while((PINC&0X20) && ((u16Flag++)<300));
if(TIFR&0x40) 
 { 
  ReceiveValue1 |= u32I; 
 } 
 } 
 DDRC |= 0X20; //输出
 PORTC |= 0X20; //高上拉
 ReceiveLowByte =(unsigned int )( ReceiveValue&0x0000FFFF); 
 ReceiveHighByte = ReceiveValue>>16; 
 if((U8)(*((U8*)(&ReceiveHighByte)+1)+*((U8*)(&ReceiveLowByte)+1)) 
==*(U8 *)(&ReceiveValue1)) 
 { //校验和
  PLAY[3] = *((U8*)(&ReceiveHighByte) + 1)/10; 
  PLAY[4] = *((U8*)(&ReceiveHighByte) + 1)%10; 
  PLAY[2] = 0; 
  PLAY[0] = *((U8*)(&ReceiveLowByte) + 1)/10; 
  PLAY[1] = *((U8*)(&ReceiveLowByte) + 1)%10; 
  PLAY[5] = 0; 
 } 
 else //校验和不正确显示 6 个 8 
 { 
  PLAY[0] = 8; PLAY[1] = 8; 
  PLAY[2] = 8; PLAY[3] = 8; 
  PLAY[4] = 8; PLAY[5] = 8; 
 } 
 } 
 else //没有检测到信号 发送 Err 到显示
 { 
  PLAY[0] = 12;PLAY[1] = 13;PLAY[2] = 13; 
  PLAY[3] = 12;PLAY[4] = 13;PLAY[5] = 13; 
 } 
 DDRC |= 0X20; 
 PORTC |= 0X20; 
 u16ReadDownStreamTimer = 0; //清定时计数位
  } 
 } 
 else // 还没到，等待
  { 
  DelayNS(1);DelayNS(1); 
  DelayNS(1);DelayNS(1); 
   } 
  } 
 }