1 //
  2 //    FILE: dht.cpp
  3 // VERSION: 0.1.01
  4 // PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
  5 //
  6 // DATASHEET:
  7 //
  8 // HISTORY:
  9 // 0.1.01 added support for Arduino 1.0, fixed typos (31/12/2011)
 10 // 0.1.0 by Rob Tillaart (01/04/2011)
 11 // inspired by DHT11 library
 12 //
 13
 14 #include "dht.h"
 15
 16 #define TIMEOUT 10000
 17
 18 /////
 19 //
 20 // PUBLIC
 21 //
 22
 23
 24 // return values:
 25 //  0 : OK
 26 // -1 : checksum error
 27 // -2 : timeout
 28 int dht::read11(uint8_t pin)
 29 {
 30     // READ VALUES
 31     int rv = read(pin);
 32     if (rv != 0) return rv;
 33
 34     // CONVERT AND STORE
 35     humidity    = bits[0];  // bit[1] == 0;
 36     temperature = bits[2];  // bits[3] == 0;
 37
 38     // TEST CHECKSUM
 39     uint8_t sum = bits[0] + bits[2]; // bits[1] && bits[3] both 0
 40     if (bits[4] != sum) return -1;
 41
 42     return 0;
 43 }
 44
 45 // return values:
 46 //  0 : OK
 47 // -1 : checksum error
 48 // -2 : timeout
 49 int dht::read22(uint8_t pin)
 50 {
 51     // READ VALUES
 52     int rv = read(pin);
 53     if (rv != 0) return rv;
 54
 55     // CONVERT AND STORE
 56     humidity    = word(bits[0], bits[1]) * 0.1;
 57
 58     int sign = 1;
 59     if (bits[2] & 0x80) // negative temperature
 60     {
 61         bits[2] = bits[2] & 0x7F;
 62         sign = -1;
 63     }
 64     temperature = sign * word(bits[2], bits[3]) * 0.1;
 65
 66
 67     // TEST CHECKSUM
 68     uint8_t sum = bits[0] + bits[1] + bits[2] + bits[3];
 69     if (bits[4] != sum) return -1;
 70
 71     return 0;
 72 }
 73
 74 /////
 75 //
 76 // PRIVATE
 77 //
 78
 79 // return values:
 80 //  0 : OK
 81 // -2 : timeout
 82 int dht::read(uint8_t pin)
 83 {
 84     // INIT BUFFERVAR TO RECEIVE DATA
 85     uint8_t cnt = 7;
 86     uint8_t idx = 0;
 87
 88     // EMPTY BUFFER
 89     for (int i=0; i< 5; i++) bits[i] = 0;
 90
 91     // REQUEST SAMPLE
 92     pinMode(pin, OUTPUT);
 93     digitalWrite(pin, LOW);
 94     delay(20);
 95     digitalWrite(pin, HIGH);
 96     delayMicroseconds(40);
 97     pinMode(pin, INPUT);
 98
 99     // GET ACKNOWLEDGE or TIMEOUT
100     unsigned int loopCnt = TIMEOUT;
101     while(digitalRead(pin) == LOW)
102         if (loopCnt-- == 0) return -2;
103
104     loopCnt = TIMEOUT;
105     while(digitalRead(pin) == HIGH)
106         if (loopCnt-- == 0) return -2;
107
108     // READ THE OUTPUT - 40 BITS => 5 BYTES
109     for (int i=0; i<40; i++)
110     {
111         loopCnt = TIMEOUT;
112         while(digitalRead(pin) == LOW)
113             if (loopCnt-- == 0) return -2;
114
115         unsigned long t = micros();
116
117         loopCnt = TIMEOUT;
118         while(digitalRead(pin) == HIGH)
119             if (loopCnt-- == 0) return -2;
120
121         if ((micros() - t) > 40) bits[idx] |= (1 << cnt);
122         if (cnt == 0)   // next byte?
123         {
124             cnt = 7;
125             idx++;
126         }
127         else cnt--;
128     }
129
130     return 0;
131 }
132 //
133 // END OF FILE
134 //

//
//    FILE: dht.h
// VERSION: 0.1.01
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
//
//     URL: http://arduino.cc/playground/Main/DHTLib
//
// HISTORY:
// see dht.cpp file
// 

#ifndef dht_h
#define dht_h#if ARDUINO < 100
#include <WProgram.h>
#else
#include <Arduino.h>
#endif#define DHT_LIB_VERSION "0.1.01"class dht
{
public:int read11(uint8_t pin);int read22(uint8_t pin);double humidity;double temperature;private:uint8_t bits[5];  // buffer to receive dataint read(uint8_t pin);
};
#endif
//
// END OF FILE
//

//
//   FILE:  dht_test.pde
// PURPOSE: DHT library test sketch for Arduino
//

#include <dht.h>dht DHT;//这里是用class类dht 创建一个名为DHT的对象（实例）。其继承含有dht的属性与方法（面向对象开发，程序都是这么回事）上面的代码有class dht{}#define DHT11_PIN 4//put the sensor in the digital pin 4void setup()
{Serial.begin(9600);Serial.println("DHT TEST PROGRAM ");Serial.print("LIBRARY VERSION: ");Serial.println(DHT_LIB_VERSION);Serial.println();Serial.println("Type,\tstatus,\tHumidity (%),\tTemperature (C)");
}void loop()
{// READ DATASerial.print("DHT11, \t");int chk = DHT.read11(DHT11_PIN);　　　　//这里是利用库里面的一个函数read11这个函数。意思是每次输出温度、湿度的时候，都要运行。switch (chk){case 0:  Serial.print("OK,\t"); break;　　　　　　//如果能读到数据，那么就输出OK，加一个tab缩进case -1: Serial.print("Checksum error,\t"); break;　　//下面这几个是解答错误的case -2: Serial.print("Time out error,\t"); break;default: Serial.print("Unknown error,\t"); break;　　　　//default是啥也没有的时候，输出Unknown error C语言都一个样。简单明了}// DISPLAT DATASerial.print(DHT.humidity,1); //利用创建的实例的方法，输出，这里1代表输出1位精确小数，默认不写为2位Serial.print(",\t");　　　　　　//输出一个tab 缩进Serial.println(DHT.temperature,1);　　//输出对象的温度 并换行delay(1000); // 一秒一刷新新的温度，适度
}
//
// END OF FILE
//

Luckily it is trivial to connect to these sensors, they have fairly long 0.1"-pitch pins so you can plug them into any breadboard, perfboard or similar.

Likewise, it is fairly easy to connect up to the DHT sensors. They have four pins

• VCC (3 to 5V power)
• Data out
• Not connected
• Ground

Simply ignore pin 3, its not used. You will want to place a 10K resistor between VCC and the data pin, to act as a medium-strength pull up on the data line. The Arduino has built in pullups you can turn on but they're very weak, about 100K

需要在数据接口上连接一个上拉电阻。大约10k，一般是4.7k。

关于上拉电阻，下拉电阻的内容：http://www.dianyuan.com/article/213934

This diagram shows how we will connect for the testing sketch. Connect data to pin 2, you can change it later to any pin.

下面是链接方式！：