使用Arduino与DHT11监测温湿度

这两天开始一一测试之前买过的一些传感器，首先挑选的是DHT11，这个传感器用于粗略估计温湿度。

硬件连接很简单，只需要将DHT11传感器和数字针脚4相连，这里我用到了传感器扩展板，直接连在扩展板上。材料都是用的奥松机器人基地的。

第一件麻烦事儿就是DHT11的库文件，中文材料是木有滴，我到了官网，终于把一个可以用的库文件找出来了。这个库文件还可以测DHT22。如下两个文件，放在DHT文件夹中，然后放到ardunio的库文件夹。

dht.cpp

//
//    FILE: dht.cpp
// VERSION: 0.1.01
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
//
// DATASHEET: 
//
// HISTORY:
// 0.1.01 added support for Arduino 1.0, fixed typos (31/12/2011)
// 0.1.0 by Rob Tillaart (01/04/2011)
// inspired by DHT11 library
//

#include "dht.h"

#define TIMEOUT 10000

/
//
// PUBLIC
//


// return values:
//  0 : OK
// -1 : checksum error
// -2 : timeout
int dht::read11(uint8_t pin)
{
	// READ VALUES
	int rv = read(pin);
	if (rv != 0) return rv;

	// CONVERT AND STORE
	humidity    = bits[0];  // bit[1] == 0;
	temperature = bits[2];  // bits[3] == 0;

	// TEST CHECKSUM
	uint8_t sum = bits[0] + bits[2]; // bits[1] && bits[3] both 0
	if (bits[4] != sum) return -1;

	return 0;
}

// return values:
//  0 : OK
// -1 : checksum error
// -2 : timeout
int dht::read22(uint8_t pin)
{
	// READ VALUES
	int rv = read(pin);
	if (rv != 0) return rv;

	// CONVERT AND STORE
	humidity    = word(bits[0], bits[1]) * 0.1;

	int sign = 1;
	if (bits[2] & 0x80) // negative temperature
	{
		bits[2] = bits[2] & 0x7F;
		sign = -1;
	}
	temperature = sign * word(bits[2], bits[3]) * 0.1;


	// TEST CHECKSUM
	uint8_t sum = bits[0] + bits[1] + bits[2] + bits[3];
	if (bits[4] != sum) return -1;

	return 0;
}

/
//
// PRIVATE
//

// return values:
//  0 : OK
// -2 : timeout
int dht::read(uint8_t pin)
{
	// INIT BUFFERVAR TO RECEIVE DATA
	uint8_t cnt = 7;
	uint8_t idx = 0;

	// EMPTY BUFFER
	for (int i=0; i< 5; i++) bits[i] = 0;

	// REQUEST SAMPLE
	pinMode(pin, OUTPUT);
	digitalWrite(pin, LOW);
	delay(20);
	digitalWrite(pin, HIGH);
	delayMicroseconds(40);
	pinMode(pin, INPUT);

	// GET ACKNOWLEDGE or TIMEOUT
	unsigned int loopCnt = TIMEOUT;
	while(digitalRead(pin) == LOW)
		if (loopCnt-- == 0) return -2;

	loopCnt = TIMEOUT;
	while(digitalRead(pin) == HIGH)
		if (loopCnt-- == 0) return -2;

	// READ THE OUTPUT - 40 BITS => 5 BYTES
	for (int i=0; i<40; i++)
	{
		loopCnt = TIMEOUT;
		while(digitalRead(pin) == LOW)
			if (loopCnt-- == 0) return -2;

		unsigned long t = micros();

		loopCnt = TIMEOUT;
		while(digitalRead(pin) == HIGH)
			if (loopCnt-- == 0) return -2;

		if ((micros() - t) > 40) bits[idx] |= (1 << cnt);
		if (cnt == 0)   // next byte?
		{
			cnt = 7;   
			idx++;      
		}
		else cnt--;
	}

	return 0;
}
//
// END OF FILE
//

dht.h

// 
//    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 
#else
#include 
#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 data
	int read(uint8_t pin);
};
#endif
//
// END OF FILE
//

库文件搞定之后，可以开始写ardunio程序了。这里因为只有DHT11，所以程序就不去测试22了。引入dht的库，然后编写如下代码：

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

#include 

dht DHT;

#define DHT11_PIN 4//put the sensor in the digital pin 4


void setup()
{
  Serial.begin(115200);
  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 DATA
  Serial.print("DHT11, \t");
 int chk = DHT.read11(DHT11_PIN);
  switch (chk)
  {
    case 0:  Serial.print("OK,\t"); break;
    case -1: Serial.print("Checksum error,\t"); break;
    case -2: Serial.print("Time out error,\t"); break;
    default: Serial.print("Unknown error,\t"); break;
  }
 // DISPLAT DATA
  Serial.print(DHT.humidity,1);
  Serial.print(",\t");
  Serial.println(DHT.temperature,1);

  delay(1000);
}
//
// END OF FILE
//

如果在控制台，出现了time out error，那么就是没读到数据，可能是引脚接错了。记得，我现在接的是数字引脚4。结果：