DHT11 数字温湿度传感器
来自Jack's Lab
目录 |
1 概述
DHT11 Datasheet: http://www.micro4you.com/files/sensor/DHT11.pdf
2 库
//
// FILE: dht11.cpp
// VERSION: 0.4.1
// PURPOSE: DHT11 Temperature & Humidity Sensor library for Arduino
// LICENSE: GPL v3 (http://www.gnu.org/licenses/gpl.html)
//
// DATASHEET: http://www.micro4you.com/files/sensor/DHT11.pdf
//
// HISTORY:
// George Hadjikyriacou - Original version (??)
// Mod by SimKard - Version 0.2 (24/11/2010)
// Mod by Rob Tillaart - Version 0.3 (28/03/2011)
// + added comments
// + removed all non DHT11 specific code
// + added references
// Mod by Rob Tillaart - Version 0.4 (17/03/2012)
// + added 1.0 support
// Mod by Rob Tillaart - Version 0.4.1 (19/05/2012)
// + added error codes
//
#include "dht11.h"
// Return values:
// DHTLIB_OK
// DHTLIB_ERROR_CHECKSUM
// DHTLIB_ERROR_TIMEOUT
int dht11::read(int pin)
{
// BUFFER TO RECEIVE
uint8_t bits[5];
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(18);
digitalWrite(pin, HIGH);
delayMicroseconds(40);
pinMode(pin, INPUT);
// ACKNOWLEDGE or TIMEOUT
unsigned int loopCnt = 10000;
while(digitalRead(pin) == LOW)
if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
loopCnt = 10000;
while(digitalRead(pin) == HIGH)
if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
// READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT
for (int i=0; i<40; i++)
{
loopCnt = 10000;
while(digitalRead(pin) == LOW)
if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
unsigned long t = micros();
loopCnt = 10000;
while(digitalRead(pin) == HIGH)
if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
if ((micros() - t) > 40) bits[idx] |= (1 << cnt);
if (cnt == 0) // next byte?
{
cnt = 7; // restart at MSB
idx++; // next byte!
}
else cnt--;
}
// WRITE TO RIGHT VARS
// as bits[1] and bits[3] are allways zero they are omitted in formulas.
humidity = bits[0];
temperature = bits[2];
uint8_t sum = bits[0] + bits[2];
if (bits[4] != sum) return DHTLIB_ERROR_CHECKSUM;
return DHTLIB_OK;
}
//
// FILE: dht11.h
// VERSION: 0.4.1
// PURPOSE: DHT11 Temperature & Humidity Sensor library for Arduino
// LICENSE: GPL v3 (http://www.gnu.org/licenses/gpl.html)
//
// DATASHEET: http://www.micro4you.com/files/sensor/DHT11.pdf
//
// URL: http://playground.arduino.cc/Main/DHT11Lib
//
// HISTORY:
// George Hadjikyriacou - Original version
// see dht.cpp file
//
#ifndef dht11_h
#define dht11_h
#if defined(ARDUINO) && (ARDUINO >= 100)
#include <Arduino.h>
#else
#include <WProgram.h>
#endif
#define DHT11LIB_VERSION "0.4.1"
#define DHTLIB_OK 0
#define DHTLIB_ERROR_CHECKSUM -1
#define DHTLIB_ERROR_TIMEOUT -2
class dht11
{
public:
int read(int pin);
int humidity;
int temperature;
};
#endif
3 示例
//
// FILE: dht11_test1.pde
// PURPOSE: DHT11 library test sketch for Arduino
//
//Celsius to Fahrenheit conversion
double Fahrenheit(double celsius)
{
return 1.8 * celsius + 32;
}
// fast integer version with rounding
//int Celcius2Fahrenheit(int celcius)
//{
// return (celsius * 18 + 5)/10 + 32;
//}
//Celsius to Kelvin conversion
double Kelvin(double celsius)
{
return celsius + 273.15;
}
// dewPoint function NOAA
// reference (1) : http://wahiduddin.net/calc/density_algorithms.htm
// reference (2) : http://www.colorado.edu/geography/weather_station/Geog_site/about.htm
//
double dewPoint(double celsius, double humidity)
{
// (1) Saturation Vapor Pressure = ESGG(T)
double RATIO = 373.15 / (273.15 + celsius);
double RHS = -7.90298 * (RATIO - 1);
RHS += 5.02808 * log10(RATIO);
RHS += -1.3816e-7 * (pow(10, (11.344 * (1 - 1/RATIO ))) - 1) ;
RHS += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1) ;
RHS += log10(1013.246);
// factor -3 is to adjust units - Vapor Pressure SVP * humidity
double VP = pow(10, RHS - 3) * humidity;
// (2) DEWPOINT = F(Vapor Pressure)
double T = log(VP/0.61078); // temp var
return (241.88 * T) / (17.558 - T);
}
// delta max = 0.6544 wrt dewPoint()
// 6.9 x faster than dewPoint()
// reference: http://en.wikipedia.org/wiki/Dew_point
double dewPointFast(double celsius, double humidity)
{
double a = 17.271;
double b = 237.7;
double temp = (a * celsius) / (b + celsius) + log(humidity*0.01);
double Td = (b * temp) / (a - temp);
return Td;
}
#include <dht11.h>
dht11 DHT11;
#define DHT11PIN 2
void setup()
{
Serial.begin(115200);
Serial.println("DHT11 TEST PROGRAM ");
Serial.print("LIBRARY VERSION: ");
Serial.println(DHT11LIB_VERSION);
Serial.println();
}
void loop()
{
Serial.println("\n");
int chk = DHT11.read(DHT11PIN);
Serial.print("Read sensor: ");
switch (chk)
{
case DHTLIB_OK:
Serial.println("OK");
break;
case DHTLIB_ERROR_CHECKSUM:
Serial.println("Checksum error");
break;
case DHTLIB_ERROR_TIMEOUT:
Serial.println("Time out error");
break;
default:
Serial.println("Unknown error");
break;
}
Serial.print("Humidity (%): ");
Serial.println((float)DHT11.humidity, 2);
Serial.print("Temperature (°C): ");
Serial.println((float)DHT11.temperature, 2);
Serial.print("Temperature (°F): ");
Serial.println(Fahrenheit(DHT11.temperature), 2);
Serial.print("Temperature (°K): ");
Serial.println(Kelvin(DHT11.temperature), 2);
Serial.print("Dew Point (°C): ");
Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));
Serial.print("Dew PointFast (°C): ");
Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));
delay(2000);
}
4 优化版
https://github.com/adalton/arduino/tree/master/projects/Dht11_Library
5 参考
- http://playground.arduino.cc/Main/DHT11Lib
- http://www.micro4you.com/files/sensor/DHT11.pdf
- http://playground.arduino.cc/Main/DHTLib
