DHT22.cpp

00001 #include "DHT22.h"
00002 
00003 
00004 DHT22::DHT22(PinName pin) {
00005     _data_pin = pin;
00006 }
00007 
00008 int DHT22::getTemperature() {
00009     return _temperature;
00010 }
00011 
00012 int DHT22::getHumidity() {
00013     return _humidity;
00014 }
00015 
00016 bool DHT22::sample() {
00017     DigitalInOut DHT22(_data_pin);
00018     int dht22_dat [5];
00019     
00020     DHT22.output();
00021     DHT22.write(0);
00022     wait_ms(18);
00023     
00024     DHT22.write(1);
00025     DHT22.input();
00026     wait_us(40);
00027     wait_us(80);
00028     int i,j,result=0;
00029     
00030     for (i=0; i<5; i++) {
00031         result=0;
00032         for (j=0; j<8; j++) {
00033             while (DHT22);
00034             while (!DHT22);
00035             wait_us(50);
00036             int p;
00037             p=DHT22;
00038             p=p <<(7-j);
00039             result=result|p;
00040         }
00041         dht22_dat[i] = result;
00042     }
00043     int dht22_check_sum;
00044     dht22_check_sum=dht22_dat[0]+dht22_dat[1]+dht22_dat[2]+dht22_dat[3];
00045     dht22_check_sum= dht22_check_sum%256;
00046     if (dht22_check_sum==dht22_dat[4]) {
00047         _humidity=dht22_dat[0]*256+dht22_dat[1];
00048         _temperature=dht22_dat[2]*256+dht22_dat[3];
00049         return true;
00050     }
00051     return false;
00052 }