Stefan Nielsen / DHT22

Library for reading data from the RHT03 / DHT22 digital humidity & temperature sensor.

Dependents:   Pachube-v2_DHT22 DHT_TEST2 DHT_CANSAT Projeto_Monit_Remoto ... more

DHT22.cpp@0:7fd3ff04ae95, 2011-10-27 (annotated)

Committer:
Julepalme
Date:
Thu Oct 27 15:11:06 2011 +0000
Revision:
0:7fd3ff04ae95
First Draft

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Julepalme 0:7fd3ff04ae95 1 #include "DHT22.h"
Julepalme 0:7fd3ff04ae95 2
Julepalme 0:7fd3ff04ae95 3
Julepalme 0:7fd3ff04ae95 4 DHT22::DHT22(PinName pin) {
Julepalme 0:7fd3ff04ae95 5 _data_pin = pin;
Julepalme 0:7fd3ff04ae95 6 }
Julepalme 0:7fd3ff04ae95 7
Julepalme 0:7fd3ff04ae95 8 int DHT22::getTemperature() {
Julepalme 0:7fd3ff04ae95 9 return _temperature;
Julepalme 0:7fd3ff04ae95 10 }
Julepalme 0:7fd3ff04ae95 11
Julepalme 0:7fd3ff04ae95 12 int DHT22::getHumidity() {
Julepalme 0:7fd3ff04ae95 13 return _humidity;
Julepalme 0:7fd3ff04ae95 14 }
Julepalme 0:7fd3ff04ae95 15
Julepalme 0:7fd3ff04ae95 16 bool DHT22::sample() {
Julepalme 0:7fd3ff04ae95 17 DigitalInOut DHT22(_data_pin);
Julepalme 0:7fd3ff04ae95 18 int dht22_dat [5];
Julepalme 0:7fd3ff04ae95 19 DHT22.output();
Julepalme 0:7fd3ff04ae95 20 DHT22.write(0);
Julepalme 0:7fd3ff04ae95 21 wait_ms(18);
Julepalme 0:7fd3ff04ae95 22 DHT22.write(1);
Julepalme 0:7fd3ff04ae95 23 DHT22.input();
Julepalme 0:7fd3ff04ae95 24 wait_us(40);
Julepalme 0:7fd3ff04ae95 25 wait_us(80);
Julepalme 0:7fd3ff04ae95 26 int i,j,result=0;
Julepalme 0:7fd3ff04ae95 27 for (i=0; i<5; i++) {
Julepalme 0:7fd3ff04ae95 28 result=0;
Julepalme 0:7fd3ff04ae95 29 for (j=0; j<8; j++) {
Julepalme 0:7fd3ff04ae95 30 while (DHT22);
Julepalme 0:7fd3ff04ae95 31 while (!DHT22);
Julepalme 0:7fd3ff04ae95 32 wait_us(50);
Julepalme 0:7fd3ff04ae95 33 int p;
Julepalme 0:7fd3ff04ae95 34 p=DHT22;
Julepalme 0:7fd3ff04ae95 35 p=p <<(7-j);
Julepalme 0:7fd3ff04ae95 36 result=result|p;
Julepalme 0:7fd3ff04ae95 37 }
Julepalme 0:7fd3ff04ae95 38 dht22_dat[i] = result;
Julepalme 0:7fd3ff04ae95 39 }
Julepalme 0:7fd3ff04ae95 40 int dht22_check_sum;
Julepalme 0:7fd3ff04ae95 41 dht22_check_sum=dht22_dat[0]+dht22_dat[1]+dht22_dat[2]+dht22_dat[3];
Julepalme 0:7fd3ff04ae95 42 dht22_check_sum= dht22_check_sum%256;
Julepalme 0:7fd3ff04ae95 43 if (dht22_check_sum==dht22_dat[4]) {
Julepalme 0:7fd3ff04ae95 44 _humidity=dht22_dat[0]*256+dht22_dat[1];
Julepalme 0:7fd3ff04ae95 45 _temperature=dht22_dat[2]*256+dht22_dat[3];
Julepalme 0:7fd3ff04ae95 46 return true;
Julepalme 0:7fd3ff04ae95 47 }
Julepalme 0:7fd3ff04ae95 48 return false;
Julepalme 0:7fd3ff04ae95 49 }