2011-06-21 03:47:50 +04:00
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/* DHT library
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MIT license
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written by Adafruit Industries
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*/
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2011-06-22 21:11:06 +04:00
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#include "DHT.h"
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2012-12-29 22:14:51 +04:00
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DHT::DHT(uint8_t pin, uint8_t type, uint8_t count) {
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2011-06-22 21:11:06 +04:00
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_pin = pin;
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_type = type;
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2012-12-29 22:14:51 +04:00
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_count = count;
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2011-06-22 21:11:06 +04:00
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firstreading = true;
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}
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void DHT::begin(void) {
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// set up the pins!
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pinMode(_pin, INPUT);
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digitalWrite(_pin, HIGH);
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_lastreadtime = 0;
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}
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2012-02-23 07:26:16 +04:00
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//boolean S == Scale. True == Farenheit; False == Celcius
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float DHT::readTemperature(bool S) {
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2011-06-22 21:11:06 +04:00
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float f;
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if (read()) {
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switch (_type) {
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case DHT11:
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f = data[2];
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2012-02-23 07:26:16 +04:00
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if(S)
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f = convertCtoF(f);
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2011-06-22 21:11:06 +04:00
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return f;
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case DHT22:
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case DHT21:
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f = data[2] & 0x7F;
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f *= 256;
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f += data[3];
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f /= 10;
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if (data[2] & 0x80)
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f *= -1;
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2012-02-23 07:26:16 +04:00
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if(S)
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f = convertCtoF(f);
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2011-06-22 21:11:06 +04:00
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return f;
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}
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}
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Serial.print("Read fail");
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return NAN;
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}
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2012-02-23 07:26:16 +04:00
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float DHT::convertCtoF(float c) {
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return c * 9 / 5 + 32;
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}
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2011-06-22 21:11:06 +04:00
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float DHT::readHumidity(void) {
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float f;
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if (read()) {
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switch (_type) {
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case DHT11:
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f = data[0];
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return f;
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case DHT22:
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case DHT21:
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f = data[0];
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f *= 256;
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f += data[1];
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f /= 10;
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return f;
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}
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}
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Serial.print("Read fail");
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return NAN;
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}
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2014-06-02 23:54:54 +04:00
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float DHT::computeHeatIndex(float tempFahrenheit, float percentHumidity) {
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// Adapted from equation at: https://github.com/adafruit/DHT-sensor-library/issues/9 and
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// Wikipedia: http://en.wikipedia.org/wiki/Heat_index
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return -42.379 +
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2.04901523 * tempFahrenheit +
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10.14333127 * percentHumidity +
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-0.22475541 * tempFahrenheit*percentHumidity +
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-0.00683783 * pow(tempFahrenheit, 2) +
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-0.05481717 * pow(percentHumidity, 2) +
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0.00122874 * pow(tempFahrenheit, 2) * percentHumidity +
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0.00085282 * tempFahrenheit*pow(percentHumidity, 2) +
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-0.00000199 * pow(tempFahrenheit, 2) * pow(percentHumidity, 2);
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}
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2011-06-22 21:11:06 +04:00
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boolean DHT::read(void) {
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uint8_t laststate = HIGH;
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uint8_t counter = 0;
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uint8_t j = 0, i;
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unsigned long currenttime;
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// pull the pin high and wait 250 milliseconds
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digitalWrite(_pin, HIGH);
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delay(250);
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currenttime = millis();
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if (currenttime < _lastreadtime) {
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// ie there was a rollover
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_lastreadtime = 0;
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}
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if (!firstreading && ((currenttime - _lastreadtime) < 2000)) {
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return true; // return last correct measurement
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//delay(2000 - (currenttime - _lastreadtime));
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}
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firstreading = false;
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/*
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Serial.print("Currtime: "); Serial.print(currenttime);
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Serial.print(" Lasttime: "); Serial.print(_lastreadtime);
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*/
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_lastreadtime = millis();
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data[0] = data[1] = data[2] = data[3] = data[4] = 0;
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// now pull it low for ~20 milliseconds
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pinMode(_pin, OUTPUT);
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digitalWrite(_pin, LOW);
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delay(20);
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cli();
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digitalWrite(_pin, HIGH);
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delayMicroseconds(40);
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pinMode(_pin, INPUT);
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// read in timings
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for ( i=0; i< MAXTIMINGS; i++) {
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counter = 0;
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while (digitalRead(_pin) == laststate) {
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counter++;
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delayMicroseconds(1);
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if (counter == 255) {
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break;
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}
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}
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laststate = digitalRead(_pin);
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if (counter == 255) break;
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// ignore first 3 transitions
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if ((i >= 4) && (i%2 == 0)) {
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// shove each bit into the storage bytes
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data[j/8] <<= 1;
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2012-12-29 22:14:51 +04:00
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if (counter > _count)
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2011-06-22 21:11:06 +04:00
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data[j/8] |= 1;
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j++;
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}
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}
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sei();
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/*
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Serial.println(j, DEC);
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Serial.print(data[0], HEX); Serial.print(", ");
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Serial.print(data[1], HEX); Serial.print(", ");
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Serial.print(data[2], HEX); Serial.print(", ");
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Serial.print(data[3], HEX); Serial.print(", ");
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Serial.print(data[4], HEX); Serial.print(" =? ");
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Serial.println(data[0] + data[1] + data[2] + data[3], HEX);
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*/
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// check we read 40 bits and that the checksum matches
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if ((j >= 40) &&
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(data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) ) {
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return true;
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}
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return false;
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}
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