Adafruit_AM2315.cpp

/*************************************************** 
  This is a library for the AM2315 Humidity & Temp Sensor

  Designed specifically to work with the AM2315 sensor from Adafruit
  ----> https://www.adafruit.com/products/1293

  These displays use I2C to communicate, 2 pins are required to  
  interface
  Adafruit invests time and resources providing this open source code, 
  please support Adafruit and open-source hardware by purchasing 
  products from Adafruit!

  Written by Limor Fried/Ladyada for Adafruit Industries.  
  BSD license, all text above must be included in any redistribution
 ****************************************************/

#include "Adafruit_AM2315.h"
#if defined(__AVR__)
  #include <util/delay.h>
#endif

Adafruit_AM2315::Adafruit_AM2315() {
}


boolean Adafruit_AM2315::begin(void) {
  Wire.begin();
  
   // try to read data, as a test
  return readData();
}

boolean Adafruit_AM2315::readData(void) {
  uint8_t reply[10];
  
  // Wake up the sensor
  Wire.beginTransmission(AM2315_I2CADDR);
  delay(2);
  Wire.endTransmission();

  // OK lets ready!
  Wire.beginTransmission(AM2315_I2CADDR);
  Wire.write(AM2315_READREG);
  Wire.write(0x00);  // start at address 0x0
  Wire.write(4);  // request 4 bytes data
  Wire.endTransmission();
  
  delay(10); // add delay between request and actual read!

  Wire.requestFrom(AM2315_I2CADDR, 8);
  for (uint8_t i=0; i<8; i++) {
    reply[i] = Wire.read();
    //Serial.println(reply[i], HEX);
  }
  
  if (reply[0] != AM2315_READREG) return false;
  if (reply[1] != 4) return false; // bytes req'd
  
  humidity = reply[2];
  humidity *= 256;
  humidity += reply[3];
  humidity /= 10;
  //Serial.print("H"); Serial.println(humidity);

  temp = reply[4] & 0x7F;
  temp *= 256;
  temp += reply[5];
  temp /= 10;
  //Serial.print("T"); Serial.println(temp);

  // change sign
  if (reply[4] >> 7) temp = -temp;

  return true;
}


float Adafruit_AM2315::readTemperature(void) {
  if (! readData()) return NAN;
  return temp;
}

float Adafruit_AM2315::readHumidity(void) {
  if (! readData()) return NAN;
  return humidity;
}


/*
 * This method returns both temperature and humidity in a single call and using a single I2C request. 
 *
 * If you want to obtain both temperature and humidity when you sample the sensor, be aware that calling 
 * readTemperature() and readHumidity() in rapid succession may swamp the sensor and result in invalid 
 * readingings (the AM2315 manual advisess that continuous samples must be at least 2 seconds apart).
 * Calling this method avoids the double I2C request.
 */
bool Adafruit_AM2315::readTemperatureAndHumidity(float &t, float &h) {
    if (!readData()) return false;
    
    t = temp;
    h = humidity;
    
    return true;
}

/*********************************************************************/