osd-contiki/examples/osd/arduino-htu21/Adafruit_HTU21DF.cpp
2015-11-29 22:34:24 +01:00

101 lines
2.2 KiB
C++

/***************************************************
This is a library for the HTU21DF Humidity & Temp Sensor
Designed specifically to work with the HTU21DF sensor from Adafruit
----> https://www.adafruit.com/products/1899
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_HTU21DF.h"
#if defined(__AVR__)
#include <util/delay.h>
#endif
Adafruit_HTU21DF::Adafruit_HTU21DF() {
}
boolean Adafruit_HTU21DF::begin(void) {
Wire.begin();
reset();
Wire.beginTransmission(HTU21DF_I2CADDR);
Wire.write(HTU21DF_READREG);
Wire.endTransmission();
Wire.requestFrom(HTU21DF_I2CADDR, 1);
return (Wire.read() == 0x2); // after reset should be 0x2
}
void Adafruit_HTU21DF::reset(void) {
Wire.beginTransmission(HTU21DF_I2CADDR);
Wire.write(HTU21DF_RESET);
Wire.endTransmission();
delay(15);
}
float Adafruit_HTU21DF::readTemperature(void) {
// OK lets ready!
Wire.beginTransmission(HTU21DF_I2CADDR);
Wire.write(HTU21DF_READTEMP);
Wire.endTransmission();
delay(50); // add delay between request and actual read!
Wire.requestFrom(HTU21DF_I2CADDR, 3);
while (!Wire.available()) {}
uint16_t t = Wire.read();
t <<= 8;
t |= Wire.read();
uint8_t crc = Wire.read();
float temp = t;
temp *= 175.72;
temp /= 65536;
temp -= 46.85;
return temp;
}
float Adafruit_HTU21DF::readHumidity(void) {
// OK lets ready!
Wire.beginTransmission(HTU21DF_I2CADDR);
Wire.write(HTU21DF_READHUM);
Wire.endTransmission();
delay(50); // add delay between request and actual read!
Wire.requestFrom(HTU21DF_I2CADDR, 3);
while (!Wire.available()) {}
uint16_t h = Wire.read();
h <<= 8;
h |= Wire.read();
uint8_t crc = Wire.read();
float hum = h;
hum *= 125;
hum /= 65536;
hum -= 6;
return hum;
}
/*********************************************************************/