146 lines
3.7 KiB
C++
146 lines
3.7 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_Soft.h"
|
|
#include <SoftwareWire.h>
|
|
#if defined(__AVR__)
|
|
#include <util/delay.h>
|
|
#endif
|
|
|
|
/**
|
|
* Constructor for the HTU21DF driver.
|
|
*/
|
|
Adafruit_HTU21DF_Soft::Adafruit_HTU21DF_Soft()
|
|
{
|
|
/* Assign default values to internal tracking variables. */
|
|
_last_humidity = 0.0f;
|
|
_last_temp = 0.0f;
|
|
}
|
|
|
|
/**
|
|
* Initialises the I2C transport, and configures the IC for normal operation.
|
|
*
|
|
* @return true (1) if the device was successfully initialised, otherwise
|
|
* false (0).
|
|
*/
|
|
boolean Adafruit_HTU21DF_Soft::begin(SoftwareWire *theWire)
|
|
{
|
|
_wire = theWire;
|
|
_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
|
|
}
|
|
|
|
/**
|
|
* Sends a 'reset' request to the HTU21DF, followed by a 15ms delay.
|
|
*/
|
|
void Adafruit_HTU21DF_Soft::reset(void)
|
|
{
|
|
_wire->beginTransmission(HTU21DF_I2CADDR);
|
|
_wire->write(HTU21DF_RESET);
|
|
_wire->endTransmission();
|
|
delay(15);
|
|
}
|
|
|
|
/**
|
|
* Performs a single temperature conversion in degrees Celsius.
|
|
*
|
|
* @return a single-precision (32-bit) float value indicating the measured
|
|
* temperature in degrees Celsius.
|
|
*/
|
|
float Adafruit_HTU21DF_Soft::readTemperature(void)
|
|
{
|
|
// OK lets ready!
|
|
_wire->beginTransmission(HTU21DF_I2CADDR);
|
|
_wire->write(HTU21DF_READTEMP);
|
|
_wire->endTransmission();
|
|
|
|
delay(50); // add delay between request and actual read!
|
|
|
|
uint8_t count = _wire->requestFrom(HTU21DF_I2CADDR, 3);
|
|
|
|
/* Make sure we got 3 bytes back. */
|
|
if (count != 3) {
|
|
return 0.0f;
|
|
}
|
|
|
|
/* Read 16 bits of data, dropping the last two status bits. */
|
|
uint16_t t = _wire->read();
|
|
t <<= 8;
|
|
t |= _wire->read() & 0b11111100;
|
|
|
|
uint8_t crc = _wire->read();
|
|
(void)crc;
|
|
|
|
float temp = t;
|
|
temp *= 175.72f;
|
|
temp /= 65536.0f;
|
|
temp -= 46.85f;
|
|
|
|
/* Track the value internally in case we need to access it later. */
|
|
_last_temp = temp;
|
|
|
|
return temp;
|
|
}
|
|
|
|
/**
|
|
* Performs a single relative humidity conversion.
|
|
*
|
|
* @return A single-precision (32-bit) float value indicating the relative
|
|
* humidity in percent (0..100.0%).
|
|
*/
|
|
float Adafruit_HTU21DF_Soft::readHumidity(void) {
|
|
/* Prepare the I2C request. */
|
|
_wire->beginTransmission(HTU21DF_I2CADDR);
|
|
_wire->write(HTU21DF_READHUM);
|
|
_wire->endTransmission();
|
|
|
|
/* Wait a bit for the conversion to complete. */
|
|
delay(50);
|
|
|
|
/* Read the conversion results. */
|
|
uint8_t count = _wire->requestFrom(HTU21DF_I2CADDR, 3);
|
|
|
|
/* Make sure we got 3 bytes back. */
|
|
if (count != 3) {
|
|
return 0.0f;
|
|
}
|
|
|
|
/* Read 16 bits of data, dropping the last two status bits. */
|
|
uint16_t h = _wire->read();
|
|
h <<= 8;
|
|
h |= _wire->read() & 0b11111100;
|
|
|
|
uint8_t crc = _wire->read();
|
|
(void)crc;
|
|
|
|
float hum = h;
|
|
hum *= 125.0f;
|
|
hum /= 65536.0f;
|
|
hum -= 6.0f;
|
|
|
|
/* Track the value internally in case we need to access it later. */
|
|
_last_humidity = hum;
|
|
|
|
return hum;
|
|
}
|