File content as of revision 2:2186c624272f:

#include "HTU21D.h"
 




#if defined(__TT_M4G9__) | defined(__TT_M3HQ__)
#define DEFAULT_SDA_PIN  I2C_SDA
#define DEFAULT_SCL_PIN  I2C_SCL
#endif



HTU21D::HTU21D()
{
    i2c_ = new I2C(DEFAULT_SDA_PIN, DEFAULT_SCL_PIN);
    i2c_->frequency(400000);
}


HTU21D::HTU21D(PinName sda, PinName scl) {
 
    i2c_ = new I2C(sda, scl);
    //400KHz, as specified by the datasheet.
    i2c_->frequency(400000);
 
 
 
}
 
int HTU21D::sample_ctemp(void) {
 
    char tx[1];
    char rx[2];
    int status ;
    tx[0] = TRIGGER_TEMP_MEASURE; // Triggers a temperature measure by feeding correct opcode.
    i2c_->write((HTU21D_I2C_ADDRESS << 1) & 0xFE, tx, 1);
    wait_ms(50); // Per datasheet, wait long enough for device to sample temperature
    
    // Reads triggered measure
    i2c_->read((HTU21D_I2C_ADDRESS << 1) | 0x01, rx, 2);
    wait_ms(1);

    // Algorithm from datasheet to compute temperature.
    unsigned int rawTemperature = ((unsigned int) rx[0] << 8) | (unsigned int) rx[1];
    rawTemperature &= 0xFFFC;
 
    float tempTemperature = rawTemperature / (float)65536; //2^16 = 65536
    float realTemperature = -46.85 + (175.72 * tempTemperature); //From page 14
 
    return (int)realTemperature;
 
}
 
int HTU21D::sample_ftemp(void){
    int temptemp = sample_ctemp();
    int ftemp = temptemp * 1.8 + 32;
    
    return ftemp;
}
 
int HTU21D::sample_ktemp(void){
    int temptemp = sample_ctemp();
    int ktemp = temptemp + 274;
    
    return ktemp;
    
    
}
 
int HTU21D::sample_humid(void) {
 
    char tx[1];
    char rx[2];
 
 
    tx[0] = TRIGGER_HUMD_MEASURE; // Triggers a humidity measure by feeding correct opcode.
    i2c_->write((HTU21D_I2C_ADDRESS << 1) & 0xFE, tx, 1);
    wait_ms(16); // Per datasheet, wait long enough for device to sample humidity
    
    // Reads triggered measure
    i2c_->read((HTU21D_I2C_ADDRESS << 1) | 0x01, rx, 2);
    wait_ms(1);
    
    //Algorithm from datasheet.
    unsigned int rawHumidity = ((unsigned int) rx[0] << 8) | (unsigned int) rx[1];
 
    rawHumidity &= 0xFFFC; //Zero out the status bits but keep them in place
    
    //Given the raw humidity data, calculate the actual relative humidity
    float tempRH = rawHumidity / (float)65536; //2^16 = 65536
    float rh = -6 + (125 * tempRH); //From page 14
 
 
    return (int)rh;
 
}