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htu21d: fixed 16-bit i2c reads and added extra functionality

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Fixed 16-bit read code to use the correct mraa function to align with
the datasheet.  Added code for dew point calculation and single function
to retreive temp, humidity, and dewpoint.  Other clean up as well.

Signed-off-by: Bill Penner <william.penner@intel.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>
This commit is contained in:
Bill Penner
2016-08-25 07:37:04 -07:00
committed by Mihai Tudor Panu
parent 372d3e980f
commit 77fbf49f93
2 changed files with 93 additions and 13 deletions
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64
src/htu21d/htu21d.cpp
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@ -27,6 +27,7 @@
#include <unistd.h>
#include <stdlib.h>
#include <endian.h>
#include "htu21d.hpp"
@ -52,7 +53,7 @@ HTU21D::HTU21D(int bus, int devAddr) : m_i2ControlCtx(bus) {
void
HTU21D::resetSensor(void)
{
uint8_t data;
uint8_t data = HTU21D_SOFT_RESET;
m_i2ControlCtx.address (m_controlAddr);
m_i2ControlCtx.write (&data, 1);
usleep(20000);
@ -71,7 +72,7 @@ HTU21D::convertTemp(int32_t regval)
* Convert register value to %RH * 1000
*/
int32_t
HTU21D::convertRH(int regval)
HTU21D::convertRH(int32_t regval)
{
return ((15625 * (regval & 0xFFFC)) >> 13) - 6000;
}
@ -81,13 +82,13 @@ HTU21D::sampleData(void)
{
uint32_t itemp;
itemp = i2cReadReg_16(HTU21D_READ_TEMP_HOLD);
itemp = be16toh(i2cReadReg_16(HTU21D_READ_TEMP_HOLD));
m_temperature = convertTemp(itemp);
itemp = i2cReadReg_16(HTU21D_READ_HUMIDITY_HOLD);
itemp = be16toh(i2cReadReg_16(HTU21D_READ_HUMIDITY_HOLD));
m_humidity = convertRH(itemp);
return 0;
return itemp == 0xFFFF;
}
float
@ -139,6 +140,55 @@ HTU21D::setHeater(int bEnable)
return 0;
}
/*
* Use the equation from the datasheet to calculate the partial pressure
* and then calculate the dew point temperature in degree C. Typical
* use would be after reading the temp and humidity the partial
* pressure can be caculated using the previously read values.
*/
float
HTU21D::getDewPoint(int bSampleData)
{
if (bSampleData) {
sampleData();
}
float fA = 8.1332;
float fB = 1762.39;
float fC = 235.66;
float fT = getTemperature(false);
float fRH = getHumidity(false);
float fPP = exp10(fA - (fB / (fT + fC)));
float fDP = -(fB / (log10(fRH * fPP / 100) - fA) + fC);
return (fDP);
}
/*
* Function to optimize reading of values from the device.
* This function will always initiate a read from the sensor
* and return the values and dew point calculated value
*/
int
HTU21D::getHumidityData(float* pfHum, float* pfHumTemp, float* pfDewPt)
{
float fHum = getHumidity(true);
float fTemp = getTemperature(false);
float fDewPt = getDewPoint(false);
float fCHum = getCompRH(false);
if (pfHum)
*pfHum = fCHum;
if (pfHumTemp)
*pfHumTemp = fTemp;
if (pfDewPt)
*pfDewPt = fDewPt;
return 0;
}
/*
* Test function: when reading the HTU21D many times rapidly should
* result in a temperature increase. This test will verify that the
@ -223,9 +273,7 @@ uint16_t
HTU21D::i2cReadReg_16 (int reg) {
uint16_t data;
m_i2ControlCtx.address(m_controlAddr);
data = (uint16_t)m_i2ControlCtx.readReg(reg) << 8;
data |= (uint16_t)m_i2ControlCtx.readReg(reg+1);
return data;
return m_i2ControlCtx.readWordReg(reg);
}
uint8_t