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/*
* Author: Jon Trulson <jtrulson@ics.com>
* Copyright (c) 2015 Intel Corporation.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <iostream>
#include <string>
#include <stdexcept>
#include "otp538u.h"
#include "thermopile_vt_table.h"
#include "thermister_rt_table.h"
using namespace upm;
using namespace std;
OTP538U::OTP538U(int pinA, int pinO, float aref)
{
// this is the internal voltage reference on the Grove IR temp
// sensor module
m_vref = 2.5;
// analog reference in use
m_aref = aref;
// This is the value of the output resistor of the Grove IR
// temp sensor's SIG2 output (ambient)
m_vResistance = 2000000; // 2M ohms
// This was the default offset voltage in the seeedstudio code. You
// can adjust as neccessary depending on your calibration.
m_offsetVoltage = 0.014;
// We need around 1mV resolution, so use 12 bit resolution (4096)
// with a default aref of 5.0.
m_adcResolution = 4096;
if ( !(m_aioA = mraa_aio_init(pinA)) )
{
throw std::invalid_argument(std::string(__FUNCTION__) +
": mraa_gpio_init(pinA) failed, invalid pin?");
return;
}
// enable 12 bit resolution
mraa_aio_set_bit(m_aioA, 12);
if ( !(m_aioO = mraa_aio_init(pinO)) )
{
throw std::invalid_argument(std::string(__FUNCTION__) +
": mraa_gpio_init(pinO) failed, invalid pin?");
return;
}
// enable 12 bit resolution
mraa_aio_set_bit(m_aioO, 12);
}
OTP538U::~OTP538U()
{
mraa_aio_close(m_aioA);
mraa_aio_close(m_aioO);
}
float OTP538U::ambientTemperature()
{
const int samples = 5;
int val = 0;
float temp = 0;
float res;
for (int i=0; i<samples; i++)
{
val = mraa_aio_read(m_aioA);
temp += val;
usleep(10000);
}
temp = temp / samples;
temp = temp * m_aref / m_adcResolution;
// compute the resistance of the thermistor
res = m_vResistance * temp / (m_vref - temp);
// look it up in the thermistor (RT) resistence/temperature table
int rawslot;
int j;
for (j=0; j<otp538u_rt_table_max; j++)
if (otp538u_rt_table[j] < res)
{
rawslot = j;
break;
}
if (j >= otp538u_rt_table_max)
{
throw std::out_of_range(std::string(__FUNCTION__) +
": ambient temperature out of range.");
return 0;
}
// we need to compensate for the fact that we are supporting
// temperature values less than 0 (-20C), so adjust correspondingly
// so that we obtain the correct temperature 'slot'. This will be
// our base temperature.
int slot = rawslot - 20;
// too cold
if (slot < 0)
{
throw std::out_of_range(std::string(__FUNCTION__) +
": ambient temperature out of range.");
return 0;
}
// now compute the ambient temperature
float ambientTemp = slot - 1 +
(otp538u_rt_table[rawslot - 1]-res) / (otp538u_rt_table[rawslot - 1] -
otp538u_rt_table[rawslot]);
return ambientTemp;
}
float OTP538U::objectTemperature()
{
const int samples = 5;
const float reference_vol= 0.5; // what is this value? (from seeedstudio)
const float tempIncrement=10;
int val = 0;
float temp = 0;
float ambTemp = ambientTemperature();
for (int i=0; i<samples; i++)
{
val = mraa_aio_read(m_aioO);
temp += val;
usleep(10000);
}
temp = temp / samples;
float temp1 = temp * m_aref / m_adcResolution;
float sensorVolts = temp1 - (reference_vol + m_offsetVoltage);
// cout << "Sensor Voltage: " << sensorVolts << endl;
// search the VT (voltage/temperature) table to find the object
// temperature.
int slot;
// add +2 to compensate for the -20C and -10C slots below zero
int voltOffset = int(ambTemp / 10) + 1 + 2;
float voltage = sensorVolts * 10.0;
for (slot=0; slot<(otp538u_vt_table_max - 1); slot++)
{
if ( (voltage > otp538u_vt_table[slot][voltOffset]) &&
(voltage < otp538u_vt_table[slot+1][voltOffset]) )
{
break;
}
}
if (slot >= (otp538u_vt_table_max - 1))
{
throw std::out_of_range(std::string(__FUNCTION__) +
": object temperature out of range.");
return 0;
}
float objTemp = (float(tempIncrement) * voltage) /
( otp538u_vt_table[slot + 1][voltOffset] -
otp538u_vt_table[slot][voltOffset] );
// cout << "TABLE VALUE [" << slot << "][" <<
// voltOffset << "] = " << otp538u_vt_table[slot][voltOffset] << endl;
return (ambTemp + objTemp);
}
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