otp538u: Initial implementation

This module was tested on the Grove non-contact IR Temperature
Sensor.  The tables included are only valid for a distance of 9cm.

Signed-off-by: Jon Trulson <jtrulson@ics.com>
Signed-off-by: Zion Orent <zorent@ics.com>
Signed-off-by: John Van Drasek <john.r.van.drasek@intel.com>

src/otp538u/otp538u.cxx

@@ -0,0 +1,189 @@
+/*
+ * 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 "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)) )
+    {
+      cerr << __FUNCTION__ << ": mraa_aio_init() failed" << endl;
+      return;
+    }
+
+  // enable 12 bit resolution
+  mraa_aio_set_bit(m_aioA, 12);
+
+  if ( !(m_aioO = mraa_aio_init(pinO)) )
+    {
+      cerr << __FUNCTION__ << ": mraa_aio_init() failed" << endl;
+      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)
+    { 
+      cerr << __FUNCTION__ << ": ambient temperature out of range." << endl;
+      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)
+    {
+      cerr << __FUNCTION__ << ": ambient temperature out of range." << endl;
+      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; slot++)		
+    {
+      if ( (voltage > otp538u_vt_table[slot][voltOffset]) &&
+           (voltage < otp538u_vt_table[slot+1][voltOffset]) )
+        {
+          break;
+        }
+    }
+
+  if (slot >= (otp538u_vt_table_max - 1))
+    {
+      cerr << __FUNCTION__ << ": object temperature out of range." << endl;
+      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);
+}