File content as of revision 1:6a589f1dd263:

/* mbed Linear Temperature Sensor library
 * Supports Microchip MCP9700/9701, National Semiconductor LM35
 *
 * Written by Todotani, Nov 22 2010
 */

#include "LinearTempSensor.h"

LinearTempSensor::LinearTempSensor(PinName ain, int N, SensorType type):
        // Initialize private variables using Initialization Lists
        // _ain(ain) is equivalent to _ain = new AnalogIn(ain)
        // _sample(N) is equivalent to _sample = N
        _ain(ain), _samples(N), _type(type) {
    sampleBuffer = (float *)malloc(sizeof(float) * _samples);
    sampleCount = 0;
    index       = 0;
    Vref        = 3300;
    bufferNotFilled = true;

    // Set constants to calculate temperature from sensor value
    switch (_type) {
        case LM35:
            V0 = 0.0f;
            Tc = 10.0f;
            break;
      case MCP9701:
            V0 = 400.0f;
            Tc = 19.5f;
            break;
      case MCP9700:
       default:
            V0 = 500.0f;
            Tc = 10.0f;
    }
    
    for (int i = 0; i < _samples; i++)
        sampleBuffer[i] = 0.0f;
}


LinearTempSensor::~LinearTempSensor() {
    free(sampleBuffer);
}


float LinearTempSensor::Sense() {
    float val;

    val = _ain * Vref;
    sampleBuffer[index] = val;
    //printf("Index:%d  ", index);    // Debug print
    if ( ++index >= _samples )
        index = 0;

    if ( bufferNotFilled && (sampleCount == _samples) ) {
        bufferNotFilled = false;
    }
    //printf("flag:%d  ", bufferNotFilled);   // Debug print
    sampleCount++;

    return val;
}


float LinearTempSensor::GetAverageTemp() {
    float sum = 0;
    int i, numberOfsumples;

    if (sampleCount == 0)
        return 0;

    if (bufferNotFilled) {
        // In case number of samples less than buffer lenght
        for (i = 0; i < sampleCount; i++) {
            sum += sampleBuffer[i];
        }
        numberOfsumples = sampleCount;
    } else {
        // In case buffer is filled
        for (i = 0; i < _samples; i++) {
            sum += sampleBuffer[i];
        }
        numberOfsumples = _samples;
    }

    return ((sum / numberOfsumples) - V0) / Tc;    //  Temp = (Vout - V0) / Tc
}


float LinearTempSensor::GetLatestTemp() {
    return (sampleBuffer[(sampleCount-1)%_samples] - V0) / Tc;
}