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84 lines
2.4 KiB
84 lines
2.4 KiB
// -----------------------------------------------------------------------------
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// MICS-5525 (and MICS-4514) CO Analog Sensor
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// Copyright (C) 2019 by Xose Pérez <xose dot perez at gmail dot com>
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// -----------------------------------------------------------------------------
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#if SENSOR_SUPPORT && MICS5525_SUPPORT
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#pragma once
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#include "BaseAnalogSensor.h"
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#include "../libs/fs_math.h"
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class MICS5525Sensor : public AnalogSensor {
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public:
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// ---------------------------------------------------------------------
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// Sensor API
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// ---------------------------------------------------------------------
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unsigned char id() const override {
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return SENSOR_MICS5525_ID;
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}
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unsigned char count() const override {
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return 2;
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}
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void calibrate() override {
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setR0(_getResistance());
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}
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// Pre-read hook (usually to populate registers with up-to-date data)
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void pre() override {
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_Rs = _getResistance();
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_ppm = _getPPM();
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}
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// Descriptive name of the sensor
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String description() const override {
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return F("MICS-5525 @ TOUT");
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}
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// Type for slot # index
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unsigned char type(unsigned char index) const override {
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if (0 == index) return MAGNITUDE_RESISTANCE;
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if (1 == index) return MAGNITUDE_CO;
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return MAGNITUDE_NONE;
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}
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// Current value for slot # index
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double value(unsigned char index) override {
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if (0 == index) return _Rs;
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if (1 == index) return _ppm;
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return 0;
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}
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private:
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double _getResistance() const {
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// get voltage (1 == reference) from analog pin
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double voltage = AnalogSensor::analogRead() / 1024.0;
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// schematic: 3v3 - Rs - P - Rl - GND
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// V(P) = 3v3 * Rl / (Rs + Rl)
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// Rs = 3v3 * Rl / V(P) - Rl = Rl * ( 3v3 / V(P) - 1)
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// 3V3 voltage is cancelled
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double resistance = (voltage > 0) ? _Rl * ( 1 / voltage - 1 ) : 0;
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return resistance;
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}
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// Calculate according to the datasheet (https://airqualityegg.wikispaces.com/file/view/mics-5525-CO.pdf)
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double _getPPM() const {
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return 764.2976 * fs_pow(2.71828, -7.6389 * ((float) _Rs / _R0));
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}
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double _ppm { 0.0 };
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};
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#endif // SENSOR_SUPPORT && MICS5525_SUPPORT
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