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121 lines
3.3 KiB
121 lines
3.3 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 <Arduino.h>
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#include "BaseAnalogSensor.h"
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extern "C" {
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#include "../libs/fs_math.h"
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}
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class MICS5525Sensor : public BaseAnalogSensor {
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public:
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// ---------------------------------------------------------------------
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// Public
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// ---------------------------------------------------------------------
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MICS5525Sensor() {
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_count = 2;
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_sensor_id = SENSOR_MICS5525_ID;
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}
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void calibrate() {
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setR0(_getResistance());
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}
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// ---------------------------------------------------------------------
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void setAnalogGPIO(unsigned char gpio) {
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_redGPIO = gpio;
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}
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unsigned char getAnalogGPIO() {
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return _redGPIO;
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}
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// ---------------------------------------------------------------------
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// Sensor API
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// ---------------------------------------------------------------------
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// Initialization method, must be idempotent
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void begin() {
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pinMode(_redGPIO, INPUT);
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_ready = true;
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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() {
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_Rs = _getResistance();
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}
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// Descriptive name of the sensor
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String description() {
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return String("MICS-5525 @ TOUT");
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}
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// Descriptive name of the slot # index
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String slot(unsigned char index) {
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return description();
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};
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// Address of the sensor (it could be the GPIO or I2C address)
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String address(unsigned char index) {
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return String("0");
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}
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// Type for slot # index
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unsigned char type(unsigned char index) {
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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) {
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if (0 == index) return _Rs;
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if (1 == index) return _getPPM();
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return 0;
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}
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private:
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unsigned long _getReading() {
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return analogRead(_redGPIO);
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}
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double _getResistance() {
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// get voltage (1 == reference) from analog pin
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double voltage = (float) _getReading() / 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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double _getPPM() {
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// According to the datasheet (https://airqualityegg.wikispaces.com/file/view/mics-5525-CO.pdf)
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return 764.2976 * fs_pow(2.71828, -7.6389 * ((float) _Rs / _R0));
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}
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unsigned char _redGPIO = MICS5525_RED_PIN;
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};
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#endif // SENSOR_SUPPORT && MICS5525_SUPPORT
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