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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.
*/
#pragma once
#include <iostream>
#include <string>
#include <mraa/aio.hpp>
#include <mraa/gpio.hpp>
namespace upm {
/**
* @brief DFRobot CO2 Sensor
* @defgroup mg811 libupm-mg811
* @ingroup dfrobot analog gas
*/
/**
* @library mg811
* @sensor mg811
* @comname DFRobot CO2 Sensor
* @altname MG811
* @type gas
* @man dfrobot
* @web http://www.dfrobot.com/index.php?route=product/product&product_id=1023
* @con analog
*
* @brief API for the DFRobot CO2 Sensor
*
* This sensor returns an an analog voltage that falls as the
* concentration of CO2 increases. It contains a heater that must
* be allowed to 'warm' up the sensor before measurements are stable
* (hours to days is the recommendation). It requires that the MCU
* be powered from an external power supply (not USB) at 5v, since
* the heater will consume significant current.
*
* The sensor should be allowed to 'heat' up for some time before
* beginning use, typically a couple of hours minimum. It also
* needs fairly precise calibration at 400ppm and 1000ppm to return
* meaningful results.
*
* The sensor also incorporates a potentiometer that can be adjusted
* to specific threshold. Once that threshold is reached, an LED
* on the sensor will light, and the digital pin will be driven
* high.
*
* @image html mg811.jpg
* @snippet mg811.cxx Interesting
*/
class MG811 {
public:
/**
* MG811 constructor
*
* @param pin Analog pin to use
* @param dpin Digital pin that indicates threshold
* @param aref Analog reference voltage; default is 5.0 V
*/
MG811(int pin, int dpin, float aref=5.0);
/**
* MG811 destructor
*/
~MG811();
/**
* Return a cumputed reference voltage to be used in calibration.
* @return Computed reference voltage
*/
float getReferenceVoltage();
/**
* Set calibration parameters. You should measure the reference
* voltage you get when at CO2 concentrations of 400ppm (ambient)
* and 1000ppm using the getReferenceVoltage() method. Then
* specify those voltages here for more accurate results.
*
* @param ppm400 The measured reference voltage at 400 ppm
* @param ppm40000 The measured reference voltage at 1000 ppm
*/
void setCalibration(float ppm400, float ppm1000);
/**
* Returns the voltage detected on the analog pin
*
* @return The detected voltage
*/
float volts();
/**
* Returns the computed CO2 concentration in ppm (Parts Per
* Million). This method will return 0.0 if the reference voltage
* is greater than the ppm400 value. Essentially, ppm values
* below 400 will be reported as 0.
*
* @return The computed CO2 concentration in ppm
*/
float ppm();
/**
* Read the digital pin and return true if the set threshold has
* been reached or exceeded. This threshold is set by adjusting
* the potentiometer on the sensor.
*
* @return true if the threshold has been reached, false otherwise
*/
bool thresholdReached();
protected:
mraa::Aio m_aio;
mraa::Gpio m_gpio;
// calibration values
float m_zeroPointValue;
float m_reactionValue;
// ADC resolution
int m_aRes;
private:
float m_aref;
};
}
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