RAK MQx sensor modules

This library is used with the RAk12004, RAK12008, RAK12009 and other gas sensor modules.
This library provides easy to use functions to setup the RAKwireless MQx sensor modules and read the gas concentration in ppm. These modules use the ADC121C021 analog to digital converter with a I2C interface.
The ADC121C021 is a low-power, monolithic, 12-bit, analog-to-digital converter. The device features an I2C compatible serial interface. The ADC121C021's Alert feature provides an interrupt that is activated when the analog input violates a programmable upper or lower limit value. This library provides basic support for the ADC121C021 ADC.

• WisBlock MQ2 Gas Sensor RAK12004
• WisBlock CO2 Gas Sensor RAK12008
• WisBlock Gas Sensor RAK12009

Documentation

• RAKwireless RAK12004 Gas sensor
• RAKwireless RAK12008 CO2 Gas sensor (coming soon)
• RAKwireless RAK12009 Gas sensor (coming soon)
• Library Repository - Product repository for the MQx Sensor Modules.

Installation

In Arduino IDE open Sketch->Include Library->Manage Libraries then search for RAK-MQx.

In PlatformIO open PlatformIO Home, switch to libraries and search for RAK-MQx. Or install the library project depend by adding

lib_deps =
  rakwireless/RAKwireless MQx library

into platformio.ini

For manual installation download the archive, unzip it and place the RAK-MQx-Library folder into the library directory.
In Arduino IDE this is usually /libraries/
In PlatformIO this is usually <user/.platformio/lib>

Usage

The library provides an ADC class, which allows to read gas concentrations from the RAKwireless MQx sensor modules. Check out the examples how to read gas concentrations from a MQ2 gas sensor with the RAK12004.

This class provides the following methods:

ADC121C021();
Constructor for ADC interface.

bool begin(uint8_t addr, TwoWire &theWire);
Init the ADC121C021 device.

Parameters:

Direction	Name	Function
in	addr	I2C address of the ADC121C021
in	&theWire	I2C interface to be used
return		If the initialization succeeds return true else return false

MQx functions

void setVoltageResolution(float value);
Set the resolution voltage

Parameters:

Direction	Name	Function
in	value	if use 5V supply for MQx sensor to set value 5.0 if use 3.3V supply for MQx sensor to set value 3.3

float getVoltageResolution();
Gets the resolution voltage configuration.

Parameters:

Direction	Name	Function
return		the value of the resolution voltage configuration

void setR0(float R0 = 10);
Set the resistance R0 of the sensor at a known concentration without the presence of other gases, or in fresh air.

Parameters:

Direction	Name	Function
in	R0	the resistance of the sensor at fresh air.

float getR0();
Gets the R0 parameter.

Parameters:

Direction	Name	Function
return		R0 in kOhm

void setRL(float RL = 10);
Set the resistance RL of the sensor at a known concentration without the presence of other gases, or in fresh air.

Parameters:

Direction	Name	Function
in	RL	the resistance of the sensor at fresh air.

float getRL();
Gets the RL parameter.

Parameters:

Direction	Name	Function
return		RL in kOhm

void setA(float K);
Set the slope of the line

Parameters:

Direction	Name	Function
in	K	the slope of the line configuration

float getA();
Get the slope of the line parameter

Parameters:

Direction	Name	Function
return		the slope of the line configuration

void setB(float b);
Set config Y intercept parameter

Parameters:

Direction	Name	Function
in	b	Y intercept

float getB();
Get the Y intercept parameter configuration

Parameters:

Direction	Name	Function
return		Y intercept parameter

User functions

float getSensorVoltage(); Gets the voltage of sensor output.

Parameters:

Direction	Name	Function
return		voltage V

float calibrateR0(float ratioInCleanAir);
Set the ratio of RS/R0 in clean air

Parameters:

Direction	Name	Function
in	ratioInCleanAir	ratioInCleanAir = RS/R0
return		R0 MQx sensor resistance in the clean air

void setRegressionMethod(uint8_t method);
Set the regression method

Parameters:

Direction	Name	Function
in	method	set the regression method if=1 use Exponential else Linear Exponential: PPM = A*(RS/R0)^B Linear: PPM = pow(10, (log10(RS/R0)-B)/A)

uint8_t getRegressionMethod();
Gets the regression method

Parameters:

Direction	Name	Function
return		the regression method

float readSensor();
Read the MQx sensor data to PPM

Parameters:

Direction	Name	Function
return		MQx sensor data PPM

Direct ADC functions

uint8_t readConfigRegister();
Read the Configuration Register data, the register address is 0x02.

Parameters:

Direction	Name	Function
return		Configuration Register data

uint8_t readAlertStatus();
Get the current status of the alert flag If the flag is set, the low or high alert indicators are set as appropriate.

Parameters:

Direction	Name	Function
return		alert status

uint8_t readAlertLowStatus();
Get the current status of the Lower Range Alert Flag. readAlertStatus() must be called to update this value.

Parameters:

Direction	Name	Function
return		Lower Range Alert Flag status

uint8_t readAlertHighStatus();
Get the current status of the Over Range Alert Flag. readAlertStatus() must be called to update this value.

Parameters:

Direction	Name	Function
return		Higher Range Alert Flag status

void clearAlertStatus();
Clears the alert low and alert high flags.

Parameters:

Direction	Name	Function

void configCycleTime(uint8_t cycletime);
Sets the Configuration Register of Cycle Time bits value,when the value set to zeros, the automatic conversion mode is disabled. This is the case at power-up.

Parameters:

Direction	Name	Function
in	cycletime	the conversion intervals of convert time can be 0-7 value Conversion Interval Typical fconvert (ksps) 0 Automatic Mode Disabled 0 1 Tconvert x 32 27 2 Tconvert x 64 13.5 3 Tconvert x 128 6.7 4 Tconvert x 256 3.4 5 Tconvert x 512 1.7 6 Tconvert x 1024 0.9 7 Tconvert x 2048 0.4

uint8_t readCycleTime();
Read the Configuration Register of Cycle Time bits value.

Parameters:

Direction	Name	Function
return		the Cycle Time bits value from the Configuration Register

void configAlertHold(configType alertHold);
Sets the Alert Hold bit enable or disable.

Parameters:

Direction	Name	Function
in	alertHold	Enable:enable alert hold, Disable:disable alert hold.

uint8_t readAlertHold();
Get the Alert Hold bit status from the Configuration Register

Parameters:

Direction	Name	Function
return		the value of the Alert Hold bit

void configAlertFlag(configType alertflag);
Config the Alert Flag Enable bit,This controls the alert status bit [D15] in the Conversion Result register.

Parameters:

Direction	Name	Function
in	alertflag	Enable or Disable.

uint8_t readAlertFlag();
Get the bit value of Alert Flag Enable Status from the Configuration Register

Parameters:

Direction	Name	Function
return		the bit value of Alert Flag Enable

void configAlertPin(configType alertpin);
Config the alert pin output enable or disable when ALERT come.

Parameters:

Direction	Name	Function
in	alertpin	Enable or Disable

uint8_t readAlertPin();
Get the Alert Pin Enable Status from the Configuration Register.

Parameters:

Direction	Name	Function
return		the Alert Pin Enable Status register value

void configPolarity(polarityType polarity);
Config the alert pin output level polarity when ALERT come.

Parameters:

Direction	Name	Function
in	polarity	High or Low

uint8_t readPolarity();
Get the alert pin output level polarity configuration.

Parameters:

Direction	Name	Function
return		the polarity configuration

void setAlertLowThreshold(uint16_t threshold);
Sets the lower limit threshold value.

Parameters:

Direction	Name	Function
in	threshold	threshold value

uint16_t readAlertLowThreshold();
Get the value of the lower limit threshold value configuration

Parameters:

Direction	Name	Function
return		the lower limit threshold value

void setAlertHighThreshold(uint16_t threshold);
Sets the upper limit threshold value.

Parameters:

Direction	Name	Function
in	threshold	the upper limit threshold value

uint16_t readAlertHighThreshold();
Get the value of the upper limit threshold value configuration

Parameters:

Direction	Name	Function
return		the upper limit threshold value

void setHysteresis(uint16_t hysteresis);
Config the hysteresis value

Parameters:

Direction	Name	Function
in	hysteresis	hysteresis value

uint16_t readHysteresis();
Get the hysteresis value configuration

Parameters:

Direction	Name	Function
return		the hysteresis value configuration

uint16_t readLowestConversion();
Gets the Lowest Conversion result recorded from the Lowest Conversion Register.

Parameters:

Direction	Name	Function
return		the lowest conversion result value

void clearLowestConversion();
Clears the Lowest Conversion register value.

uint16_t readHighestConversion();
Gets the Highest Conversion result recorded from the Highest Conversion Register.

Parameters:

Direction	Name	Function
return		the highest conversion result value

void clearHighestConversion();
Clears the Highest Conversion register value.

uint16_t getAdcValue();
Read the ADC conversation value from the Conversion Register.

Parameters:

Direction	Name	Function
return		ADC conversation result