MHZ16 Class Reference

API support for the Grove CO2 sensor. More...

Detailed Description

• ID: mhz16
• Name: CO2 Sensor
• Other Names: MHZ16 Serial CO2 Sensor
• Category: gaseous
• Manufacturer: seeed
• Connection: uart
• Link: http://wiki.seeed.cc/Grove-CO2_Sensor/

This class implements support for the Grove CO2 sensor.

Its CO2 detection range is 0-2,000 ppm. It requires a 2-3 minute warm-up time before reporting valid data.

    // Instantiate a MHZ16 serial CO2 sensor on uart 0.
    // This example was tested on the Grove CO2 sensor module.

    upm::MHZ16 co2(0);

    // make sure port is initialized properly.  9600 baud is the default.
    if (!co2.setupTty(B9600)) {
        cerr << "Failed to setup tty port parameters" << endl;
        return 1;
    }

    cout << "Make sure that the sensor has had at least 3 minutes to warm up" << endl;
    cout << "or you will not get valid results." << endl;
    cout << "The temperature reported is not the ambient temperature, " << endl;
    cout << "but rather the temperature of the sensor elements." << endl;

    upm_delay(1);

    while (shouldRun) {
        if (!co2.getData()) {
            cerr << "Failed to retrieve data" << endl;
            continue;
        }

        cout << "CO2 concentration: " << co2.getGas() << " PPM, "
             << "Temperature (in C): " << co2.getTemperature() << endl;

        upm_delay(2);
    }

Public Member Functions
	MHZ16 (int uart)
	MHZ16 (const std::string &uart_raw="/dev/ttyS0")
virtual	~MHZ16 ()
bool	dataAvailable (unsigned int millis)
int	readData (char *buffer, int len)
int	writeData (char *buffer, int len)
bool	setupTty (speed_t baud=B9600)
bool	verifyPacket (uint8_t *pkt, int len)
bool	getData ()
int	getGas ()
int	getTemperature ()
void	calibrateZeroPoint ()

Protected Member Functions
int	ttyFd ()

Constructor & Destructor Documentation

MHZ16

(

int

uart

)

MHZ16 constructor

Parameters

uart	Default mraa UART index to use

MHZ16

(

const std::string &

uart_raw = "/dev/ttyS0"

)

MHZ16 constructor

Parameters

uart_raw

Full path to UART device.

~MHZ16 ( )

virtual

MHZ16 destructor

Member Function Documentation

bool dataAvailable

(

unsigned int

millis

)

Checks to see if there is data available for reading

Parameters

millis

Number of milliseconds to wait; 0 means no waiting.

Returns

True if there is data available for reading

int readData	(	char *	buffer,
		int	len
	)

Reads any available data in a user-supplied buffer. Note: the call blocks until data is available to be read. Use dataAvailable() to determine whether there is data available beforehand, to avoid blocking.

Parameters

buffer	Buffer to hold the data read
len	Length of the buffer

Returns

Number of bytes read

int writeData	(	char *	buffer,
		int	len
	)

Writes the data in the buffer to the device

Parameters

buffer	Buffer to hold the data read
len	Length of the buffer

Returns

Number of bytes written

bool setupTty

(

speed_t

baud = B9600

)

Sets up proper tty I/O modes and the baud rate. The default baud rate is 9,600 (B9600).

Parameters

baud	Desired baud rate.

Returns

True if successful

bool verifyPacket	(	uint8_t *	pkt,
		int	len
	)

Verifies the packet header and indicates its validity

Parameters

pkt	Packet to check

Returns

True if the checksum is valid, false otherwise

bool getData

(

)

Queries the sensor and gets the gas (CO2) concentration and temperature data. Should be called before other "get" functions.

Returns

True if successful

int getGas

(

)

Returns the gas (CO2) concentration data.

Returns

Gas concentration

int getTemperature

(

void

)

Returns the temperature data.

Returns

Temperature in Celsius

void calibrateZeroPoint

(

)

Sets the zero point of the sensor

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The documentation for this class was generated from the following files:

• src/mhz16/mhz16.hpp
• src/mhz16/mhz16.cxx