Library Description

This library allows user to check CO2 (Carbon Dioxide) and tVOC (Total Volatile Organic Compounds) level of the air quality. The recalibration of the device is also allowed by this library. For more details, please, check full documentation.

Key functions:

• void airquality7_set_ppmco2( uint8_t *ppmco2_value ); - This function is used to send the ppmCO2 value given by an external analyzer to the Air quality 7 click in order to recalibrate its outputs.
• airquality7_err_t airquality7_get_status( uint16_t *tvoc_ppb, uint16_t *co2_ppm, uint32_t *res_val_ohm, uint8_t *err_byte ); - This function is used to read the Air quality 7 click status coded on tVOC data byte [0 - 1000 ppb], CO2 data byte [400 - 2000 ppm], resistor value data 3 bytes [Ohm], error status byte and CRC byte.
• airquality7_err_t airquality7_get_r0_calib( uint16_t *r0_kohm ); - This function is used to read the R0 (calibration) value in [kOhms] coded on 2 data bytes and CRC byte.

Examples description

The application is composed of three sections :

• System Initialization - Initializes all necessary peripherals and pins. Performs a delay time of a couple seconds because the Air quality 7 click needs some time to establish the measurements.
• Application Initialization - Initializes I2C driver and reads revision of the module. If CRC check is OK allows the program to go on, and if it's not OK, needs to restart the program.
• Application Task - Reads air quality status every 1500ms and shows the results on serial terminal.

void application_task( )
{
    airquality7_err_code = airquality7_get_status( &airquality7_tvoc_ppb, 
                                                   &airquality7_co2_ppm,
                                                   &airquality7_res_val_ohm, 
                                                   AIRQUALITY7_NULL );
                   
    if ( airquality7_err_code == AIRQUALITY7_ERR_OK )
    {
        char log_txt[ 50 ];
        uint8_t cnt;
        
        log_txt[ 0 ] = 13;
        log_txt[ 1 ] = 0;
        mikrobus_logWrite( log_txt, _LOG_TEXT );

        for ( cnt = 0; cnt < 70; cnt++ )
        {
            mikrobus_logWrite( " ", _LOG_TEXT );
            Delay_ms( 5 );
        }

        mikrobus_logWrite( log_txt, _LOG_TEXT );

        WordToStr( airquality7_tvoc_ppb, log_txt );
        Ltrim( log_txt );
        mikrobus_logWrite( " tVOC [ppb] = ", _LOG_TEXT );
        mikrobus_logWrite( log_txt, _LOG_TEXT );
        mikrobus_logWrite( ";  ", _LOG_TEXT );

        WordToStr( airquality7_co2_ppm, log_txt );
        Ltrim( log_txt );
        mikrobus_logWrite( "CO2 [ppm] = ", _LOG_TEXT );
        mikrobus_logWrite( log_txt, _LOG_TEXT );
        mikrobus_logWrite( ";  ", _LOG_TEXT );

        LongWordToStr( airquality7_res_val_ohm, log_txt );
        Ltrim( log_txt );
        mikrobus_logWrite( "Resistor value [ohm] = ", _LOG_TEXT );
        mikrobus_logWrite( log_txt, _LOG_TEXT );
    }
    
    Delay_ms( 1500 );
}

Other mikroE Libraries used in the example:

• Conversions
• C_String
• I2C
• UART

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.