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HTU21D Click

HTU21D Click carries a high-precision, easy-to-use relative humidity sensor with temperature output.

Click Product page

Click library

  • Author : MikroE Team
  • Date : Jan 2020.
  • Type : I2C type

Software Support

We provide a library for the Htu21d Click as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Package can be downloaded/installed directly form compilers IDE(recommended way), or downloaded from our LibStock, or found on mikroE github account.

Library Description

This is explanation for Htu21d Click driver.

Standard key functions :

  • Config Object Initialization function.

void htu21d_cfg_setup ( htu21d_cfg_t *cfg );

  • Initialization function.

HTU21D_RETVAL htu21d_init ( htu21d_t *ctx, htu21d_cfg_t *cfg );

  • Click Default Configuration function.

void htu21d_default_cfg ( htu21d_t *ctx );

Example key functions :

  • This function initializes Click configuration structure to init state.

void htu21d_cfg_setup ( htu21d_cfg_t *cfg );

  • This function initializes all necessary pins and peripherals used for this Click.

HTU21D_RETVAL htu21d_init ( htu21d_t *ctx, htu21d_cfg_t *cfg );

  • This function writes data to the desired register.

void htu21d_generic_write ( htu21d_t *ctx, uint8_t reg, uint8_t *data_buf, uint8_t len );

  • This function reads data from the desired register.

void htu21d_generic_read ( htu21d_t *ctx, uint8_t reg, uint8_t *data_buf, uint8_t len );

  • Function read 24-bit data from register address of HTU21D.

uint32_t htu21d_read_data ( htu21d_t *ctx, uint8_t reg_adr );

  • Function sends command to HTU21D.

void htu21d_send_cmd ( htu21d_t *ctx, uint8_t cmd_byte );

  • This function reads data from the desired register.

void htu21d_readdata ( htu21d_t *ctx, uint8_t reg, uint8_t *data_buf, uint8_t len );

  • Function read and calculate temperature in degrees Celsius from the HTU21D sensor.

float htu21d_get_temperature ( htu21d_t *ctx );

  • Function read and calculate humidity percentage from the HTU21D sensor.

float htu21d_get_humidity ( htu21d_t *ctx );

Examples Description

The application is composed of two sections.

The demo application is composed of two sections :

Application Init

Initialization driver enable's - I2C, soft reset switch OFF and ON the HTU21D sensor,hold ( required ) after reset 100 [ ms ] and start write log.

void application_init ( void ) { log_cfg_t log_cfg; htu21d_cfg_t cfg;

/** 
 * Logger initialization.
 * Default baud rate: 115200
 * Default log level: LOG_LEVEL_DEBUG
 * @note If USB_UART_RX and USB_UART_TX 
 * are defined as HAL_PIN_NC, you will 
 * need to define them manually for log to work. 
 * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
 */
LOG_MAP_USB_UART( log_cfg );
log_init( &logger, &log_cfg );
log_printf( &logger, "---- Application Init ----\r\n" );

//  Click initialization.

htu21d_cfg_setup( &cfg );
HTU21D_MAP_MIKROBUS( cfg, MIKROBUS_1 );
htu21d_init( &htu21d, &cfg );

htu21d_send_cmd ( &htu21d, HTU21D_SOFT_RESET );
Delay_ms ( 15 );

log_printf( &logger, "---------------------------\r\n" );
log_printf( &logger, "         HTU21D       \r\n" );
log_printf( &logger, "---------------------------\r\n" );

}

Application Task

This is a example which demonstrates the use of HTU21D Click board.Measured temperature and humidity data from the HDC1000 sensor.Convert temperature data to degrees Celsius and humidity data to percentarg. Results are being sent to the Usart Terminal where you can track their changes. All data logs on usb uart for aproximetly every 3 sec.

void application_task ( void ) { // Task implementation. temperature = htu21d_get_temperature( &htu21d ); log_printf( &logger, " Temperature : %.2f C \r\n", temperature );

humidity = htu21d_get_humidity( &htu21d );
log_printf( &logger, " Humidity : %.2f % \r\n", humidity );

log_printf( &logger, "---------------------------\r\n" );

Delay_ms ( 1000 );
Delay_ms ( 1000 );
Delay_ms ( 1000 );

}

The full application code, and ready to use projects can be installed directly form compilers IDE(recommneded) or found on LibStock page or mikroE GitHub accaunt.

Other mikroE Libraries used in the example:

  • MikroSDK.Board
  • MikroSDK.Log
  • Click.Htu21d

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.