Track the climate with ease using HTU21D and STM32F091RC
From scorching heat to refreshing breezes
Published Feb 26, 2024
Click board™
HTU21D Click
Dev. board
Nucleo-64 with STM32F091RC MCU
Compiler
NECTO Studio
MCU
STM32F091RC
Ensure optimal conditions for enhanced productivity and well-being in any indoor environment
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Hardware Overview
How does it work?
HTU21D Click is based on the HTU21D, an easy-to-use, highly accurate digital humidity sensor with temperature output from TE Connectivity. The HTU21D can read humidity over the full range of 0 to 100% RH with a typical accuracy of ±2% over the range of 5% to 95% RH, while its maximum temperature range is from -40 to 125°C. It has a typical accuracy of ±0.3°C over 0 to 70°C. The HTU21D makes a perfect choice for environmental sensing and data logging for weather stations or humidity control systems. It should be noted that
this sensor isn’t recommended for harsh environments where it could come in contact with water (such as rain). The HTU21D has a resolution of 0.7% RH and 0.040°C with conversion times of 2ms and 11ms, respectively. For more demanding requirements, the HTU21D allows users to increase the resolution at the expense of increased conversion time. For example, in full resolution mode, the HTU21D can provide 0.04% RH with a conversion time of 14ms and 0.01°C with a conversion time of 44ms. The HTU21D
communicates with MCU using the standard I2C 2-Wire interface with a maximum frequency of 400kHz and a fixed I2C address set to 0x40. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.
Features overview
Development board
Nucleo-64 with STM32F091RC MCU offers a cost-effective and adaptable platform for developers to explore new ideas and prototype their designs. This board harnesses the versatility of the STM32 microcontroller, enabling users to select the optimal balance of performance and power consumption for their projects. It accommodates the STM32 microcontroller in the LQFP64 package and includes essential components such as a user LED, which doubles as an ARDUINO® signal, alongside user and reset push-buttons, and a 32.768kHz crystal oscillator for precise timing operations. Designed with expansion and flexibility in mind, the Nucleo-64 board features an ARDUINO® Uno V3 expansion connector and ST morpho extension pin
headers, granting complete access to the STM32's I/Os for comprehensive project integration. Power supply options are adaptable, supporting ST-LINK USB VBUS or external power sources, ensuring adaptability in various development environments. The board also has an on-board ST-LINK debugger/programmer with USB re-enumeration capability, simplifying the programming and debugging process. Moreover, the board is designed to simplify advanced development with its external SMPS for efficient Vcore logic supply, support for USB Device full speed or USB SNK/UFP full speed, and built-in cryptographic features, enhancing both the power efficiency and security of projects. Additional connectivity is
provided through dedicated connectors for external SMPS experimentation, a USB connector for the ST-LINK, and a MIPI® debug connector, expanding the possibilities for hardware interfacing and experimentation. Developers will find extensive support through comprehensive free software libraries and examples, courtesy of the STM32Cube MCU Package. This, combined with compatibility with a wide array of Integrated Development Environments (IDEs), including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE, ensures a smooth and efficient development experience, allowing users to fully leverage the capabilities of the Nucleo-64 board in their projects.
Microcontroller Overview
MCU Card / MCU
Architecture
ARM Cortex-M0
MCU Memory (KB)
256
Silicon Vendor
STMicroelectronics
Pin count
64
RAM (Bytes)
32768
You complete me!
Accessories
Click Shield for Nucleo-64 comes equipped with two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the STM32 Nucleo-64 board with no effort. This way, Mikroe allows its users to add any functionality from our ever-growing range of Click boards™, such as WiFi, GSM, GPS, Bluetooth, ZigBee, environmental sensors, LEDs, speech recognition, motor control, movement sensors, and many more. More than 1537 Click boards™, which can be stacked and integrated, are at your disposal. The STM32 Nucleo-64 boards are based on the microcontrollers in 64-pin packages, a 32-bit MCU with an ARM Cortex M4 processor operating at 84MHz, 512Kb Flash, and 96KB SRAM, divided into two regions where the top section represents the ST-Link/V2 debugger and programmer while the bottom section of the board is an actual development board. These boards are controlled and powered conveniently through a USB connection to program and efficiently debug the Nucleo-64 board out of the box, with an additional USB cable connected to the USB mini port on the board. Most of the STM32 microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the STM32 Nucleo-64 board with our Click Shield for Nucleo-64, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Click board™ Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Nucleo-64 with STM32F091RC MCU as your development board.
Track your results in real time
Application Output
1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.
2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.
3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.
Software Support
Library Description
This library contains API for HTU21D Click driver.
Key functions:
htu21d_cfg_setup- This function initializes click configuration structure to init statehtu21d_init- This function initializes all necessary pins and peripherals used for this clickhtu21d_generic_write- This function writes data to the desired registerhtu21d_generic_read- This function reads data from the desired registerhtu21d_read_data- Function read 24-bit data from register address of the HTU21Dosd_enable_video_buffer- This function enables video bufferosd_clear_display_memory- This function clears display memoryosd_insert_custom_char- This function writes custom characterosd_enable_video_buffer- This function enables video buffer
Open Source
Code example
The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.
/*!
* \file
* \brief Htu21d Click example
*
* # Description
* The 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.
*
* ## 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.
*
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "htu21d.h"
// ------------------------------------------------------------------ VARIABLES
static htu21d_t htu21d;
static log_t logger;
static float temperature;
static float humidity;
// ------------------------------------------------------- ADDITIONAL FUNCTIONS
// ------------------------------------------------------ APPLICATION FUNCTIONS
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_info( &logger, "---- Application Init ----" );
// 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( 500 );
log_printf( &logger, "-----------------------\r\n" );
log_printf( &logger, " HTU21D\r\n" );
log_printf( &logger, "-----------------------\r\n" );
}
void application_task ( void )
{
// Task implementation.
temperature = htu21d_get_temperature( &htu21d );
log_printf( &logger, " Temperature : %.2f degC\r\n", temperature );
humidity = htu21d_get_humidity( &htu21d );
log_printf( &logger, " Humidity : %.2f %%\r\n", humidity );
log_printf( &logger, "-----------------------\r\n" );
Delay_ms( 3000 );
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
