Optimize your living or working space with Si7021-A20 and STM32F091RC
Precision weather tracking for your indoor world
Published Feb 26, 2024
Click board™
Temp&Hum 7 Click
Dev. board
Nucleo-64 with STM32F091RC MCU
Compiler
NECTO Studio
MCU
STM32F091RC
Our precise climate insights can be applied in homes, offices, factories, and more, providing valuable information for comfort and efficiency.
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Hardware Overview
How does it work?
Temp&Hum 7 Click is based on the Si7021-A20, a humidity and temperature digital sensor, which uses the I2C interface, from Silicon Labs. This sensor is produced using the patented low-K polymeric dielectrics for the humidity sensing, which allows it to achieve an excellent long-term stability. The Si7021-A20 offers an onboard digital signal processing. By applying the polynomial non-linearity correction, the measurements are linear across the range between 0% and 80% RH, retaining the accuracy of ±3% RH. The sensor can still be used in the range between 0% and 100% RH, in applications with slightly higher tolerances. Each sensor contains the factory calibration data in the internal non-volatile memory, so there is no need for additional calibration steps. The datasheet of the Si7021-A20 offers conversion formulas, which should be used to convert the readings from the sensor to physical values, expressed in %RH and °C. Due to the used capacitive
technology the sensor might exhibit a hysteresis effect. Exposed to the higher RH percentage, the sensor will develop an upward drift in respect to the factory calibration values. Similarly, if exposed to a low RH percentage, the sensor will develop a downward drift in respect to the factory calibration values. However, changing the RH conditions will affect the measurement drift, causing the hysteresis effect. The hysteresis is a common parameter of any sensor that uses the capacitive humidity sensing element. However, the Si7021-A20 incorporates very low hysteresis (±1% RH) due to the used low-K polymer technology. Besides the capacitive sensing elements, the sensor IC incorporates an analog front end (AFE), which consists of A/D converter, non-volatile memory, and the control logic section. The integrated A/D converter can be programmatically selected from the lowest 8/11-bit resolution, up to resolutions of 12/14 bits (RH/T). The
resolution selection affects the power consumption, as well as the data output rate. The response time of the RH readings might vary between 2.6ms for 8-bit resolution, up to 12ms for 12-bit resolution. The SHT21 sensor also features an integrated resistive heating element, used to evaporate condensation. The heating element can be programmed by using four control bits in the heater control register, allowing to control the heating amount, as well as the typical current draw of the internal heating element. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this Click board™ comes equipped with a library containing easy-to-use 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.
Software Support
Library Description
This library contains API for Temp&Hum 7 Click driver.
Key functions:
temphum7_get_relative_humidity- Relative humidity.temphum7_get_temperature- Get temerature.temphum7_get_firmware_revision- Firmware revision.
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 TempHum7 Click example
*
* # Description
* This application measurement temperature and humidity data.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes device and logger module and sets default configuration for measurements.
*
* ## Application Task
* Calculates and Logs temperature and relative humidity
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "temphum7.h"
// ------------------------------------------------------------------ VARIABLES
static temphum7_t temphum7;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
temphum7_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.
temphum7_cfg_setup( &cfg );
TEMPHUM7_MAP_MIKROBUS( cfg, MIKROBUS_1 );
temphum7_init( &temphum7, &cfg );
temphum7_default_cfg( &temphum7 );
}
void application_task ( void )
{
float temperature;
float relative_humidity;
temperature = temphum7_get_temperature( &temphum7, TEMPHUM7_HOLD_MASTER_MODE );
log_printf( &logger, "-> Temperature: %f C\r\n", temperature );
relative_humidity = temphum7_get_relative_humidity( &temphum7, TEMPHUM7_HOLD_MASTER_MODE );
log_printf( &logger, "-> Relative humidity: %f %%RH\r\n ", relative_humidity );
Delay_ms ( 1000 );
}
int main ( void )
{
/* Do not remove this line or clock might not be set correctly. */
#ifdef PREINIT_SUPPORTED
preinit();
#endif
application_init( );
for ( ; ; )
{
application_task( );
}
return 0;
}
// ------------------------------------------------------------------------ END
Additional Support
Resources
Category:Temperature & humidity
