Stay safe from harmful NO2 with MiCS-2714 and STM32F302VC
NO2 detect, health protect: Your solution for cleaner, safer air
Published Jul 22, 2025
Click board™
NO2 2 Click
Dev. board
CLICKER 4 for STM32F302VCT6
Compiler
NECTO Studio
MCU
STM32F302VC
Join the fight against NO2 pollution with your engineering skills.
A
A
Hardware Overview
How does it work?
NO2 2 Click is based on the MiCS-2714 sensor, a compact MOS sensor from SGX Sensortech. This sensor comprises a micromachined metal oxide semiconductor diaphragm with an integrated heating resistor. The resistor produces heat, which catalyzes the reaction, affecting the electrical resistance of the oxide layer itself. The temperature of the heater is quite high: it ranges from 350 °C to 550 °C. After the initial preheating period, the sensor can detect gas changes in intervals below two seconds. The resistance of the MiCS-2714 sensor does not change linearly with the gas concentration, so a proper calibration must be performed before using it for absolute gas concentration measurement applications. The impedance changes the most when used with low
gas concentrations. As the atmosphere gets saturated with gas, the impedance changes slowly. The MiCS-2714 sensor is a simple device: it has only four connections. Two pins are the connections of the internal heating element, while the other two are the MOS sensor connections. The application is reduced to calculating a proper resistor for the voltage divider. The middle tap between the sensor (as a resistor) and the fixed resistance provides an output voltage. It directly depends on the sensor's resistance, allowing it to be used as the input into the MCP3201, a low-power 12-bit A/D converter with an I2C interface, from Microchip. This ADC allows the output voltage to be translated into digital information, accessed over the I2C pins on the mikroBUS™
socket. By using the power supply voltage as the voltage reference for the conversion, this ADC further reduces the complexity of the design, still offering a good conversion quality, thanks to its low noise input. Due to the sensor's inert nature, this ADC is more than fast enough, although it can provide up to 22.3ksps when operated in the I2C Fast mode. This Click board™ can be operated only with a 5V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, it 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
Clicker 4 for STM32F3 is a compact development board designed as a complete solution, you can use it to quickly build your own gadgets with unique functionalities. Featuring a STM32F302VCT6, four mikroBUS™ sockets for Click boards™ connectivity, power managment, and more, it represents a perfect solution for the rapid development of many different types of applications. At its core, there is a STM32F302VCT6 MCU, a powerful microcontroller by STMicroelectronics, based on the high-
performance Arm® Cortex®-M4 32-bit processor core operating at up to 168 MHz frequency. It provides sufficient processing power for the most demanding tasks, allowing Clicker 4 to adapt to any specific application requirements. Besides two 1x20 pin headers, four improved mikroBUS™ sockets represent the most distinctive connectivity feature, allowing access to a huge base of Click boards™, growing on a daily basis. Each section of Clicker 4 is clearly marked, offering an intuitive and clean interface. This makes working with the development
board much simpler and thus, faster. The usability of Clicker 4 doesn’t end with its ability to accelerate the prototyping and application development stages: it is designed as a complete solution which can be implemented directly into any project, with no additional hardware modifications required. Four mounting holes [4.2mm/0.165”] at all four corners allow simple installation by using mounting screws. For most applications, a nice stylish casing is all that is needed to turn the Clicker 4 development board into a fully functional, custom design.
Microcontroller Overview
MCU Card / MCU
Architecture
ARM Cortex-M4
MCU Memory (KB)
256
Silicon Vendor
STMicroelectronics
Pin count
100
RAM (Bytes)
40960
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 CLICKER 4 for STM32F302VCT6 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 NO2 2 Click driver.
Key functions:
no22_read_data- Function for reading ADC datano22_get_ppb- Function for reading ppb datano22_set_pht_state- Function for setting pht pin
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 NO22 Click example
*
* # Description
* Measure the level of NO2
*
* The demo application is composed of two sections :
*
* ## Application Init
* Driver init
*
* ## Application Task
* Measures in span of 1 seconc ppb of NO2
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "no22.h"
// ------------------------------------------------------------------ VARIABLES
static no22_t no22;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
no22_cfg_t cfg;
uint8_t error_data;
/**
* 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.
no22_cfg_setup( &cfg );
NO22_MAP_MIKROBUS( cfg, MIKROBUS_1 );
no22_init( &no22, &cfg );
error_data = no22_set_pht_state( &no22, NO22_PIN_STATE_LOW );
if ( error_data == NO22_DEVICE_ERROR )
{
log_printf( &logger, "Device error \r\n" );
for ( ; ; );
}
log_printf( &logger, "***** App init ***** \r\n" );
}
void application_task ( )
{
uint16_t temp_data_read;
float data_ppb;
temp_data_read = no22_read_data( &no22 );
log_printf( &logger, "ADC: %d \n\r", temp_data_read );
data_ppb = no22_get_ppb( &no22 );
log_printf( &logger, "PPB: %f \r\n", data_ppb );
log_printf( &logger, "___________________________\r\n" );
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:Gas
