Accurate alcohol detection based on the MiCS-5524 and STM32L496AG
Alcohol awareness simplified: Our detection, your safe passage
Published Jul 22, 2025
Click board™
Alcohol 3 Click
Dev. board
Discovery kit with STM32L496AG MCU
Compiler
NECTO Studio
MCU
STM32L496AG
Develop top-of-the-line alcohol breath tester and early fire and gas leakage detection applications easily
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Hardware Overview
How does it work?
Alcohol 3 Click is based on the MiCS-5524 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-5524 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. This should be considered, especially when
developing applications for estimating blood alcohol content (BAC) from a breath sample (also known as a breathalyzer). The MiCS-5524 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 datasheet of the MiCS-5524 sensor offers typical values for its resistance when used in clean air (artificial conditions). The sensitivity is then expressed as the ratio between the sensor's resistance in clean air and resistance at a concentration of 60 ppm CO. The middle tap between the sensor (as a resistor) and the fixed resistance provides an output voltage. It depends on the sensor's resistance, allowing it to be used as the input into the MCP3221, 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 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
The 32L496GDISCOVERY Discovery kit serves as a comprehensive demonstration and development platform for the STM32L496AG microcontroller, featuring an Arm® Cortex®-M4 core. Designed for applications that demand a balance of high performance, advanced graphics, and ultra-low power consumption, this kit enables seamless prototyping for a wide range of embedded solutions. With its innovative energy-efficient
architecture, the STM32L496AG integrates extended RAM and the Chrom-ART Accelerator, enhancing graphics performance while maintaining low power consumption. This makes the kit particularly well-suited for applications involving audio processing, graphical user interfaces, and real-time data acquisition, where energy efficiency is a key requirement. For ease of development, the board includes an onboard ST-LINK/V2-1
debugger/programmer, providing a seamless out-of-the-box experience for loading, debugging, and testing applications without requiring additional hardware. The combination of low power features, enhanced memory capabilities, and built-in debugging tools makes the 32L496GDISCOVERY kit an ideal choice for prototyping advanced embedded systems with state-of-the-art energy efficiency.
Microcontroller Overview
MCU Card / MCU
Architecture
ARM Cortex-M4
MCU Memory (KB)
1024
Silicon Vendor
STMicroelectronics
Pin count
169
RAM (Bytes)
327680
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 Discovery kit with STM32L496AG 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 Alcohol 3 Click driver.
Key functions:
alcohol3_get_co_in_ppm- This function reads CO (Carbon monoxide) data in ppm (1 ppm - 1000 ppm)alcohol3_get_percentage_bac- This function reads percentage of alcohol in the blood (BAC)alcohol3_get_adc_data- This function reads 12bit ADC value.
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 Alcohol3 Click example
*
* # Description
* Code of this sensor reacts to the presence of deoxidizing and reducing gases,
* such as ethanol (also known as alcohol).
*
* The demo application is composed of two sections :
*
* ## Application Init
* Application Init performs Logger and Click initialization.
*
* ## Application Task
* Reads percentage of alcohol in the blood (BAC)
* and this data logs to USBUART every 1 sec.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "alcohol3.h"
// ------------------------------------------------------------------ VARIABLES
static alcohol3_t alcohol3;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
alcohol3_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 ----" );
Delay_ms ( 100 );
// Click initialization.
alcohol3_cfg_setup( &cfg );
ALCOHOL3_MAP_MIKROBUS( cfg, MIKROBUS_1 );
alcohol3_init( &alcohol3, &cfg );
log_printf( &logger, "--------------------------\r\n\n" );
log_printf( &logger, " ---- Alcohol 3 Click ----\r\n" );
log_printf( &logger, "--------------------------\r\n\n" );
Delay_ms ( 1000 );
log_printf( &logger, " ---- Initialization ---\r\n" );
log_printf( &logger, "--------------------------\r\n\n" );
Delay_ms ( 1000 );
}
void application_task ( void )
{
uint16_t co_ppm;
uint16_t p_bac;
float temp_bac;
// Task implementation.
log_printf( &logger, " --- Alcohol diagnostics ---- \r\n" );
co_ppm = alcohol3_get_co_in_ppm ( &alcohol3 );
log_printf( &logger, " co in ppm %d | \r\n", co_ppm );
temp_bac = alcohol3_get_percentage_bac( &alcohol3 );
p_bac = ( uint16_t )( temp_bac * 1000 );
if ( 10 > p_bac && p_bac < 100 )
{
log_printf( &logger, " BAC | 0.00%d\r\n", p_bac );
}
else if ( 100 <= p_bac && 1000 > p_bac )
{
log_printf( &logger, " BAC | 0.0%d\r\n", p_bac );
}
else if ( p_bac >= 1000 )
{
log_printf( &logger, " BAC | 0.%d\r\n", p_bac );
}
else
{
log_printf( &logger, " BAC | 0.0000\r\n" );
}
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
