Intermediate
30 min

Personalized oxygen tracking with VCNL4020C and STM32L496AG

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Oximeter 3 Click with Discovery kit with STM32L496AG MCU

Published Jul 22, 2025

Click board™

Oximeter 3 Click

Dev. board

Discovery kit with STM32L496AG MCU

Compiler

NECTO Studio

MCU

STM32L496AG

Upgrade your solution's health monitoring capabilities with innovative optical pulse oximetry technology

A

A

Hardware Overview

How does it work?

Oximeter 3 Click is based on the VCNL4020C-GS08, a fully integrated biosensor and ambient light sensor with an I2C interface from Vishay Semiconductor. The VCNL4020C-GS08 sensor has a built-in infrared emitter and signal processing IC in a single package with a 16-bit ADC. It also has an ambient light PIN photodiode with close-to-human-eye sensitivity with excellent ambient light suppression through signal modulation. For biosensor functionality, it converts the current from the PIN photodiode to a 16-bit digital data output value, while for ambient light sensing, it converts the current from the ambient light detector, amplifies it, and converts it to a 16-bit digital output stream. The integrated infrared emitter has a peak wavelength of 890nm. It emits light that reflects off an object within 20cm of the sensor and has a programmable drive current from 10mA to 200mA in 10mA steps. The built-in infrared emitter and broader sensitivity

photodiode also can work with the additional onboard green LED and IRLED as designed on this Click board™. As an additional light source, true green color LED (VLMTG1300) with a 525nm peak wavelength is used alongside an infrared dual-color emitting diode (VSMD66694) with 660nm and 940nm peak wavelength well suited for measuring the optical pulse oximetry. The PIN photodiode receives the light reflected off the object and converts it to a current. It has a peak sensitivity of 890nm, matching the peak wavelength of the emitter, and it is insensitive to ambient light. The VCNL4020C also provides ambient light sensing to support conventional backlight and display brightness auto-adjustment. The ambient light sensor receives the visible light and converts it to a current, and it has peak sensitivity at 540nm and bandwidth from 430nm to 610nm. Oximeter 3 Click communicates with the MCU using the standard I2C

2-wire interfacewith a fixed address compatible with all I2C modes (Standard, Fast, and High-Speed).  It allows easy access to a biosensor signal and light intensity measurements without complex calculations or programming. It also generates a programmable interrupt signal routed on the INT pin of the mikroBUS™, which offers Wake-Up functionality for the MCU when a proximity event or ambient light change occurs, which reduces processing overhead by eliminating the need for continuous polling. 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. However, the 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.

Oximeter 3 Click top side image
Oximeter 3 Click lateral side image
Oximeter 3 Click bottom side image

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.

Discovery kit with STM32L496AG MCU double side image

Microcontroller Overview

MCU Card / MCU

STM32L496AG Image

Architecture

ARM Cortex-M4

MCU Memory (KB)

1024

Silicon Vendor

STMicroelectronics

Pin count

169

RAM (Bytes)

327680

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
Interrupt
PH2
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PB8
SCL
I2C Data
PB7
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

Oximeter 3 Click Schematic schematic

Step by step

Project assembly

Discovery kit with STM32H750XB MCU front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Discovery kit with STM32L496AG MCU as your development board.

Discovery kit with STM32H750XB MCU front image hardware assembly
Thermo 21 Click front image hardware assembly
Prog-cut hardware assembly
Board mapper by product7 hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
Necto image step 5 hardware assembly
Necto image step 6 hardware assembly
Discovery kit with STM32H750XB MCU NECTO MCU Selection Step hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto image step 11 hardware assembly

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 Oximeter 3 Click driver.

Key functions:

  • void oximeter3_generic_write ( uint8_t reg_addr, uint8_t write_data ) - Function for writing data to register address.
  • uint8_t oximeter3_generic_read ( uint8_t reg_addr ) - Function for reading data from register address.
  • uint16_t oximeter3_read_value ( uint8_t type_macro ) - Function for reading value from sensor.

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 Oximeter3 Click example
 * 
 * # Description
 * This example demonstrates the use of Oximeter 3 Click board.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes the driver, checks the device ID then configures the device for the selected mode.
 * 
 * ## Application Task  
 * Depending on the selected mode it reads heart rate data (OXIMETER3_HEART_RATE mode) or
 * values of proximity and ambient light sensor (OXIMETER3_PROX or OXIMETER3_ALS modes).
 * All data is being logged on USB UART where you can track their changes.
 * 
 * @note
 * In the case of heart rate, please use a Serial Plot application for data plotting.
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "oximeter3.h"

// ------------------------------------------------------------------ VARIABLES

static oximeter3_t oximeter3;
static log_t logger;

uint8_t dev_mode = 0;
uint16_t rd_val = 0;
uint16_t counter = 2500;

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init ( void )
{
    log_cfg_t log_cfg;
    oximeter3_cfg_t cfg;

    uint8_t dev_status;

    /** 
     * 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.

    oximeter3_cfg_setup( &cfg );
    OXIMETER3_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    oximeter3_init( &oximeter3, &cfg );

    dev_status = oximeter3_generic_read( &oximeter3, OXIMETER3_REG_PRODUCT_ID );
    
    if ( dev_status != OXIMETER3_ID_VAL )
    {
        log_printf( &logger, " *****  ERROR!  ***** \r\n" );
        for ( ; ; );
    }

    dev_mode = OXIMETER3_HEART_RATE;
    
    oximeter3_generic_write( &oximeter3, OXIMETER3_REG_COMMAND,
                                         OXIMETER3_CMD_MEASUREMENT_DISABLE );
    
    oximeter3_generic_write( &oximeter3, OXIMETER3_REG_INTERRUPT_CTRL,
                                         OXIMETER3_INT_STATUS_PROX );
    
    if ( OXIMETER3_HEART_RATE == dev_mode )
    {
        oximeter3_generic_write( &oximeter3, OXIMETER3_REG_LED_CURRENT, 
                                             OXIMETER3_LED_CURR_MID );
        oximeter3_generic_write( &oximeter3, OXIMETER3_REG_PROX_MODULATOR_TIMING,
                                             OXIMETER3_PROX_TIMING_FREQ_390p625_KHZ );
    }
    else
    {
        oximeter3_generic_write( &oximeter3, OXIMETER3_REG_LED_CURRENT, 
                                             OXIMETER3_LED_CURR_MIN );
        oximeter3_generic_write( &oximeter3, OXIMETER3_REG_PROX_MODULATOR_TIMING,
                                             OXIMETER3_PROX_TIMING_FREQ_3p125_MHZ );
    }
    
    oximeter3_generic_write( &oximeter3, OXIMETER3_REG_PROX_RATE,
                                         OXIMETER3_PROX_RATE_250_MPS );

    oximeter3_generic_write( &oximeter3, OXIMETER3_REG_COMMAND,
                                         OXIMETER3_CMD_MEASUREMENT_ENABLE |
                                         OXIMETER3_CMD_PROX_PERIODIC_MEASUREMENT_ENABLE |
                                         OXIMETER3_CMD_ALS_PERIODIC_MEASUREMENT_ENABLE );

    log_printf( &logger, " ***** APP TASK ***** \r\n" );
}

void application_task ( void )
{
    if ( OXIMETER3_HEART_RATE == dev_mode )
    {
        if( !oximeter3_get_int_status( &oximeter3 ) )
        {
            rd_val = oximeter3_read_value( &oximeter3, OXIMETER3_PROX );
            oximeter3_generic_write( &oximeter3, OXIMETER3_REG_INTERRUPT_STATUS, 
                                                 OXIMETER3_INT_STATUS_PROX );
            
            counter++;
            if ( rd_val > 10000 )
            {
                log_printf( &logger, "%u\r\n", rd_val );
                counter = 2500;
            }
            else if ( counter > 2500 )
            {
                log_printf( &logger, "Please place your index finger on the sensor.\r\n" );
                counter = 0;
            }
        }
    }
    else if ( OXIMETER3_PROX == dev_mode || OXIMETER3_ALS == dev_mode )
    {
        if( !oximeter3_get_int_status( &oximeter3 ) )
        {
            rd_val = oximeter3_read_value( &oximeter3, OXIMETER3_PROX );
            oximeter3_generic_write( &oximeter3, OXIMETER3_REG_INTERRUPT_STATUS, 
                                                 OXIMETER3_INT_STATUS_PROX );
            
            log_printf( &logger, " * Proximity: %u \r\n", rd_val );
        
            rd_val = oximeter3_read_value( &oximeter3, OXIMETER3_ALS );
            log_printf( &logger, " * ALS: %u \r\n", rd_val );
            
            log_printf( &logger, "******************** \r\n" );
            
            Delay_ms ( 500 );
        }
    }
}

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

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