Beginner
10 min

Achieve unparalleled control over your data flow with 74HC4066D and STM32L496AG

Seamless UART switching: Your data, your way!

UART MUX 4 Click with Discovery kit with STM32L496AG MCU

Published Jul 22, 2025

Click board™

UART MUX 4 Click

Dev. board

Discovery kit with STM32L496AG MCU

Compiler

NECTO Studio

MCU

STM32L496AG

Empower your projects with dynamic UART control – our solution lets you redirect your data flow on the fly, offering a new level of adaptability to suit your project’s communication demands.

A

A

Hardware Overview

How does it work?

UART MUX 4 Click is based on the 74HC4066D, a quad single-pole, single-throw analog switch from Nexperia. The CMOS level inputs of the 74HC4066D include clamp diodes, which in turn allow the use of current limiting resistors to interface inputs to voltages exceeding VCC. This Click board™ has two multiplexed 4-pin UART headers labeled UART1 and UART2. The UART header lines are labeled for corresponding pins. It

offers fast switching speeds with a turn-off time of 13ns and 11ns for turn-on if powered with 5V. The UART MUX 2 Click uses a standard UART interface to communicate with the host MCU, with commonly used RX and TX lines. To switch between the two output UART interfaces, this Click board™ features a switch in the form of an NPN transistor circuit. This switch circuit allows the use of one of the outputs UART interfaces via the

SW pin of the mikroBUS™ socket with a simple logic state. 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.

UART MUX 4 Click hardware overview 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
UART Output Switch
PB2
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
NC
NC
INT
UART TX
PG10
TX
UART RX
PB6
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

UART MUX 4 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
Thermo 21 Click complete accessories setup image 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 UART MUX 4 Click driver.

Key functions:

  • uartmux4_enable_uart1 - UART MUX 4 enable the UART 1 function.

  • uartmux4_enable_uart2 - UART MUX 4 enable the UART 2 function.

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 main.c
 * @brief UART MUX 4 Click Example.
 *
 * # Description
 * This example demonstrates the use of UART MUX 4 Click board by processing
 * the incoming data and displaying them on the USB UART.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the UART driver and additional pins.
 *
 * ## Application Task
 * Writes demo message, echos it back, processes all incoming data 
 * and displays them on the USB UART.
 *
 * @author Nenad Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "uartmux4.h"

#define PROCESS_BUFFER_SIZE 200
#define DEMO_MESSAGE "\r\nMikroE\r\n"

static uartmux4_t uartmux4;
static log_t logger;

static uint8_t app_buf[ PROCESS_BUFFER_SIZE ] = { 0 };

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    uartmux4_cfg_t uartmux4_cfg;  /**< Click config object. */

    /** 
     * 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.
    uartmux4_cfg_setup( &uartmux4_cfg );
    UARTMUX4_MAP_MIKROBUS( uartmux4_cfg, MIKROBUS_1 );
    if ( UART_ERROR == uartmux4_init( &uartmux4, &uartmux4_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    
    log_info( &logger, " Application Task " );
    Delay_ms ( 100 );
}

void application_task ( void ) 
{
    log_printf( &logger, " ---------------- \r\n" );
    log_printf( &logger, " UART 1 demo message:\r\n" );
    uartmux4_enable_uart1( &uartmux4 );
    Delay_ms ( 100 );
    for ( uint8_t n_cnt = 0; n_cnt < 5; n_cnt++ )
    {
        if ( uartmux4_generic_write ( &uartmux4, DEMO_MESSAGE, sizeof( DEMO_MESSAGE ) ) )
        {
            if ( uartmux4_generic_read( &uartmux4, app_buf, sizeof( DEMO_MESSAGE ) ) )
            {
                log_printf( &logger, "%s", app_buf );
            }
        }
        Delay_ms ( 1000 ); 
        Delay_ms ( 1000 );
    }
    
    log_printf( &logger, " ---------------- \r\n" );
    log_printf( &logger, " UART 2 demo message:\r\n" );
    uartmux4_enable_uart2( &uartmux4 );
    Delay_ms ( 100 );
    for ( uint8_t n_cnt = 0; n_cnt < 5; n_cnt++ )
    {
        if ( uartmux4_generic_write ( &uartmux4, DEMO_MESSAGE, sizeof( DEMO_MESSAGE ) ) )
        {
            if ( uartmux4_generic_read( &uartmux4, app_buf, sizeof( DEMO_MESSAGE ) ) )
            {
                log_printf( &logger, "%s", app_buf );
            }
        }
        Delay_ms ( 1000 ); 
        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

Love this project?

'Buy This Kit' button takes you directly to the shopping cart where you can easily add or remove products.