Beginner
10 min

Embark on a creative journey of user interface enhancement with EC12D1564402 and STM32L496AG

Bring precision and visual appeal to your electronic designs

ROTARY O Click with Discovery kit with STM32L496AG MCU

Published Jul 22, 2025

Click board™

ROTARY O Click

Dev. board

Discovery kit with STM32L496AG MCU

Compiler

NECTO Studio

MCU

STM32L496AG

Uncover the magic of this compact add-on board, combining rotary input control and dynamic LED lighting for captivating user experiences

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Hardware Overview

How does it work?

Rotary O Click is based on two 74HC595 SPI-configurable 8-bit shift registers from Texas Instruments. Combined with a high-quality rotary encoder, the EC12D1564402 allows you to add a precision input knob to your design. The EC12D1564402 incremental rotary encoder is surrounded by a ring of 16 orange LEDs where a single rotation is divided into 15 discrete steps (in contrast to a potentiometer, a rotary encoder can be spun around continuously). This Click board™ is an ideal solution for building various HMI applications where precise input is required, but also for some interesting visual effects to any application. As mentioned, this Click board™ uses the EC12D1564402, a 15-pulse incremental rotary

encoder with a push-button, from ALPS. This encoder has unique mechanical specifications (debouncing time for its internal switches goes down to 2ms) and can withstand many switching cycles, up to 30.000. The supporting debouncing circuitry allows contacts to settle before the output is triggered fully. The 74HC595 controls each LED individually positioned in a ring around the encoder through a standard SPI interface with a maximum frequency of 5MHz. Rotating the encoder, it outputs A and B signals (out of phase to each other) on the two mikroBUS™ lines, AN and PWM pins of the mikroBUS™ socket, alongside the push-button contact, which outputs through the interrupt line of the mikroBUS™

socket. The 74HC595 also has a Reset feature used across the RST mikroBUS™ line. Finally, the Rotary O Click uses the 74LVC1T45, a single-bit, dual-power supply translating transceiver with three state outputs from Diodes Incorporated for rotary encoder voltage logic translation. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the PWR 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.

ROTARY O Click top side image
ROTARY O 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

Encoder Output B
PA4
AN
Reset
PB2
RST
SPI Chip Select
PG11
CS
SPI Clock
PI1
SCK
SPI Data OUT
PD3
MISO
SPI Data IN
PI3
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
Encoder Output A
PA0
PWM
Knob Detection
PH2
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
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Take a closer look

Click board™ Schematic

ROTARY O 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

Software Support

Library Description

This library contains API for ROTARY O Click driver.

Key functions:

  • rotaryo_generic_transfer - ROTARY data transfer function

  • rotaryo_turn_on_led_by_data - Function turn on led by data

  • rotaryo_turn_on_led_by_position - Function turn on led by position

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 Rotary O Click example
 *
 * # Description
 * The demo application controls led on Click with rotory on board
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes SPI driver, set initial states, 
 * set RST logic high and performs device configuration.
 *
 * ## Application Task
 * Show functionality of Rotary O Click, rotating and turn on/off led's,
 * using the SPI interface
 *
 * @note
 * In order to use all of the Clicks functionality, pull down INT pin.
 *
 * @author Stefan Ilic
 *
 */

#include "board.h"
#include "log.h"
#include "rotaryo.h"

static rotaryo_t rotaryo;
static log_t logger;

static uint8_t start_status;
static uint8_t old_state;
static uint8_t new_state;
static uint8_t old__rot_state;
static uint8_t new_rotate_state;
static uint8_t led_state;
static uint16_t led_data;

void application_init ( void ) {
    log_cfg_t log_cfg;  /**< Logger config object. */
    rotaryo_cfg_t rotaryo_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.

    rotaryo_cfg_setup( &rotaryo_cfg );
    ROTARYO_MAP_MIKROBUS( rotaryo_cfg, MIKROBUS_1 );
    err_t init_flag  = rotaryo_init( &rotaryo, &rotaryo_cfg );
    if ( init_flag == SPI_MASTER_ERROR ) {
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );

        for ( ; ; );
    }

    log_info( &logger, " Application Task " );
    
    led_data = 0x0001;
    old_state = 0;
    new_state = 1;
    old__rot_state = 0;
    new_rotate_state = 1;
}

void application_task ( void ) {
    rotaryo_turn_on_led_by_data( &rotaryo, led_data );

//     Push button
    if ( rotaryo_button_push( &rotaryo ) ) {
        new_state = 1;
        if ( new_state == 1 && old_state == 0 ) {
            old_state = 1;
            led_state = ( led_state + 1 ) % 5;
            if ( led_state == 4 ) {
                for ( old_state = 0; old_state < 17; old_state++ ) {
                    rotaryo_turn_on_led_by_data( &rotaryo, 0xAAAA );
                    Delay_ms ( 100 );
                    rotaryo_turn_on_led_by_data( &rotaryo, 0x5555 );
                    Delay_ms ( 100 );
                }

                for ( old_state = 0; old_state < 17; old_state++ ) {
                    rotaryo_turn_on_led_by_position( &rotaryo, old_state );
                    Delay_ms ( 100 );
                }

                led_state = 0;
                led_data = rotaryo_get_led_data( led_state );
            }
            else {
                led_data = rotaryo_get_led_data( led_state );
            }
        }
    }
    else {
        old_state = 0;
    }

//     Rotate Clockwise and CounterClockwise
    if ( rotaryo_get_eca_state( &rotaryo ) == rotaryo_get_ecb_state( &rotaryo ) ) {
        old__rot_state = 0;
        start_status = rotaryo_get_eca_state( &rotaryo ) && rotaryo_get_ecb_state( &rotaryo );
    }
    else {
        new_rotate_state = 1;
        if ( new_rotate_state != old__rot_state ) {
            old__rot_state = 1;
            if ( start_status != rotaryo_get_eca_state( &rotaryo ) ) {
                led_data = ( led_data << 1 ) | ( led_data >> 15 );
            }
            else {
                led_data = ( led_data >> 1 ) | ( led_data << 15 );
            }
        }
    }
}

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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