10 min

Provide clear visual feedback and signal knob's position with EC12D1564402 and STM32F746ZG

Symphony of motion and light

ROTARY B Click with Fusion for STM32 v8

Published Jun 22, 2023

Click board™


Development board

Fusion for STM32 v8


NECTO Studio



Our cutting-edge rotary solution embraces a striking blue LED ring, defining your every move



Hardware Overview

How does it work?

ROTARY B Click is based on two SN74HC595 SPI-configurable 8-bit shift registers from Texas Instruments that, 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 blue 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 SN74HC595 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 SN74HC595 also has a Reset feature used across the RST mikroBUS™ line. This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the PWR SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to 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.

ROTARY B Click hardware overview image

Features overview

Development board

Fusion for STM32 v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different 32-bit ARM® Cortex®-M based MCUs from STMicroelectronics, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, Fusion for STM32 v8 provides a fluid and immersive working experience, allowing

access anywhere and under any circumstances at any time. Each part of the Fusion for STM32 v8 development board contains the components necessary for the most efficient operation of the same board. An advanced integrated CODEGRIP programmer/debugger module offers many valuable programming/debugging options, including support for JTAG, SWD, and SWO Trace (Single Wire Output)), and seamless integration with the Mikroe software environment. Besides, it also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector.

Communication options such as USB-UART, USB HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet is also included. In addition, it also has the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options for the TFT board line of products and character-based LCD. Fusion for STM32 v8 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

Fusion for STM32 v8 horizontal image

Microcontroller Overview

MCU Card / MCU



8th Generation


ARM Cortex-M7

MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

Encoder Output B
SPI Chip Select
SPI Clock
Power Supply
Encoder Output A
Knob Detection
Power Supply

Take a closer look


ROTARY B Click Schematic schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Fusion for STM32 v8 as your development board.

Fusion for PIC v8 front image hardware assembly
GNSS2 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
v8 SiBRAIN Access MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
NECTO Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image hardware assembly

Track your results in real time

Application Output

After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.

UART Application Output Step 1

Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.

UART Application Output Step 2

In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".

UART Application Output Step 3

The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.

UART Application Output Step 4

Software Support

Library Description

This library contains API for ROTARY B Click driver.

Key functions:

  • rotaryb_generic_transfer - ROTARY B data transfer function.

  • rotaryb_turn_on_led_by_position - Function turn on led by position

  • rotaryb_button_push - Function return 1 if button is pushed and return 0 if not

Open Source

Code example

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

 * @file main.c
 * @brief Rotary Y Click example
 * # Description
 * The demo application controls led on click with rotary 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 Y Click, rotating and turn on/off led's,
 * using the SPI interface.
 * @note
 * In orther to use all of the clicks functionality, pull down INT pin.
 * @author Stefan Ilic

#include "board.h"
#include "log.h"
#include "rotaryy.h"

static rotaryy_t rotaryy;
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. */
    rotaryy_cfg_t rotaryy_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.

    rotaryy_cfg_setup( &rotaryy_cfg );
    ROTARYY_MAP_MIKROBUS( rotaryy_cfg, MIKROBUS_1 );
    err_t init_flag  = rotaryy_init( &rotaryy, &rotaryy_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 ) {
    rotaryy_turn_on_led_by_data( &rotaryy, led_data );

//     Push button
    if ( rotaryy_button_push( &rotaryy ) ) {
        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++ ) {
                    rotaryy_turn_on_led_by_data( &rotaryy, 0xAAAA );
                    Delay_ms( 100 );
                    rotaryy_turn_on_led_by_data( &rotaryy, 0x5555 );
                    Delay_ms( 100 );

                for ( old_state = 0; old_state < 17; old_state++ ) {
                    rotaryy_turn_on_led_by_position( &rotaryy, old_state );
                    Delay_ms( 100 );

                led_state = 0;
                led_data = rotaryy_get_led_data( led_state );
            else {
                led_data = rotaryy_get_led_data( led_state );
    else {
        old_state = 0;

//     Rotate Clockwise and CounterClockwise
    if ( rotaryy_get_eca_state( &rotaryy ) == rotaryy_get_ecb_state( &rotaryy ) ) {
        old__rot_state = 0;
        start_status = rotaryy_get_eca_state( &rotaryy ) && rotaryy_get_ecb_state( &rotaryy );
    else {
        new_rotate_state = 1;
        if ( new_rotate_state != old__rot_state ) {
            old__rot_state = 1;
            if ( start_status != rotaryy_get_eca_state( &rotaryy ) ) {
                led_data = ( led_data << 1 ) | ( led_data >> 15 );
            else {
                led_data = ( led_data >> 1 ) | ( led_data << 15 );

void main ( void ) {
    application_init( );

    for ( ; ; ) {
        application_task( );

// ------------------------------------------------------------------------ END

Additional Support