Beginner
10 min

Streamline the operation of complex systems with MC74HC165A and ATmega328P

Simplify your control: 16 buttons, 1 masterpiece

4x4 Key Click with Arduino UNO Rev3

Published Feb 14, 2024

Click board™

4x4 Key Click

Dev Board

Arduino UNO Rev3

Compiler

NECTO Studio

MCU

ATmega328P

Maximize space and functionality by choosing our 16-in-1 button integration solution for your control needs

A

A

Hardware Overview

How does it work?

4x4 Key Click is based on 16 buttons with debounce circuits and two MC74HC165A, 8-bit parallel-in/serial-out shift registers from ON Semiconductor. The rightmost column of the keyboard is marked with letters from A to D, while the other 12 buttons are marked like a telephone keypad, so it is easy to implement this 4x4 Click board to any design. The 16-button output lines go straight to the parallel data inputs of the two shift registers connected in a serial (daisy) chain, thus

occupying fewer pins on the host MCU. The shift registers allow you to press all 16 buttons simultaneously, and each will be registered. The 4X4 Click board uses an SPI serial interface to communicate with the host MCU over the mikroBUS™ socket. In this case, the SPI interface saves as many IO pins of the MCU as possible from 16 buttons using shift registers. The Clock Enable pins of the shift registers are not user-configurable and are tied LOW; thus, shift registers are always

enabled. 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.

4x4 Key Click hardware overview image

Features overview

Development board

Arduino UNO is a versatile microcontroller board built around the ATmega328P chip. It offers extensive connectivity options for various projects, featuring 14 digital input/output pins, six of which are PWM-capable, along with six analog inputs. Its core components include a 16MHz ceramic resonator, a USB connection, a power jack, an

ICSP header, and a reset button, providing everything necessary to power and program the board. The Uno is ready to go, whether connected to a computer via USB or powered by an AC-to-DC adapter or battery. As the first USB Arduino board, it serves as the benchmark for the Arduino platform, with "Uno" symbolizing its status as the

first in a series. This name choice, meaning "one" in Italian, commemorates the launch of Arduino Software (IDE) 1.0. Initially introduced alongside version 1.0 of the Arduino Software (IDE), the Uno has since become the foundational model for subsequent Arduino releases, embodying the platform's evolution.

Arduino UNO Rev3 double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

AVR

MCU Memory (KB)

32

Silicon Vendor

Microchip

Pin count

28

RAM (Bytes)

2048

You complete me!

Accessories

Click Shield for Arduino UNO has two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the Arduino UNO board without effort. The Arduino Uno, a microcontroller board based on the ATmega328P, provides an affordable and flexible way for users to try out new concepts and build prototypes with the ATmega328P microcontroller from various combinations of performance, power consumption, and features. The Arduino Uno has 14 digital input/output pins (of which six can be used as PWM outputs), six analog inputs, a 16 MHz ceramic resonator (CSTCE16M0V53-R0), a USB connection, a power jack, an ICSP header, and reset button. Most of the ATmega328P microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the Arduino UNO board with our Click Shield for Arduino UNO, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.

Click Shield for Arduino UNO accessories 1 image

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
SPI Chip Select
PB2
CS
SPI Clock
PB5
SCK
SPI Data OUT
PB4
MISO
SPI Data IN
PB3
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
NC
NC
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Schematic

4x4 Key Click Schematic schematic

Step by step

Project assembly

Click Shield for Arduino UNO front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Arduino UNO Rev3 as your development board.

Click Shield for Arduino UNO front image hardware assembly
Arduino UNO Rev3 front image hardware assembly
Barometer 13 Click front image hardware assembly
Prog-cut hardware assembly
Arduino UNO Rev3 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 image step 5 hardware assembly
Necto image step 6 hardware assembly
Arduino UNO MCU Step hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image Necto Step hardware assembly

Track your results in real time

Application Output

After loading the code example, pressing the "DEBUG" button builds and programs it on the selected setup.

Application Output Step 1

After programming is completed, a header with buttons for various actions available in the IDE appears. By clicking the green "PLAY "button, we start reading the results achieved with Click board™.

Application Output Step 3

Upon completion of programming, the Application Output tab is automatically opened, where the achieved result can be read. In case of an inability to perform the Debug function, check if a proper connection between the MCU used by the setup and the CODEGRIP programmer has been established. A detailed explanation of the CODEGRIP-board connection can be found in the CODEGRIP User Manual. Please find it in the RESOURCES section.

Application Output Step 4

Software Support

Library Description

This library contains API for 4x4 Key Click driver.

Key functions:

  • c4x4key_get_data - Get 16-bit data function.

  • c4x4key_get_btn_position - Get position pressed button function.

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 
 * \brief 4x4Key Click example
 * 
 * # Description
 * The library covers all the necessary functions to control the 4x4 Key Click.
 * 4x4 Key click communicates with the target board via SPI interface. 
 * This library contains drivers for reading data from a sensor and get 
 * the position of the pressed button.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Configuring clicks and log objects.
 * 
 * ## Application Task  
 * This is a example which demonstrates the use of 4x4 Key Click board.
 * Detects and logs whether any of the buttons is pressed.
 * Results are being sent to the Usart Terminal
 * where you can track their changes.
 * All data logs on usb uart when the button is triggered.
 * 
 * \author Nenad Filipovic
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "c4x4key.h"

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

static c4x4key_t c4x4key;
static log_t logger;

static uint16_t btn_data_old;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    c4x4key_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 ----" );

    //  Click initialization.

    c4x4key_cfg_setup( &cfg );
    C4X4KEY_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    c4x4key_init( &c4x4key, &cfg );
    
    btn_data_old = 0;
    
    log_printf( &logger, "   4x4 Key Click\r\n" );
    log_printf( &logger, "--------------------\r\n" );
    log_printf( &logger, "  Press any button\r\n" );
    log_printf( &logger, "--------------------\r\n" );
}

void application_task ( void )
{
    uint16_t btn_data;
    
    btn_data = c4x4key_get_data( &c4x4key );

    if ( btn_data_old != btn_data )
    {
        if ( btn_data == C4X4KEY_BUTTON_0 )
        {
            log_printf( &logger, "         0\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_1 )
        {
            log_printf( &logger, "         1\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_2 )
        {
            log_printf( &logger, "         2\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_3 )
        {
            log_printf( &logger, "         3\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_4 )
        {
            log_printf( &logger, "         4\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_5 )
        {
            log_printf( &logger, "         5\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_6 )
        {
            log_printf( &logger, "         6\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_7 )
        {
            log_printf( &logger, "         7\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_8 )
        {
            log_printf( &logger, "         8\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_9 )
        {
            log_printf( &logger, "         9\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_A )
        {
            log_printf( &logger, "         A\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_B )
        {
            log_printf( &logger, "         B\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_C )
        {
            log_printf( &logger, "         C\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_D )
        {
            log_printf( &logger, "         D\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_STAR )
        {
            log_printf( &logger, "         *\r\n" );
        }
        
        if ( btn_data == C4X4KEY_BUTTON_HASH )
        {
            log_printf( &logger, "         #\r\n" );
        }

        btn_data_old = btn_data;
    }
    Delay_10ms();
}

void main ( void )
{
    application_init( );

    for ( ; ; )
    {
        application_task( );
    }
}


// ------------------------------------------------------------------------ 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.