Manage multiple functions with our 2x2 keyboard based on 74HC32 and STM32F407VGT6

Master your controls: 4 buttons, 1 solution

2x2 Key Click with Clicker 4 for STM32F4

Published Dec 29, 2023

Click board™

2x2 Key Click

Dev Board

Clicker 4 for STM32F4

Compiler

NECTO Studio

MCU

STM32F407VGT6

Our purpose is to maximize functionality while minimizing complexity with our 4-in-1 button integration

Hardware Overview

How does it work?

2x2 Key Click is based on the 2x2 button keyboard with debounce circuit, composed of the 74HC32, a quad 2-input OR gate from Nexperia, and the SN74HC14, a Hex Schmitt-Trigger inverter from Texas Instruments. In electronics, two metal components bounce or create multiple signals when they are in contact with each other — like when you push a button — before they reach a stable state. You want a single contact to be recorded, but the microcontroller records this as if you pressed the button many times. So debouncing is, as the name states, the removal of bounces or spikes of low and high voltages.

Graphically speaking, you want a clean line, not spikes. A debounce circuit makes sure that there are no voltage changes on the output. Thanks to it, one button press is recorded as such. All four Schmitt-trigger outputs are connected to the logic OR gate 74HC32 input pins, whose output is directly connected to the INT pin on mikroBUS. This pin is used to signalize an interrupt to the MCU any time a button is pressed. This way, the MCU software can be implemented as a simple polling routine without any delays programmed in the code (like it would be necessary if there weren’t a hardware debouncing circuit present).

Thanks to the INT pin, you can easily program a common interrupt service routine to detect when a button is pressed (the state of the button changes from low to high logic level). 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.

Features overview

Development board

Clicker 4 for STM32F4 is a compact development board designed as a complete solution that you can use to quickly build your own gadgets with unique functionalities. Featuring an STM32F407VGT6 MCU, four mikroBUS™ sockets for Click boards™ connectivity, power management, and more, it represents a perfect solution for the rapid development of many different types of applications. At its core is an STM32F407VGT6 MCU, a powerful microcontroller by STMicroelectronics based on the high-performance

Arm® Cortex®-M4 32-bit processor core operating at up to 168 MHz frequency. It provides sufficient processing power for the most demanding tasks, allowing Clicker 4 to adapt to any specific application requirements. Besides two 1x20 pin headers, four improved mikroBUS™ sockets represent the most distinctive connectivity feature, allowing access to a huge base of Click boards™, growing on a daily basis. Each section of Clicker 4 is clearly marked, offering an intuitive and clean interface. This makes working with the

development board much simpler and, thus, faster. The usability of Clicker 4 doesn’t end with its ability to accelerate the prototyping and application development stages: it is designed as a complete solution that can be implemented directly into any project, with no additional hardware modifications required. Four mounting holes [4.2mm/0.165”] at all four corners allow simple installation by using mounting screws.

Microcontroller Overview

MCU Card / MCU

Architecture

ARM Cortex-M4

MCU Memory (KB)

Silicon Vendor

STMicroelectronics

Pin count

100

RAM (Bytes)

100

Used MCU Pins

mikroBUS™ mapper

T1 Button Status

PC4

T2 Button Status

PC15

RST

T3 Button Status

PA4

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

T4 Button Status

PE9

PWM

Interrupt

PD0

INT

SCL

SDA

Power Supply

Ground

GND

Take a closer look

Schematic

Step by step

Project assembly

Clicker 4 for STM32F4 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Clicker 4 for STM32F4 as your development board.

Rotary O 2 Click front image hardware assembly

Clicker 4 STM32F4 MB 1 - upright/background hardware assembly

Clicker 4 for STM32F4 HA MCU Step hardware assembly

Necto No Display image step 8 hardware assembly

Debug Image Necto Step hardware assembly

Track your results in real time

Application Output via Debug Mode

1. Once the code example is loaded, pressing the "DEBUG" button initiates the build process, programs it on the created setup, and enters Debug mode.

2. After the programming is completed, a header with buttons for various actions within the IDE becomes visible. Clicking the green "PLAY" button starts reading the results achieved with the Click board™. The achieved results are displayed in the Application Output tab.

Software Support

Library Description

This library contains API for 2x2 Key Click driver.

Key functions:

c2x2key_t1_state - This function gets state of AN pin
c2x2key_t2_state - This function gets state of RST pin
c2x2key_t3_state - This function gets state of CS pin
c2x2key_t4_state - This function gets state of PWM pin

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 2x2 key Click example
 * 
 * # Description
 * 2x2 Key click has a 4 button keypad and allows multiple key presses.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Application Init performs Logger and Click initialization.
 * 
 * ## Application Task  
 * This example code demonstrates the usage of 2X2 Key Click board.
 * Detects whether any of the keys is pressed where results are being sent 
 * to the UART terminal where you can track changes.
 * 
 * \author Mihajlo Djordjevic
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "c2x2key.h"

uint8_t t1_state     = 0;
uint8_t t1_state_old = 1;
uint8_t t2_state     = 0;
uint8_t t2_state_old = 1;
uint8_t t3_state     = 0;
uint8_t t3_state_old = 1;
uint8_t t4_state     = 0;
uint8_t t4_state_old = 1;

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

static c2x2key_t c2x2key;
static log_t logger;

// ------------------------------------------------------- ADDITIONAL FUNCTIONS


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

void application_init ( void )
{
    log_cfg_t log_cfg;
    c2x2key_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_printf( &logger, "-- Application  Init --\r\n" );
    Delay_ms ( 1000 );

    //  Click initialization.

    c2x2key_cfg_setup( &cfg );
    C2X2KEY_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    c2x2key_init( &c2x2key, &cfg );
    
    log_printf( &logger, "-----------------------\r\n" );
    log_printf( &logger, "     2X2 key Click     \r\n" );
    log_printf( &logger, "-----------------------\r\n" );
    Delay_ms ( 1000 );
    
    log_printf( &logger, "    System is ready    \r\n" );
    log_printf( &logger, "-----------------------\r\n" );
    Delay_ms ( 1000 );
}

void application_task ( void )
{
   t1_state = c2x2key_t1_state( &c2x2key );
   
   if ( ( t1_state == 1 ) && ( t1_state_old == 0 ) )
    {
        log_printf( &logger, "-----------------------\r\n" );
        log_printf( &logger, "     Key 1 pressed     \r\n" );
        log_printf( &logger, "-----------------------\r\n" );
        t1_state_old = 1;
    }
    
    if ( ( t1_state == 0 ) && ( t1_state_old == 1 ) )
    {
        t1_state_old = 0;
    }
    
    t2_state = c2x2key_t2_state( &c2x2key );
   
   if ( ( t2_state == 1 ) && ( t2_state_old == 0 ) )
    {
        log_printf( &logger, "-----------------------\r\n" );
        log_printf( &logger, "     Key 2 pressed     \r\n" );
        log_printf( &logger, "-----------------------\r\n" );
        t2_state_old = 1;
    }
    
    if ( ( t2_state == 0 ) && ( t2_state_old == 1 ) )
    {
        t2_state_old = 0;
    }
    
    t3_state = c2x2key_t3_state( &c2x2key );
   
   if ( ( t3_state == 1 ) && ( t3_state_old == 0 ) )
    {
        log_printf( &logger, "-----------------------\r\n" );
        log_printf( &logger, "     Key 3 pressed     \r\n" );
        log_printf( &logger, "-----------------------\r\n" );
        t3_state_old = 1;
    }
    
    if ( ( t3_state == 0 ) && ( t3_state_old == 1 ) )
    {
        t3_state_old = 0;
    }
    
    t4_state = c2x2key_t4_state( &c2x2key );
   
   if ( ( t4_state == 1 ) && ( t4_state_old == 0 ) )
    {
        log_printf( &logger, "-----------------------\r\n" );
        log_printf( &logger, "     Key 4 pressed     \r\n" );
        log_printf( &logger, "-----------------------\r\n" );
        t4_state_old = 1;
    }
    
    if ( ( t4_state == 0 ) && ( t4_state_old == 1 ) )
    {
        t4_state_old = 0;
    }
}

void main ( void )
{
    application_init( );

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

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