Intermediate
30 min

Manage multiple functions with our 2x2 keyboard based on 74HC32 and ATmega1284P

Master your controls: 4 buttons, 1 solution

2x2 Key Click with EasyAVR v7

Published Nov 01, 2023

Click board™

2x2 Key Click

Dev Board

EasyAVR v7

Compiler

NECTO Studio

MCU

ATmega1284P

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

A

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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.

2x2 Key Click top side image
2x2 Key Click bottom side image

Features overview

Development board

EasyAVR v7 is the seventh generation of AVR development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 16-bit AVR microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyAVR v7 allows you to connect accessory boards, sensors, and custom electronics more

efficiently than ever. Each part of the EasyAVR v7 development board contains the components necessary for the most efficient operation of the same board. An integrated mikroProg, a fast USB 2.0 programmer with mikroICD hardware In-Circuit Debugger, offers many valuable programming/debugging options and seamless integration with the Mikroe software environment. Besides it also includes a clean and regulated power supply block for the development board. It can use a wide range of external power sources, including an external 12V power supply, 7-12V AC or 9-15V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B)

connector. Communication options such as USB-UART and RS-232 are also included, alongside the well-established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets which cover a wide range of 16-bit AVR MCUs. EasyAVR v7 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.

EasyAVR v7 horizontal image

Microcontroller Overview

MCU Card / MCU

default

Architecture

AVR

MCU Memory (KB)

128

Silicon Vendor

Microchip

Pin count

40

RAM (Bytes)

16384

Used MCU Pins

mikroBUS™ mapper

T1 Button Status
PA7
AN
T2 Button Status
PA6
RST
T3 Button Status
PA5
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
T4 Button Status
PD4
PWM
Interrupt
PD2
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

2x2 Key Click Schematic schematic

Step by step

Project assembly

EasyAVR v7 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyAVR v7 as your development board.

EasyAVR v7 front image hardware assembly
Buck 22 Click front image hardware assembly
MCU DIP 40 hardware assembly
EasyAVR v7 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 DIP image step 7 hardware assembly
EasyPIC PRO v7a Display Selection Necto Step 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 via UART Mode

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

2. After the programming is completed, click on the Tools icon in the upper-right panel, and select the UART Terminal.

3. After opening the UART Terminal tab, first check the baud rate setting in the Options menu (default is 115200). If this parameter is correct, activate the terminal by clicking the "CONNECT" button.

4. Now terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.

UART_Application_Output

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

Additional Support

Resources

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