Our purpose is to maximize functionality while minimizing complexity with our 4-in-1 button integration
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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.
Features overview
Development board
Nucleo-144 with STM32F413ZH MCU board offers an accessible and adaptable avenue for users to explore new ideas and construct prototypes. It allows users to tailor their experience by selecting from a range of performance and power consumption features offered by the STM32 microcontroller. With compatible boards, the
internal or external SMPS dramatically decreases power usage in Run mode. Including the ST Zio connector, expanding ARDUINO Uno V3 connectivity, and ST morpho headers facilitate easy expansion of the Nucleo open development platform. The integrated ST-LINK debugger/programmer enhances convenience by
eliminating the need for a separate probe. Moreover, the board is accompanied by comprehensive free software libraries and examples within the STM32Cube MCU Package, further enhancing its utility and value.
Microcontroller Overview
MCU Card / MCU

Architecture
ARM Cortex-M4
MCU Memory (KB)
1536
Silicon Vendor
STMicroelectronics
Pin count
144
RAM (Bytes)
327680
You complete me!
Accessories
Click Shield for Nucleo-144 comes equipped with four mikroBUS™ sockets, with one in the form of a Shuttle connector, allowing all the Click board™ devices to be interfaced with the STM32 Nucleo-144 board with no effort. This way, MIKROE allows its users to add any functionality from our ever-growing range of Click boards™, such as WiFi, GSM, GPS, Bluetooth, ZigBee, environmental sensors, LEDs, speech recognition, motor control, movement sensors, and many more. Featuring an ARM Cortex-M microcontroller, 144 pins, and Arduino™ compatibility, the STM32 Nucleo-144 board offers limitless possibilities for prototyping and creating diverse applications. These boards are controlled and powered conveniently through a USB connection to program and efficiently debug the Nucleo-144 board out of the box, with an additional USB cable connected to the USB mini port on the board. Simplify your project development with the integrated ST-Link debugger and unleash creativity using the extensive I/O options and expansion capabilities. 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 STM32 Nucleo-144 board with our Click Shield for Nucleo-144, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Click board™ Schematic

Step by step
Project assembly
Track your results in real time
Application Output
1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support
Library Description
This library contains API for 2x2 Key Click driver.
Key functions:
c2x2key_t1_state
- This function gets state of AN pinc2x2key_t2_state
- This function gets state of RST pinc2x2key_t3_state
- This function gets state of CS pinc2x2key_t4_state
- This function gets state of PWM pin
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
* \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;
}
}
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