2db 4 gombos mcu billentyűzet Matrix Arduinohoz UNO MEGA2560 DUE gomb málna pi banana pi Kenyérlap kapcsoló FPGA CPLD STM32
2pcs 4 key mcu keyboard Matrix for Arduino UNO MEGA2560 DUE button raspberry pi banana pi Breadboard switch FPGA CPLD STM32
Product Name:2pcs 4 key mcu keyboard push button switch Matrix for Arduiuo UNO MEGA2560 DUE raspberry pi banana pi Breadboard FPGA CPLD STM32 
Packing list(Does not include UNO R3):
 
2 PCS  4 key push button switch;
Description:
Can be inserted directly into Arduiuo uno mega2560 due,Ideal for linking up to your  Arduiuo UNO Mini Nano Mega2560 Breadboard raspberry pi banana pi etc,or others MCU PLD CPU ( AVR STM32 ARM PIC C51 NRF24LE1 CC2530 MSP430 STM8 FPGA CPLD etc.)
1 4-button Common Cathode key module(When pressed output low level).
2 " GND K1 K2 K3 K4" 4 PIN OUT  2.54mm
3  Working voltage: DC 0-48V
4 Size: 12.7MM x 33MM.
Arduiuo uno/mega2560 Code
 
//******************************************************//
/*
Arduiuo_4key_uart
 
This example code is in the public domain.
*/
 
// Define key pin
int K1 = 13;
int K2 = 12;
int K3 = 11;
int K4 = 10;
 
 
// variables will change:
int buttonState = 0; // variable for reading the pushbutton status
 
// the setup routine runs once when you press reset:
void setup() {
// initialize the keys pin as an input.
 
pinMode(K1, INPUT);
pinMode(K2, INPUT);
pinMode(K3, INPUT);
pinMode(K4, INPUT);
 
//Activate key pin internal pull-up resistors
digitalWrite(K1, HIGH);
digitalWrite(K2, HIGH);
digitalWrite(K3, HIGH);
digitalWrite(K4, HIGH);
 
// initialize serial communications at 9600 bps:
Serial.begin(9600);
}
 
// the loop routine runs over and over again forever:
void loop() {
 
buttonState = digitalRead(K1);
if(!buttonState)Serial.print("k1 \n" );
do
{
buttonState = digitalRead(K1);
}
while(!buttonState);//Wait button release
 
buttonState = digitalRead(K2);
if(!buttonState)Serial.print("k2 \n" );
do
{
buttonState = digitalRead(K2);
}
while(!buttonState);//Wait button release
 
buttonState = digitalRead(K3);
if(!buttonState)Serial.print("k3 \n" );
do
{
buttonState = digitalRead(K3);
}
while(!buttonState);//Wait button release
 
buttonState = digitalRead(K4);
if(!buttonState)Serial.print("k4 \n" );
do
{
buttonState = digitalRead(K4);
}
while(!buttonState);//Wait button release
 
delay(100);
}
 
//******************************************************//
 

Circuit schematics : 
 
32282284083 - shop1525466