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Membrane Keypad (4×4) | NexaLearn IoT Lab | NexaLearn

Input & Control25 دقيقة

Membrane Keypad (4×4)

How to read 16 buttons using only 8 wires.

Lesson Content

Instead of dedicating 16 pins for buttons, the keypad uses a matrix of Rows and Columns. The <Keypad.h> library performs a fast scan: it sends a signal to the first row and reads all columns, then the second row, and so on. This saves half of Arduino's pins.

Components Needed

Arduino Uno4x4 Keypad

Wiring Notes

Connect the eight wires in sequential order to digital pins (e.g., pins 2 through 9).

Code Example

#include <Keypad.h>
const byte ROWS = 4; const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1','2','3','A'}, {'4','5','6','B'}, {'7','8','9','C'}, {'*','0','#','D'}
};
byte rowPins[ROWS] = {9, 8, 7, 6};
byte colPins[COLS] = {5, 4, 3, 2};
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup(){ Serial.begin(9600); }
void loop(){
  char key = keypad.getKey();
  if (key){ Serial.println(key); }
}

Common Mistakes

If numbers appear mirrored (pressing 1 shows 4), reverse the order of the rowPins or colPins arrays.

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