Using a 3×4 Keypad

Ever want to use a 3×4 Keypad? These keypads from Adafruit can be used for numeric data entry or for access control for a security system. Our example allows you to input a multiple digit entry with a “enter key” (#) and a “cancel key” (*). In our example, we will assemble a file name for submission to a sd card, but you can drop that off if you don’t need that.

I plugged the keypad cable into a male extended length header, and plugged in directly into pins 2-8 on the arduino.

Download the library file at http://playground.arduino.cc/Code/Keypad and install into your library folder.

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The following sketch will allow a key sequence of  at least 6 digits. You can enlarge the string if you need more digits. It displays each digit as entered in the serial monitor,and allows you to press * to cancel and start over if you make a mistake.

Thanks to Mike McRoberts and Mark Stanley for their help!

Also see our RFId and Fingerprint scanner tutorials!

#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 3; //three columns
char keys[ROWS][COLS] = {
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};
byte rowPins[ROWS] = {8, 7, 6, 5}; //connect to the row pinouts of the kpd
byte colPins[COLS] = {4, 3, 2}; //connect to the column pinouts of the kpd

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

char entryStr[8];
int i=0;

void setup(){
Serial.begin(9600);
}

void loop(){
char key = keypad.getKey();

if (key){
if (key == ‘*’){
memset(entryStr, 0, sizeof(entryStr));
i=0;
key=0;
Serial.println(“”);
Serial.println(“Canceled”);

} else if (key != ‘#’){
entryStr[i]= key;
i++;
Serial.print(key);
}
else {
Serial.println(“”);
i=0;
key=0;

String fileName = entryStr;
memset(entryStr, 0, sizeof(entryStr));
fileName = fileName + “.mp3”;
Serial.println(fileName);
}

}
}

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