3x4 Keypad wiring/programming

Other Hardware General Electronics
1

i just bought a 3x4 keypad http://www.allspectrum.com/store/12-key-keyboard-common-output-blister-packed-p-1002.html?sdesc=12+KEY+KEYBOARD+-+COMMON+OUTPUT+-+BLISTER-PACKED+Model+%23+12KEY
and im having trouble understanding how it works and how to program it.
ive read Arduino Playground - KeypadTutorial
the keypad i bought has 14 output pins. but according to the keypad tutorial i can use it with 7 pins on the arduino instead of 14. since some of them are linked together. is this true for the keypad i bought?
once i know which numbers on the keypad are connected how do i use that to program it.
i just need a little bit of explanation from this code found in the tutorial

code :

const byte ROWS = 4; // Four rows
const byte COLS = 3; // Three columns
// Define the Keymap
char keys[ROWS][COLS] = {
{'1','2','3'},
{'4','5','6'},
{'7','8','9'},
{'#','0','*'}
};
// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.
byte rowPins[ROWS] = { 9, 8, 7, 6 };
// Connect keypad COL0, COL1 and COL2 to these Arduino pins.
byte colPins[COLS] = { 12, 11, 10 };

the numbers in {9,8,7,6} are the pins in the arduino if im correct.
but what about the numbers that i found out were connected how do i implement that into my program or how can i connect them to those seven pins?

im trying to write a program where i type in a code and light up an LED but just need more clarification with the keypad and how it works

2

The keypad that you bought is not a 'matrix keypad'. Your keypad has a common pin for one side of all of the keys and a separate pin for the other side of each key. In other words there is a separate discrete pin that identifies each key. This makes the programming a lot easier at the expense of using more I/O pins. You can look into solutions that use the analog inputs to read the keypad, but the matrix keypad library won't work.

Don

3

floresta:
The keypad that you bought is not a 'matrix keypad'. Your keypad has a common pin for one side of all of the keys and a separate pin for the other side of each key. In other words there is a separate discrete pin that identifies each key. This makes the programming a lot easier at the expense of using more I/O pins. You can look into solutions that use the analog inputs to read the keypad, but the matrix keypad library won't work.

Don

oh i thought i could since in this website where they sell the product http://www.electronics123.com/s.nl/it.A/id.2205/.f
they have a link to the arduino tutorial. and the keypad used in the tutorial has a 14 pin output but they still program it using seven pins

4

they have a link to the arduino tutorial. and the keypad used in the tutorial has a 14 pin output but they still program it using seven pins

The link is inappropriate for the keypad they are selling. The keypad used in the tutorial has 14 pins but only 7 of them are being used. Your keypad has 14 pins and only 13 of them are being used. The keypads look the same but you still can't use code for a 'matrix keypad' on a keypad with a 'common output'.

Don

5

if i purchase this keypad will it work properly like the one in the tutorial.
i just want to make sure before i buy another one
http://www.allelectronics.com/make-a-store/item/KP-22/12-BUTTON-KEYPAD/1.html

6

will it work properly ...

The wording of your question kind of reminds me of this 'doctor/piano' joke: Aha! Jokes > Medical Jokes > Can I play the piano?, but yes - it should be fine.

Don