Interface 4×4 Keypad With Raspberry Pi

Let's try keypad on Raspberry Pi!

Introduction

If you’re developing project that require control panel, keypad can be one of the important component. So, in this tutorial, I will share on how to interface keypad with Raspberry Pi.

Video

This video will show you how to interface 4×4 keypad with Raspberry Pi and create a simple password application.

Hardware Preparation

This is the list of items used in the video

Wiring connection table.

Raspberry Pi/Maker pHATKeypad 4×4I2C LCD
GNDGND
5VVCC
SDASDA
SCLSCL
GPIO171 (most left)
GPIO182
GPIO273
GPIO224
GPIO255
GPIO126
GPIO137
GPIO198 (most right)

Sample Program

This is sample program to interface keypad with Raspberry Pi. It has 2 files, (1) Main file and (2) Library for I2C LCD.

from gpiozero import DigitalInputDevice, DigitalOutputDevice, Buzzer
from time import time, sleep
import I2C_LCD_driver
col1 = DigitalOutputDevice(17)
col2 = DigitalOutputDevice(18)
col3 = DigitalOutputDevice(27)
col4 = DigitalOutputDevice(22)
row1 = DigitalInputDevice(25, pull_up=None, active_state=True)
row2 = DigitalInputDevice(12, pull_up=None, active_state=True)
row3 = DigitalInputDevice(13, pull_up=None, active_state=True)
row4 = DigitalInputDevice(19, pull_up=None, active_state=True)
buzzer = Buzzer(26)
lcd = I2C_LCD_driver.lcd()
def scanCol(colNumber):
if colNumber == 0:
col1.on()
col2.off()
col3.off()
col4.off()
elif colNumber == 1:
col1.off()
col2.on()
col3.off()
col4.off()
elif colNumber == 2:
col1.off()
col2.off()
col3.on()
col4.off()
elif colNumber == 3:
col1.off()
col2.off()
col3.off()
col4.on()
def row1Pressed():
global colNumber
global keypadNumber
global scanning
if col1.value == 1:
keypadNumber = 1
elif col2.value == 1:
keypadNumber = 2
elif col3.value == 1:
keypadNumber = 3
elif col4.value == 1:
keypadNumber = 10
scanning = False
def row2Pressed():
global colNumber
global keypadNumber
global scanning
if col1.value == 1:
keypadNumber = 4
elif col2.value == 1:
keypadNumber = 5
elif col3.value == 1:
keypadNumber = 6
elif col4.value == 1:
keypadNumber = 11
scanning = False
def row3Pressed():
global colNumber
global keypadNumber
global scanning
if col1.value == 1:
keypadNumber = 7
elif col2.value == 1:
keypadNumber = 8
elif col3.value == 1:
keypadNumber = 9
elif col4.value == 1:
keypadNumber = 12
scanning = False
def row4Pressed():
global colNumber
global keypadNumber
global scanning
if col1.value == 1:
keypadNumber = 14
elif col2.value == 1:
keypadNumber = 0
elif col3.value == 1:
keypadNumber = 15
elif col4.value == 1:
keypadNumber = 13
scanning = False
def row1Released():
global scanning
scanning = True
def row2Released():
global scanning
scanning = True
def row3Released():
global scanning
scanning = True
def row4Released():
global scanning
scanning = True
row1.when_activated = row1Pressed
row2.when_activated = row2Pressed
row3.when_activated = row3Pressed
row4.when_activated = row4Pressed
row1.when_deactivated = row1Released
row2.when_deactivated = row2Released
row3.when_deactivated = row3Released
row4.when_deactivated = row4Released
currentMillis = 0
previousMillis = 0
interval = 10
colNumber = 0
keypadNumber = 20
scanning = True
passCount = 0
passTimeout = 0
password = "123456"
passEnter = ""
lcd.lcd_display_string("Please enter ", 1, 0)
lcd.lcd_display_string("Password:", 2, 0)
buzzer.beep(0.1, 0.1, 1)
try:
while True:
currentMillis = time() * 1000
if currentMillis previousMillis > interval and scanning == True:
previousMillis = currentMillis
scanCol(colNumber)
colNumber = colNumber+1
if colNumber == 4:
colNumber = 0
if passCount:
passTimeout = passTimeout+1
if passTimeout > 200:
if passEnter == password:
lcd.lcd_display_string("CORRECT! Pls etr", 1, 0)
buzzer.beep(0.05, 0.05, 2)
else:
lcd.lcd_display_string("WRONG! Try again", 1, 0)
buzzer.beep(0.2, 0.2, 3)
passEnter = ""
passCount = 0
lcd.lcd_display_string(" ", 2, 9)
if passCount == 1 and passTimeout == 1:
lcd.lcd_display_string("Scanning… ", 1, 0)
if keypadNumber < 20:
print(keypadNumber)
if keypadNumber < 10 and passCount < 6:
passEnter = passEnter + str(keypadNumber)
lcd.lcd_display_string(passEnter, 2, 9)
buzzer.beep(0.05, 0.05, 1)
passCount = passCount+1
passTimeout = 0
keypadNumber = 20
except KeyboardInterrupt:
lcd.lcd_clear()

https://gist.github.com/IdrisCytron/6cde591d59dc14eb4149dc38f63d9bdd

Thank You

References:

  1. Raspberry Pi gpiozero library
  2. How to Display on I2C LCD Using Raspberry Pi

Thanks for reading this tutorial. If you have any technical inquiry, please post at Cytron Technical Forum.

2 thoughts on “Interface 4×4 Keypad With Raspberry Pi”

  1. I’m having the same issue. I get a repeating number sequence. Totally random. Happens even without the keypad plugged in. I also tried several keypads so I believe this is an issue with coding

  2. hello i tried following this tutorial but it did not work for me.
    my lcd only displaying squires, and the keypad sims not to respond i have check the wiring over and over but nothing changed. wen i run the code its runs but i keep seeing some numbers.

    some thing like this

    pi@raspberrypi:~/keypad $ sudo python keypadlcdlock.py
    13
    0
    3
    9
    15
    10
    3
    3
    9
    7
    0
    9
    15
    6
    10
    11
    10
    14
    7
    2
    14
    1
    9
    13
    10
    14
    4
    10
    11
    14

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