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()

# -*- coding: utf-8 -*-
# i2c bus (0 — original Pi, 1 — Rev 2 Pi)
I2CBUS = 1
# LCD Address
ADDRESS = 0x27
import smbus
from time import sleep
class i2c_device:
def __init__(self, addr, port=I2CBUS):
self.addr = addr
self.bus = smbus.SMBus(port)
# Write a single command
def write_cmd(self, cmd):
self.bus.write_byte(self.addr, cmd)
sleep(0.0001)
# Write a command and argument
def write_cmd_arg(self, cmd, data):
self.bus.write_byte_data(self.addr, cmd, data)
sleep(0.0001)
# Write a block of data
def write_block_data(self, cmd, data):
self.bus.write_block_data(self.addr, cmd, data)
sleep(0.0001)
# Read a single byte
def read(self):
return self.bus.read_byte(self.addr)
# Read
def read_data(self, cmd):
return self.bus.read_byte_data(self.addr, cmd)
# Read a block of data
def read_block_data(self, cmd):
return self.bus.read_block_data(self.addr, cmd)
# commands
LCD_CLEARDISPLAY = 0x01
LCD_RETURNHOME = 0x02
LCD_ENTRYMODESET = 0x04
LCD_DISPLAYCONTROL = 0x08
LCD_CURSORSHIFT = 0x10
LCD_FUNCTIONSET = 0x20
LCD_SETCGRAMADDR = 0x40
LCD_SETDDRAMADDR = 0x80
# flags for display entry mode
LCD_ENTRYRIGHT = 0x00
LCD_ENTRYLEFT = 0x02
LCD_ENTRYSHIFTINCREMENT = 0x01
LCD_ENTRYSHIFTDECREMENT = 0x00
# flags for display on/off control
LCD_DISPLAYON = 0x04
LCD_DISPLAYOFF = 0x00
LCD_CURSORON = 0x02
LCD_CURSOROFF = 0x00
LCD_BLINKON = 0x01
LCD_BLINKOFF = 0x00
# flags for display/cursor shift
LCD_DISPLAYMOVE = 0x08
LCD_CURSORMOVE = 0x00
LCD_MOVERIGHT = 0x04
LCD_MOVELEFT = 0x00
# flags for function set
LCD_8BITMODE = 0x10
LCD_4BITMODE = 0x00
LCD_2LINE = 0x08
LCD_1LINE = 0x00
LCD_5x10DOTS = 0x04
LCD_5x8DOTS = 0x00
# flags for backlight control
LCD_BACKLIGHT = 0x08
LCD_NOBACKLIGHT = 0x00
En = 0b00000100 # Enable bit
Rw = 0b00000010 # Read/Write bit
Rs = 0b00000001 # Register select bit
class lcd:
#initializes objects and lcd
def __init__(self):
self.lcd_device = i2c_device(ADDRESS)
self.lcd_write(0x03)
self.lcd_write(0x03)
self.lcd_write(0x03)
self.lcd_write(0x02)
self.lcd_write(LCD_FUNCTIONSET | LCD_2LINE | LCD_5x8DOTS | LCD_4BITMODE)
self.lcd_write(LCD_DISPLAYCONTROL | LCD_DISPLAYON)
self.lcd_write(LCD_CLEARDISPLAY)
self.lcd_write(LCD_ENTRYMODESET | LCD_ENTRYLEFT)
sleep(0.2)
# clocks EN to latch command
def lcd_strobe(self, data):
self.lcd_device.write_cmd(data | En | LCD_BACKLIGHT)
sleep(.0005)
self.lcd_device.write_cmd(((data & ~En) | LCD_BACKLIGHT))
sleep(.0001)
def lcd_write_four_bits(self, data):
self.lcd_device.write_cmd(data | LCD_BACKLIGHT)
self.lcd_strobe(data)
# write a command to lcd
def lcd_write(self, cmd, mode=0):
self.lcd_write_four_bits(mode | (cmd & 0xF0))
self.lcd_write_four_bits(mode | ((cmd << 4) & 0xF0))
# write a character to lcd (or character rom) 0x09: backlight | RS=DR<
# works!
def lcd_write_char(self, charvalue, mode=1):
self.lcd_write_four_bits(mode | (charvalue & 0xF0))
self.lcd_write_four_bits(mode | ((charvalue << 4) & 0xF0))
# put string function with optional char positioning
def lcd_display_string(self, string, line=1, pos=0):
if line == 1:
pos_new = pos
elif line == 2:
pos_new = 0x40 + pos
elif line == 3:
pos_new = 0x14 + pos
elif line == 4:
pos_new = 0x54 + pos
self.lcd_write(0x80 + pos_new)
for char in string:
self.lcd_write(ord(char), Rs)
# clear lcd and set to home
def lcd_clear(self):
self.lcd_write(LCD_CLEARDISPLAY)
self.lcd_write(LCD_RETURNHOME)
# define backlight on/off (lcd.backlight(1); off= lcd.backlight(0)
def backlight(self, state): # for state, 1 = on, 0 = off
if state == 1:
self.lcd_device.write_cmd(LCD_BACKLIGHT)
elif state == 0:
self.lcd_device.write_cmd(LCD_NOBACKLIGHT)
# add custom characters (0 – 7)
def lcd_load_custom_chars(self, fontdata):
self.lcd_write(0x40);
for char in fontdata:
for line in char:
self.lcd_write_char(line)

view raw
I2C_LCD_driver.py
hosted with ❤ by GitHub

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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