Raspberry Pi Pico -- 16x2 LCD, 4Bit Mode Interface, BCD Counter

This experimentation is about interfacing 16X2 LCD with Raspberry Pi Pico, and using Python for programming the LCD

Visit the "VESZLE - The Art Of Electronics" you tube channel for further information and videos.

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1602 LCD 4Bit mode video link

The Raspberry Pi Pico is a tiny, fast, and versatile board built using RP2040 features a dual-core Arm Cortex-M0+ processor with 264KB internal RAM and support for up to 16MB of off-chip Flash. It provides wide range of flexible I/O options includes I2C, SPI, and uniquely Programmable I/O (GPIO) pins.

In Embedded system design, character LCD display [16x2, 16x4, 20x2 or 20x4 LCDs] is used for display the system status, menu navigation and configuring system parameters. This experimentation is about interfacing 16X2 LCD with Raspberry Pi Pico, and using Python for programming the LCD.

“Raspberry Pi Pico, Getting Started on Board Blink LED” Instruct-able / You-tube by PugazhM

The “lcd_4bit_mode.py” driver library

Raspberry Pi Pico

Micro USB Cable

16x2 LCD Keypad Shield

The 16x2 is very common type LCD, with two rows.

Each row displays 16 characters of either 5x7 or 5x8 dot matrix characters. Totally 32 alpha numerical charters can be displayed in two rows.

It has inbuilt font ROM, for decoding the ASCII input.

There's a dot pitch between two characters and a space between lines, thus separating characters and lines.

The 16x2 LCD supports 8-bit interface mode or 4-bit interface mode.

This experiment uses 4-bit interface mode.

The generally available Arduino shield of “16x2 LCD Keypad shield”, can be directly connected into Arduino Uno board. It consists of inbuild LCD brightness control circuit and 5 Keys. The keys are interconnected with potential divider network and when pressed, it provides divided potential on an analog pin.

The “16x2 LCD Keypad shield” can be connected to Raspberry Pi Pico GPIO pins (GPIO0--GPIO6). LCD operates at 4-bit data mode as given in above circuit.

If the display is not visible, adjust the Contrast pot (1K), to make it visible.

The above table describes the 16x2 LCD -- Shield – RPi Pico pin connections

Following LCD functionalities are provided by the “lcd_4bit_mode.py” python library.

Reset

WriteCommand

WriteData

BackLightOn

BackLighOff

CursorOn

CursorOff

CursorBlink

ClearScreenCursorHome

WriteLine

Download “lcd_4bit_mode.py” driver library.

Open the RPi Pico as drive, and then copy the library into root directory.

'''
 Licence: GPLv3
 Copyright 2021 Muthuswamy Pugazhendi 
 Name:- M.Pugazhendi
 Date:-  12thJul2021
 Version:- V0.1
 e-mail:- muthuswamy.pugazhendi@gmail.com
'''
import utime

class LCD16x2:
    
    def __init__(self, RS, ENABLE, BACK_LIGHT, D4, D5, D6, D7):
        self.RS = RS
        self.ENABLE = ENABLE
        self.BACK_LIGHT = BACK_LIGHT
        self.D4 = D4
        self.D5 = D5
        self.D6 = D6
        self.D7 = D7
        self.Reset()
    
    def Reset(self):
        self.RS.value(0)
        self.WriteCommand(0x03)
        self.WriteCommand(0x03)
        self.WriteCommand(0x03)
        
        #Initialize LCD into 4 bit mode
        self.WriteCommand(0x02)
        
        #Enable 5x7 character mode
        self.WriteCommand(0x28)
        
        #Cursor off
        self.WriteCommand(0x0C)
        
        #Increment cursor
        self.WriteCommand(0x06)
        
        #Clear screen
        self.WriteCommand(0x01)
        
        #Sleep for two mSeconds
        utime.sleep_ms(2)
     
    # Generate EnablePulse
    def EnablePulse(self):
        self.ENABLE.value(1)
        utime.sleep_us(40)
        self.ENABLE.value(0)
        utime.sleep_us(40)

    # Write a byte to LCD
    # Separate into 2 nibbles and then write to LCD
    def WriteByte(self, data):
       self.D4.value((data & 0b00010000) >>4)
       self.D5.value((data & 0b00100000) >>5)
       self.D6.value((data & 0b01000000) >>6)
       self.D7.value((data & 0b10000000) >>7)
       self.EnablePulse()
       
       self.D4.value((data & 0b00000001) >>0)
       self.D5.value((data & 0b00000010) >>1)
       self.D6.value((data & 0b00000100) >>2)
       self.D7.value((data & 0b00001000) >>3)
       self.EnablePulse()
       
    # Write a command to LCD
    def WriteCommand(self, data):
        # Disable Register Select
        self.RS.value(0)
        # Write Command Byte to LCD
        self.WriteByte(data)
        
    # Write a data to LCD
    def WriteData(self, data):
        # Enable Register Select
        self.RS.value(1)
        # Write Command Byte to LCD
        self.WriteByte(data)
        # Disable Register Select
        self.RS.value(0)
    
    # Writes a string into Line 1 or Line2
    def WriteLine(self, string, line_number):
        if(line_number == 1):
            self.WriteCommand(0x80)
            for x in string:
                self.WriteData(ord(x))
        if(line_number == 2):
            self.WriteCommand(0xC0)
            for x in string:
                self.WriteData(ord(x))    
    # Clear Screen
    def ClearScreenCursorHome(self):
        self.WriteCommand(0x01)
        self.WriteCommand(0x02)
        # Clear screen and put the cursor into Home needs longer time
        # Introduce two mSeconds delay
        utime.sleep_ms(2)
        
    # Back light On
    def BackLightOn(self):
        self.BACK_LIGHT.value(1)
        
    # Back light Off
    def BackLightOff(self):
        self.BACK_LIGHT.value(0)
        
    # Cursor On
    def CursorOn(self):
        self.WriteCommand(0x0E)

    # Cursor Blinking
    def CursorBlink(self):
        self.WriteCommand(0x0D)
        
    # Cursor Off
    def CursorOff(self):
        self.WriteCommand(0x0C)

LCD is initialized and welcome screen of “Raspberry Pi Pico 16x2 LCD” is displayed in two rows, for about 5 seconds.

The count variable is initialized with 250, and added by one count, at every 2 Seconds interval.

Updated count variable, is displayed on the LCD “UP COUNTER” at line one counts at line two.

'''
 Demonstrates the use of 1602 LCD Keypad shield with RPi Pico.
 
 * 16x2 LCD Connection diagram
 * LCD 4 bit mode interface
 * Displaying welcome screen
 * Clear Display, Cursor on, Cursor Off, Backlight On, Back light Off
 * Write Command, Write data functionalities
  
 * The Raspberry Pi Pico pin connections for 16x2 LCD Keypad shield are given below:
 
 # LCD Power Pins
 * 16x2 LCD VCC pin to VBUS
 * 16x2 LCD GND pin to GND
 
 # LCD Data Pins
 * 16x2 LCD D4 pin to GPIO0
 * 16x2 LCD D5 pin to GPIO1
 * 16x2 LCD D6 pin to GPIO2
 * 16x2 LCD D7 pin to GPIO3
 
 # LCD Control Pins
 * 16x2 LCD RS pin to GPIO4
 * 16x2 LCD ENABLE pin to GPIO5
 * 16x2 LCD BACK LIGHT pin to GPIO6
 
 # Caution do not connect A0 pin of shield to RPi Pico.
 # Potential divided key connections, provides +5VDC output.
  
 Name:- M.Pugazhendi
 Date:-  13thJul2021
 Version:- V0.1
 e-mail:- muthuswamy.pugazhendi@gmail.com
'''

import machine

# Import lcd_4bit_mode
import lcd_4bit_mode

# Import time
import time

# Initialize LCD pins

RS = machine.Pin(4,machine.Pin.OUT)
ENABLE = machine.Pin(5,machine.Pin.OUT)
BACK_LIGHT = machine.Pin(6,machine.Pin.OUT)
D4 = machine.Pin(0,machine.Pin.OUT)
D5 = machine.Pin(1,machine.Pin.OUT)
D6 = machine.Pin(2,machine.Pin.OUT)
D7 = machine.Pin(3,machine.Pin.OUT)

display = lcd_4bit_mode.LCD16x2(RS,ENABLE,BACK_LIGHT,D4,D5,D6,D7)

display.BackLightOn()

# Line one string
display.WriteLine('Raspberry Pi',1)

# Line two string
display.WriteLine('Pico 16x2 LCD',2)
time.sleep(5)

count = 250
while True:
    # Clear Screen
    display.ClearScreenCursorHome()
    
    #Count up
    count = count + 1
    
    #Write into LCD
    display.WriteLine('   UP COUNTER',1)
    display.WriteLine('       ' + str(count),2)
    
    #Wair for two seconds
    time.sleep(2)

The project is successfully completed with Raspberry Pi Pico and 1602 LCD Keypad shield

The 16x2 LCD can be used for many embedded projects as alpha numerical display.

Result_Video.mp4

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1602 LCD 4Bit mode video link