LCD display (16x2) with I2C backpack in Raspberry Pi - Mini Project: Build & Apply

LCD Display (16x2) with I2C Backpack on Raspberry Pi

📖 Scenario: You have a Raspberry Pi connected to a 16x2 LCD display with an I2C backpack. You want to show a simple message on the screen using Python.

🎯 Goal: Write a Python program that initializes the LCD display, sets up the I2C address, and prints a welcome message on the first line and a status message on the second line.

📋 What You'll Learn

Create a variable called lcd_address with the I2C address 0x27.

Create an instance of the LCD display using the lcd_address and 16 columns and 2 rows.

Write the message 'Hello, Raspberry Pi!' on the first line of the LCD.

Write the message 'I2C LCD Ready' on the second line of the LCD.

💡 Why This Matters

🌍 Real World

Many Raspberry Pi projects use 16x2 LCDs with I2C backpacks to show status, sensor readings, or user prompts in a compact way.

💼 Career

Understanding how to interface hardware components like LCDs with Raspberry Pi is useful for embedded systems, IoT development, and prototyping physical computing projects.

1

Set up the LCD display library and I2C address

Import the I2C_LCD_driver module and create a variable called lcd_address with the value 0x27.

Raspberry Pi

# Import the LCD driver and set the I2C address
# Your code here

Hint

The I2C address for many LCD backpacks is 0x27. You need to import the driver module first.

2

Create the LCD display instance

Create a variable called lcd by calling I2C_LCD_driver.lcd() with lcd_address, cols=16, and rows=2.

Raspberry Pi

import I2C_LCD_driver
lcd_address = 0x27
# Create the lcd instance with 16 columns and 2 rows
# Your code here

Hint

Use the lcd class from the driver with the correct address and size.

3

Write messages to the LCD display

Use lcd.lcd_display_string() to write 'Hello, Raspberry Pi!' on line 1 and 'I2C LCD Ready' on line 2.

Raspberry Pi

import I2C_LCD_driver
lcd_address = 0x27
lcd = I2C_LCD_driver.lcd(address=lcd_address, cols=16, rows=2)
# Display 'Hello, Raspberry Pi!' on line 1
# Display 'I2C LCD Ready' on line 2
# Your code here

Hint

Use the lcd_display_string method with the message and the line number.

4

Print confirmation message to console

Write a print() statement that outputs 'LCD messages sent successfully.' to confirm the program ran.

Raspberry Pi

import I2C_LCD_driver
lcd_address = 0x27
lcd = I2C_LCD_driver.lcd(address=lcd_address, cols=16, rows=2)
lcd.lcd_display_string('Hello, Raspberry Pi!', 1)
lcd.lcd_display_string('I2C LCD Ready', 2)
# Print confirmation message
# Your code here

Hint

Use print() to show a message on the console.

Practice

1. What is the main advantage of using an I2C backpack with a 16x2 LCD on a Raspberry Pi?

easy

A. It powers the Raspberry Pi without an external source

B. It reduces the number of GPIO pins needed to control the LCD

C. It allows the LCD to display colors

D. It increases the LCD resolution beyond 16x2

Solution

1. Step 1: Understand I2C backpack purpose

   The I2C backpack simplifies wiring by using only two data lines (SDA and SCL) instead of many GPIO pins.

2. Step 2: Compare options

   Options A, B, and C are unrelated to I2C backpacks; only It reduces the number of GPIO pins needed to control the LCD correctly states the advantage.

3. Final Answer:

   It reduces the number of GPIO pins needed to control the LCD -> Option B

4. Quick Check:

   I2C reduces wiring = D [OK]

Hint: I2C means fewer wires needed for LCD control [OK]

Common Mistakes:

• Thinking I2C changes LCD resolution
• Assuming I2C adds color support
• Confusing power supply with data interface

2. Which Python library is commonly used to control a 16x2 LCD with an I2C backpack on Raspberry Pi?

easy

A. NumPy

B. PIL

C. RPLCD

D. Matplotlib

Solution

1. Step 1: Identify libraries purpose

   RPLCD is designed for controlling LCD displays, including those with I2C backpacks.

2. Step 2: Eliminate unrelated libraries

   PIL is for images, NumPy for math arrays, Matplotlib for plotting; none control LCDs.

3. Final Answer:

   RPLCD -> Option C

4. Quick Check:

   LCD control library = RPLCD [OK]

Hint: RPLCD is the go-to library for LCDs on Raspberry Pi [OK]

Common Mistakes:

• Confusing image or math libraries with LCD control
• Using libraries without I2C support
• Misspelling library names

3. What will be the output on the LCD after running this Python code snippet?

from RPLCD.i2c import CharLCD
lcd = CharLCD('PCF8574', 0x27)
lcd.write_string('Hello\nWorld!')

medium

A. Hello on first line, World! on second line

B. HelloWorld! on first line only

C. SyntaxError due to newline character

D. Nothing displayed because address is wrong

Solution

1. Step 1: Understand write_string with newline

   The '\n' moves the cursor to the second line on the LCD.

2. Step 2: Check address and syntax

   Address 0x27 is a common default; no syntax error in code.

3. Final Answer:

   Hello on first line, World! on second line -> Option A

4. Quick Check:

   Newline moves text to line 2 = C [OK]

Hint: Use '\n' to move to second line on LCD [OK]

Common Mistakes:

• Thinking '\n' causes syntax error
• Assuming text stays on one line
• Using wrong I2C address without checking

4. Identify the error in this code snippet for initializing the LCD with I2C backpack:

from RPLCD.i2c import CharLCD
lcd = CharLCD(i2c_expander='PCF8574', address=0x3F)
lcd.write_string('Test')

medium

A. Missing 'port' parameter for CharLCD initialization

B. The parameter name should be 'address' not 'i2c_expander'

C. The I2C address 0x3F is invalid for this device

D. The parameter 'i2c_expander' should be 'i2c_expander' but is correct here

Solution

1. Step 1: Check CharLCD parameters

   CharLCD requires 'i2c_expander', 'address', and 'port' parameters for I2C setup.

2. Step 2: Identify missing parameter

   The code misses the 'port' parameter, which is needed to specify the I2C bus number.

3. Final Answer:

   Missing 'port' parameter for CharLCD initialization -> Option A

4. Quick Check:

   Missing required 'port' parameter = A [OK]

Hint: Always include 'port' when initializing CharLCD with I2C [OK]

Common Mistakes:

• Assuming address 0x3F is always wrong
• Confusing parameter names
• Omitting required parameters

5. You want to display a scrolling message on a 16x2 LCD with I2C backpack using Python. Which approach is best?

hard

A. Write the full message once and rely on LCD auto-scroll

B. Change the I2C address dynamically during scrolling

C. Clear the LCD and write the full message repeatedly without delay

D. Use a loop to write substrings shifting one character at a time with delays

Solution

1. Step 1: Understand scrolling on 16x2 LCD

   The LCD does not auto-scroll long messages; you must manually shift text.

2. Step 2: Choose method to scroll

   Using a loop to write substrings with delays simulates scrolling smoothly.

3. Step 3: Eliminate wrong options

   Write the full message once and rely on LCD auto-scroll is incorrect because LCD won't auto-scroll; C causes flicker; D is unrelated.

4. Final Answer:

   Use a loop to write substrings shifting one character at a time with delays -> Option D

5. Quick Check:

   Manual substring loop scrolls text = B [OK]

Hint: Scroll by shifting substrings in a timed loop [OK]

Common Mistakes:

• Expecting LCD to auto-scroll long text
• Clearing display too often causing flicker
• Trying to change I2C address during scrolling