LCD display (16x2) with I2C backpack in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the library needed to control the LCD with I2C.

Raspberry Pi

import [1]

Drag options to blanks, or click blank then click option'

AI2C_LCD_driver

Blcd_driver

Csmbus

Dlcd_i2c

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to import from smbus

Using smbus directly

Using wrong library names like lcd_driver or lcd_i2c

The I2C_LCD_driver library is used to control the LCD with I2C on Raspberry Pi.

2fill in blank

medium

Complete the code to initialize the LCD display object.

Raspberry Pi

lcd = I2C_LCD_driver.[1]()

Drag options to blanks, or click blank then click option'

ALCD

Blcd

Clcd_init

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase 'LCD' instead of 'lcd'

Trying to call a non-existent function like 'lcd_init'

The lcd function initializes the LCD display object for use.

3fill in blank

hard

Fix the error in the code to display the text 'Hello' on the first line of the LCD.

Raspberry Pi

lcd.[1]('Hello', 1)

Drag options to blanks, or click blank then click option'

Aprint_line

Bdisplay

Clcd_display_string

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using print or print_line which are not valid methods

Using display which is incomplete

The correct method to show text on the LCD is lcd_display_string, where the first argument is the text and the second is the line number.

4fill in blank

hard

Fill both blanks to clear the LCD and then display 'Bye' on the second line.

Raspberry Pi

lcd.[1]()
lcd.[2]('Bye', 2)

Drag options to blanks, or click blank then click option'

Alcd_clear

Blcd_display_string

Cprint

Dreset

Attempts:

3 left

💡 Hint

Common Mistakes

Using reset instead of lcd_clear

Using print instead of lcd_display_string

First, we clear the LCD with lcd_clear(). Then we use lcd_display_string to show 'Bye' on line 2.

5fill in blank

hard

Fill all three blanks to create a function that writes a message on line 1 and clears the display after 3 seconds.

Raspberry Pi

import time

def show_message(msg):
    lcd.[1]()
    lcd.[2](msg, 1)
    time.[3](3)

Drag options to blanks, or click blank then click option'

Alcd_clear

Blcd_display_string

Csleep

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using print instead of lcd_display_string

Using time.print instead of time.sleep

The function clears the LCD with lcd_clear(), displays the message on line 1 with lcd_display_string, then waits 3 seconds using time.sleep(3).

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