OLED display with I2C (SSD1306) in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output on the OLED display?

Given the following Python code snippet for an SSD1306 OLED display connected via I2C on a Raspberry Pi, what text will appear on the screen?

Raspberry Pi

from PIL import Image, ImageDraw, ImageFont
import board
import busio
import adafruit_ssd1306

i2c = busio.I2C(board.SCL, board.SDA)
display = adafruit_ssd1306.SSD1306_I2C(128, 32, i2c)
display.fill(0)
display.show()

image = Image.new('1', (display.width, display.height))
draw = ImageDraw.Draw(image)

font = ImageFont.load_default()
draw.text((0, 0), 'Hello, Pi!', font=font, fill=255)
display.image(image)
display.show()

A The OLED shows the text 'Hello, Pi!' at the top-left corner

B The OLED shows the text 'Hello, Pi!' centered on the screen

C The OLED remains blank with no text displayed

D The OLED shows an error message about I2C communication

💡 Hint

Look at the coordinates used in draw.text and the display size.

The text is drawn at position (0, 0), which is the top-left corner of the display. The display size is 128x32 pixels, so the text appears there. The code clears the display first, then draws the text and updates the screen.

🧠 Conceptual

intermediate

Why is the display.fill(0) method called before drawing?

In the SSD1306 OLED display code, what is the purpose of calling display.fill(0) before drawing new content?

A It clears the display by turning all pixels off

B It sets the brightness of the display to zero

C It initializes the I2C communication bus

D It saves the current display content to memory

💡 Hint

Think about what 'fill(0)' might mean for a pixel-based screen.

Calling display.fill(0) turns off all pixels, effectively clearing the screen before drawing new content. This prevents old images or text from overlapping.

🔧 Debug

advanced

Identify the error causing the display to remain blank

This code is intended to display 'Test' on the OLED, but the screen stays blank. What is the cause?

Raspberry Pi

from PIL import Image, ImageDraw, ImageFont
import board
import busio
import adafruit_ssd1306

i2c = busio.I2C(board.SCL, board.SDA)
display = adafruit_ssd1306.SSD1306_I2C(128, 64, i2c)
display.fill(0)
display.show()

image = Image.new('1', (display.width, display.height))
draw = ImageDraw.Draw(image)

font = ImageFont.load_default()
draw.text((0, 0), 'Test', font=font, fill=255)
# Missing display.image(image) here
display.show()

A The font is not loaded correctly, causing no text to render

B The display size 128x64 is not supported by the OLED

C The I2C bus is not initialized properly

D The display.image(image) call is missing before display.show()

💡 Hint

Check if the image is sent to the display before calling show().

The image with the drawn text must be sent to the display buffer using display.image(image) before calling display.show(). Without this, the display shows the previous or blank content.

📝 Syntax

advanced

Which code snippet correctly initializes the SSD1306 display?

Choose the correct Python code to initialize a 128x32 SSD1306 OLED display over I2C on a Raspberry Pi.

A

i2c = busio.I2C(board.SCL, board.SDA)
display = adafruit_ssd1306.SSD1306_SPI(128, 32, i2c)

B

i2c = busio.I2C(board.SDA, board.SCL)
display = adafruit_ssd1306.SSD1306_I2C(32, 128, i2c)

C

i2c = busio.I2C(board.SCL, board.SDA)
display = adafruit_ssd1306.SSD1306_I2C(128, 32, i2c)

D

i2c = busio.I2C(board.SCL, board.SDA)
display = adafruit_ssd1306.SSD1306_I2C(128, 64, i2c)

💡 Hint

Check the order of pins and display dimensions.

Option C correctly uses board.SCL and board.SDA in the right order and specifies the correct display size 128x32 for this OLED. Option C swaps pins and dimensions incorrectly. Option C uses SPI class instead of I2C. Option C uses wrong display height.

🚀 Application

expert

How many pixels are lit after this drawing code runs?

Consider this code drawing a white rectangle on a 128x32 SSD1306 OLED display. How many pixels are lit (set to 1) after running?

Raspberry Pi

from PIL import Image, ImageDraw
import board
import busio
import adafruit_ssd1306

i2c = busio.I2C(board.SCL, board.SDA)
display = adafruit_ssd1306.SSD1306_I2C(128, 32, i2c)
display.fill(0)
display.show()

image = Image.new('1', (display.width, display.height))
draw = ImageDraw.Draw(image)

draw.rectangle((10, 5, 20, 15), outline=255, fill=255)
display.image(image)
display.show()

A 110 pixels

B 121 pixels

C 100 pixels

D 1210 pixels

💡 Hint

Calculate width and height of the rectangle and multiply.

The rectangle covers from x=10 to 20 (inclusive) and y=5 to 15 (inclusive). Width = 20 - 10 + 1 = 11 pixels, height = 15 - 5 + 1 = 11 pixels. Total pixels lit = 11 * 11 = 121.