Displaying text on OLED in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output on the OLED?

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

Raspberry Pi

from PIL import Image, ImageDraw, ImageFont
import Adafruit_SSD1306

# Initialize display
disp = Adafruit_SSD1306.SSD1306_128_64(rst=None)
disp.begin()
disp.clear()
disp.display()

# Create blank image for drawing
width = disp.width
height = disp.height
image = Image.new('1', (width, height))
draw = ImageDraw.Draw(image)

# Load default font
font = ImageFont.load_default()

# Draw text
draw.text((0, 0), 'Hello, Pi!', font=font, fill=255)

# Display image
disp.image(image)
disp.display()

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

B The OLED displays an error message because the font is not loaded.

C The OLED displays nothing because the display was not cleared.

D The OLED displays the text 'Hello, Pi!' centered on the screen.

💡 Hint

Look at the coordinates used in draw.text and the font loading method.

The text 'Hello, Pi!' is drawn at coordinates (0, 0) using the default font, so it appears at the top-left corner. The display is cleared before drawing, so the text is visible.

🧠 Conceptual

intermediate

Why do we call disp.display() after drawing?

In Raspberry Pi OLED programming, why is it necessary to call disp.display() after drawing on the image?

A Because disp.display() sends the drawn image buffer to the OLED hardware to update the screen.

B Because disp.display() clears the screen before drawing new content.

C Because disp.display() loads the font used for drawing text.

D Because disp.display() initializes the OLED display hardware.

💡 Hint

Think about what happens after you draw on an image but before you see it on the screen.

Drawing commands modify an image buffer in memory. Calling disp.display() sends this buffer to the OLED hardware so the changes appear on the screen.

🔧 Debug

advanced

Why does this OLED text not show?

This code runs without errors but the OLED screen stays blank. What is the problem?

Raspberry Pi

from PIL import Image, ImageDraw, ImageFont
import Adafruit_SSD1306

disp = Adafruit_SSD1306.SSD1306_128_64(rst=None)
disp.begin()

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

font = ImageFont.load_default()

draw.text((10, 10), 'Test', font=font, fill=255)

# Missing disp.image(image) call
# Missing disp.display() call

A The display is not initialized with disp.begin(), causing no output.

B The font is not loaded correctly, so text cannot be drawn.

C The image mode '1' is incorrect; it should be 'RGB'.

D The code does not call disp.image(image) and disp.display(), so the image is never sent to the OLED.

💡 Hint

Check if the image is sent to the display after drawing.

Drawing on the image alone does not update the OLED. You must call disp.image(image) to set the buffer and disp.display() to refresh the screen.

📝 Syntax

advanced

Identify the syntax error in this OLED text code

Which option contains the correct syntax to draw text on the OLED using PIL and Adafruit_SSD1306?

Raspberry Pi

draw.text((0, 0), 'Hello World', font=font, fill=255)

A draw.text((0, 0), 'Hello World', font=font fill=255)

B draw.text[0, 0]('Hello World', font=font, fill=255)

C draw.text((0, 0), 'Hello World', font=font, fill=255)

D draw.text((0, 0), 'Hello World', font=font, fill='255')

💡 Hint

Check the function call syntax and parameter separators.

Option C uses correct function call syntax with parentheses and commas. Option C uses brackets incorrectly. Option C misses a comma. Option C uses fill as a string instead of an integer.

🚀 Application

expert

How many characters fit on a 128x64 OLED with default font?

Using the default PIL font (approximately 6 pixels wide and 8 pixels tall per character), how many characters can fit on a 128x64 OLED screen in a single line?

A 64 characters

B 21 characters

C 16 characters

D 32 characters

💡 Hint

Divide the screen width by the character width to find how many fit horizontally.

128 pixels width divided by 6 pixels per character equals about 21 characters per line. However, the default font is actually 6 pixels wide including spacing, so 21 is correct. But since 6*21=126, 21 fits. Option B says 32 which is too many. So correct answer is A.