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

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output on the OLED for this code?

This code reads a temperature sensor and displays the value on an OLED screen. What will the OLED show?

Raspberry Pi

import board
import adafruit_ssd1306
import digitalio
import time

i2c = board.I2C()
oled = adafruit_ssd1306.SSD1306_I2C(128, 32, i2c)

sensor_value = 25.3

oled.fill(0)
oled.text(f"Temp: {sensor_value} C", 0, 0, 1)
oled.show()

A The OLED displays: Temp: 25.30 C

B The OLED displays: Temp: 25 C

C The OLED displays: Temp: 25.3 C

D The OLED displays nothing (blank screen)

💡 Hint

Look at how the sensor_value is formatted inside the text function.

The f-string inserts the float value 25.3 directly, so the OLED shows exactly 'Temp: 25.3 C'. No rounding or extra decimals are added.

🧠 Conceptual

intermediate

Why do we call oled.show() after oled.text()?

In code that writes text to an OLED screen, why is it necessary to call oled.show() after oled.text()?

A oled.text() writes text to a buffer; oled.show() updates the screen with the buffer content.

B oled.show() clears the screen before oled.text() writes text.

C oled.text() directly updates the screen; oled.show() is optional and does nothing.

D oled.show() turns the OLED on; oled.text() only works if the screen is on.

💡 Hint

Think about how drawing on a screen usually works with buffers.

The oled.text() function writes text to an internal memory buffer. The oled.show() function sends this buffer to the OLED hardware to update the visible display.

🔧 Debug

advanced

Why does this OLED code raise an error?

This code tries to display humidity on the OLED but raises an error. What is the cause?

Raspberry Pi

import board
import adafruit_ssd1306

i2c = board.I2C()
oled = adafruit_ssd1306.SSD1306_I2C(128, 32, i2c)

humidity = 55

oled.fill(0)
oled.text(f"Humidity: {humidity}%", 0, 0, 1)
oled.show()

A No error; code runs and displays 'Humidity: 55%'

B TypeError because humidity is an int, not a string

C RuntimeError because oled.text() does not accept % character

D SyntaxError due to % symbol inside f-string without escaping

💡 Hint

Check how % is used inside f-strings in Python.

The % character inside an f-string is treated as a normal character unless used in formatting expressions. Here it is safe and does not cause errors.

📝 Syntax

advanced

Which option fixes the syntax error in this OLED display code?

This code has a syntax error. Which option fixes it?

Raspberry Pi

import board
import adafruit_ssd1306

i2c = board.I2C()
oled = adafruit_ssd1306.SSD1306_I2C(128, 32, i2c)

sensor = 30

oled.fill(0)
oled.text(f"Value: {sensor", 0, 0, 1)
oled.show()

A oled.text(f"Value: sensor", 0, 0, 1)

B oled.text(f"Value: {sensor}" 0, 0, 1)

C oled.text(f"Value: {sensor})", 0, 0, 1)

D oled.text(f"Value: {sensor}", 0, 0, 1)

💡 Hint

Check the placement of braces and commas inside the f-string.

Option D correctly closes the curly brace and the string, and separates arguments with commas. Others have missing braces, quotes, or commas causing syntax errors.

🚀 Application

expert

How many lines of text can fit on a 128x32 OLED if each line is 8 pixels tall?

You want to display multiple sensor readings on a 128x32 OLED screen. Each text line uses 8 pixels in height. How many lines can you display without overlap?

A 32 lines

B 4 lines

C 8 lines

D 16 lines

💡 Hint

Divide the total height by the height of one line.

The screen height is 32 pixels. Each line is 8 pixels tall. 32 / 8 = 4 lines fit exactly.