Displaying sensor readings on OLED in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the library needed to control the OLED display.

Raspberry Pi

import [1]

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

Aboard

Btime

Cadafruit_ssd1306

Drandom

Attempts:

3 left

💡 Hint

Common Mistakes

Importing 'board' instead of the OLED library.

Importing 'time' or 'random' which are unrelated here.

The adafruit_ssd1306 library is used to control the OLED display on Raspberry Pi.

2fill in blank

medium

Complete the code to initialize the I2C interface for the OLED display.

Raspberry Pi

i2c = [1]()

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

ASPI

BI2C

CUART

DGPIO

Attempts:

3 left

💡 Hint

Common Mistakes

Using SPI or UART which are different communication protocols.

Using GPIO which is general purpose pins, not a bus.

The OLED display uses the I2C communication protocol, so we initialize it with I2C().

3fill in blank

hard

Fix the error in the code to create the OLED display object with correct width and height.

Raspberry Pi

display = adafruit_ssd1306.SSD1306_I2C([1], 64, i2c)

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

A128

B32

C16

D256

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping width and height values.

Using incorrect pixel dimensions.

The OLED display used here has a width of 128 pixels and a height of 64 pixels. The first argument is the width, so it should be 128. The code has 64 as the second argument (height), so the first argument must be 128.

4fill in blank

hard

Fill both blanks to clear the display and then show the new content.

Raspberry Pi

display.[1]()
display.[2]()

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

Afill

Bshow

Cclear

Dupdate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'clear' instead of 'fill' to empty the display.

Using 'update' instead of 'show' to refresh the display.

To clear the display, we use fill(). To update the display with new content, we use show().

5fill in blank

hard

Fill both blanks to create a dictionary comprehension that stores sensor readings greater than 50.

Raspberry Pi

filtered_readings = {sensor: value for sensor, value in readings.items() if value {BLANK_1}} {{BLANK_2}}
print(filtered_readings)

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

A>

B50

C)

D]

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' in the condition.

Forgetting to close the print statement with a parenthesis.

The dictionary comprehension filters readings where the value is greater than 50. The print statement ends with a closing parenthesis ).

Practice

1. What is the main purpose of using an OLED screen with a Raspberry Pi when working with sensors?

easy

A. To increase the sensor's accuracy

B. To store sensor data permanently

C. To display sensor readings clearly and in real-time

D. To power the sensors automatically

Solution

1. Step 1: Understand OLED screen function

   OLED screens are used to show information visually, such as text or images.

2. Step 2: Relate to sensor data usage

   Displaying sensor readings on OLED helps users see live data clearly and quickly.

3. Final Answer:

   To display sensor readings clearly and in real-time -> Option C

4. Quick Check:

   OLED shows sensor data live = A [OK]

Hint: OLED screens show live sensor data visually [OK]

Common Mistakes:

• Thinking OLED stores data permanently
• Confusing display with sensor accuracy
• Assuming OLED powers sensors

2. Which Python library is commonly used to control an SSD1306 OLED display on a Raspberry Pi?

easy

A. Adafruit_SSD1306

B. matplotlib

C. pygame

D. numpy

Solution

1. Step 1: Identify libraries for OLED control

   Adafruit_SSD1306 is a popular Python library designed to control SSD1306 OLED displays.

2. Step 2: Exclude unrelated libraries

   matplotlib and pygame are for graphics but not specific to OLED control; numpy is for math operations.

3. Final Answer:

   Adafruit_SSD1306 -> Option A

4. Quick Check:

   Use Adafruit_SSD1306 for SSD1306 OLED [OK]

Hint: Use Adafruit_SSD1306 library for SSD1306 OLED screens [OK]

Common Mistakes:

• Choosing matplotlib which is for plotting graphs
• Selecting pygame meant for game development
• Picking numpy which is for numerical calculations

3. What will be the output on the OLED if the following Python code runs successfully?

import Adafruit_SSD1306
from PIL import Image, ImageDraw, ImageFont

# 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)

# Draw text
font = ImageFont.load_default()
draw.text((0, 0), 'Temp: 25C', font=font, fill=255)

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

medium

A. The OLED will show a white screen with no text

B. The OLED will remain blank

C. The code will cause a syntax error

D. The OLED will show the text 'Temp: 25C' at the top-left corner

Solution

1. Step 1: Analyze text drawing commands

   The code draws 'Temp: 25C' at position (0,0) using a default font on a blank image.

2. Step 2: Understand display update

   Calling disp.image(image) and disp.display() sends the image to the OLED, showing the text.

3. Final Answer:

   The OLED will show the text 'Temp: 25C' at the top-left corner -> Option D

4. Quick Check:

   Text drawn and displayed = A [OK]

Hint: Text drawn at (0,0) appears top-left on OLED [OK]

Common Mistakes:

• Assuming display stays blank without disp.display()
• Confusing image creation with display output
• Thinking code has syntax errors

4. Identify the error in this code snippet meant to update an OLED with sensor data:

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

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

sensor_value = 30

draw.text((0, 0), f'Temp: {sensor_value}C', font=font, fill=255)

# Missing disp.image(image) here

disp.display()

medium

A. Missing disp.image(image) before disp.display()

B. Incorrect font loading method

C. Image size does not match display size

D. disp.clear() should be called after disp.display()

Solution

1. Step 1: Check display update sequence

   To update OLED, image must be sent with disp.image(image) before disp.display().

2. Step 2: Identify missing command

   The code misses disp.image(image), so display shows old or blank content.

3. Final Answer:

   Missing disp.image(image) before disp.display() -> Option A

4. Quick Check:

   disp.image(image) needed before disp.display() [OK]

Hint: Always call disp.image(image) before disp.display() [OK]

Common Mistakes:

• Forgetting to send image to display
• Calling disp.clear() too late
• Using wrong font loading method

5. You want to continuously display live temperature readings from a sensor on an OLED screen using Python. Which approach correctly updates the display every second without flickering?

import time
while True:
    temp = read_sensor()
    image = Image.new('1', (disp.width, disp.height))
    draw = ImageDraw.Draw(image)
    draw.text((0, 0), f'Temp: {temp}C', font=font, fill=255)
    disp.image(image)
    disp.display()
    time.sleep(1)

What is the best improvement to reduce flicker?

hard

A. Clear the display before drawing each new image

B. Create the image and draw objects once outside the loop and reuse them

C. Remove time.sleep(1) to update faster

D. Use disp.clear() after disp.display() inside the loop

Solution

1. Step 1: Understand flicker cause

   Creating new image and draw objects each loop causes flicker due to redraw overhead.

2. Step 2: Optimize by reusing objects

   Creating image and draw once outside loop and clearing draw area inside loop reduces flicker.

3. Final Answer:

   Create the image and draw objects once outside the loop and reuse them -> Option B

4. Quick Check:

   Reuse image/draw objects to reduce flicker [OK]

Hint: Create image/draw once outside loop to avoid flicker [OK]

Common Mistakes:

• Recreating image each loop causing flicker
• Removing sleep causing too fast updates
• Calling disp.clear() after display has no effect