Displaying text on OLED in Raspberry Pi

Introduction

We use OLED displays to show information like text or numbers in a small, clear way. Displaying text on an OLED helps us see messages directly on the device.

You want to show sensor readings like temperature or humidity on a small screen.

You need to display status messages or alerts on a device without a full monitor.

You want to create a simple user interface on a Raspberry Pi project.

You want to show time or date on a compact display.

You want to debug or check values without connecting to a computer.

Syntax

Raspberry Pi

from luma.core.interface.serial import i2c
from luma.oled.device import sh1106
from PIL import ImageDraw, ImageFont

serial = i2c(port=1, address=0x3C)
device = sh1106(serial)

with canvas(device) as draw:
    draw.text((x, y), "Your text here", fill="white", font=font)

Use the canvas context to draw on the OLED safely.

Coordinates (x, y) start at the top-left corner of the screen.

Examples

This example shows how to write 'Hello OLED' at position (10, 10) on the screen.

Raspberry Pi

from luma.core.interface.serial import i2c
from luma.oled.device import sh1106
from luma.core.render import canvas

serial = i2c(port=1, address=0x3C)
device = sh1106(serial)

with canvas(device) as draw:
    draw.text((10, 10), "Hello OLED", fill="white")

This example uses a default font to display temperature at the top-left corner.

Raspberry Pi

from luma.core.interface.serial import i2c
from luma.oled.device import sh1106
from luma.core.render import canvas
from PIL import ImageFont

serial = i2c(port=1, address=0x3C)
device = sh1106(serial)
font = ImageFont.load_default()

with canvas(device) as draw:
    draw.text((0, 0), "Temp: 25C", fill="white", font=font)

Sample Program

This program connects to the OLED screen and shows two lines of text at different positions.

Raspberry Pi

from luma.core.interface.serial import i2c
from luma.oled.device import sh1106
from luma.core.render import canvas
from PIL import ImageFont

# Setup I2C and OLED device
serial = i2c(port=1, address=0x3C)
device = sh1106(serial)

# Load default font
font = ImageFont.load_default()

# Display text on OLED
with canvas(device) as draw:
    draw.text((5, 5), "Hello, Raspberry Pi!", fill="white", font=font)
    draw.text((5, 20), "OLED Display Test", fill="white", font=font)

Important Notes

Make sure your OLED is connected correctly to the Raspberry Pi's I2C pins.

Use ImageFont.load_default() for simple text or load custom fonts for style.

Always use the canvas context to update the display to avoid flickering.

Summary

OLED displays show text by drawing on a small screen using coordinates.

Use the canvas context to safely draw text on the OLED.

Connect the OLED via I2C and use libraries like luma.oled to control it easily.

Practice

1. What is the main purpose of using the canvas context when displaying text on an OLED with Raspberry Pi?

easy

A. To draw and update text or graphics on the OLED screen

B. To connect the Raspberry Pi to the internet

C. To install the OLED driver software

D. To power the OLED screen

Solution

1. Step 1: Understand the role of canvas in OLED display

   The canvas context is used to draw graphics or text before showing it on the OLED screen.

2. Step 2: Connect canvas to display update

   Drawing on the canvas allows you to prepare the image or text, which then updates the OLED display when done.

3. Final Answer:

   To draw and update text or graphics on the OLED screen -> Option A

4. Quick Check:

   Canvas draws text/graphics = A [OK]

Hint: Canvas is where you draw before showing on OLED [OK]

Common Mistakes:

• Thinking canvas connects to internet
• Confusing canvas with hardware power
• Assuming canvas installs drivers

2. Which of the following is the correct way to import the OLED device class from the luma.oled.device module in Python?

easy

A. import ssd1306 from luma.oled.device

B. import luma.oled.device.ssd1306

C. from luma.oled import device.ssd1306

D. from luma.oled.device import ssd1306

Solution

1. Step 1: Recall Python import syntax

   Correct import uses 'from module import class' format.

2. Step 2: Match correct module and class names

   The device class for OLED is 'ssd1306' inside 'luma.oled.device'. So 'from luma.oled.device import ssd1306' is correct.

3. Final Answer:

   from luma.oled.device import ssd1306 -> Option D

4. Quick Check:

   Correct Python import = A [OK]

Hint: Use 'from module import class' for specific imports [OK]

Common Mistakes:

• Using dot notation inside import incorrectly
• Trying to import with 'import class from module'
• Importing whole module instead of class

3. What will be the output on the OLED screen after running this code snippet?

from luma.core.interface.serial import i2c
from luma.oled.device import ssd1306
from luma.core.render import canvas

serial = i2c(port=1, address=0x3C)
device = ssd1306(serial)

with canvas(device) as draw:
    draw.text((10, 10), "Hi OLED", fill="white")

medium

A. The text appears but in black color, invisible on screen

B. The screen stays blank with no text

C. The text 'Hi OLED' appears at position (10, 10) in white color

D. An error occurs because 'canvas' is not imported

Solution

1. Step 1: Analyze the code setup

   The code initializes the OLED device and opens a canvas context to draw text at (10, 10) with white color.

2. Step 2: Understand canvas drawing effect

   Text 'Hi OLED' is drawn on the canvas and shown on the OLED screen at the specified position.

3. Final Answer:

   The text 'Hi OLED' appears at position (10, 10) in white color -> Option C

4. Quick Check:

   Text 'Hi OLED' at (10,10) white = D [OK]

Hint: Text inside canvas with fill='white' shows on OLED [OK]

Common Mistakes:

• Forgetting to use 'with canvas' context
• Using wrong fill color making text invisible
• Not initializing device before drawing

4. Identify the error in this code that tries to display 'Hello' on the OLED:

from luma.oled.device import ssd1306
from luma.core.render import canvas

device = ssd1306()

with canvas(device) as draw:
    draw.text((0, 0), "Hello", fill=1)

medium

A. Canvas context is not used properly

B. Missing serial interface initialization for ssd1306 device

C. Incorrect fill color value; should be a string

D. Text coordinates (0, 0) are invalid

Solution

1. Step 1: Check device initialization

   The ssd1306 device requires a serial interface (like i2c) passed during initialization, which is missing here.

2. Step 2: Verify other parts

   Fill value '1' is valid for monochrome, canvas usage is correct, and (0,0) is valid coordinate.

3. Final Answer:

   Missing serial interface initialization for ssd1306 device -> Option B

4. Quick Check:

   Device needs serial interface = C [OK]

Hint: Always initialize ssd1306 with serial interface first [OK]

Common Mistakes:

• Not passing serial interface to device
• Confusing fill color types
• Misusing canvas context syntax

5. You want to display multiple lines of text on an OLED screen using luma.oled. Which approach correctly updates the display with two lines: 'Line 1' at (0,0) and 'Line 2' at (0,15)?

hard

A. Use one canvas context and call draw.text((0,0), 'Line 1') and draw.text((0,15), 'Line 2') inside it

B. Call canvas(device) twice, each time drawing one line separately

C. Draw 'Line 1' outside canvas context and 'Line 2' inside canvas

D. Use draw.text((0,0), 'Line 1\nLine 2') to print both lines at once

Solution

1. Step 1: Understand canvas context usage

   All drawing commands must be inside one canvas context to update the display at once.

2. Step 2: Draw multiple lines with separate coordinates

   Calling draw.text twice inside the same canvas with different y-coordinates correctly places two lines.

3. Final Answer:

   Use one canvas context and call draw.text((0,0), 'Line 1') and draw.text((0,15), 'Line 2') inside it -> Option A

4. Quick Check:

   Multiple texts inside one canvas = B [OK]

Hint: Draw all text lines inside one canvas context [OK]

Common Mistakes:

• Opening multiple canvas contexts causing flicker
• Trying to print multiline string with \n directly
• Drawing outside canvas context