Micro:bit Compass & Direction Finder (Python)

Learning Objectives

By the end of this lesson, students will be able to:

• Use the Micro:bit’s built-in compass sensor in Python.
• Calibrate the compass with compass.calibrate().
• Convert the compass heading (0–359°) into the four main directions: N, E, S, W.
• Display the correct direction on the LED screen.

1. Concept Overview

The Micro:bit has a built-in magnetometer (compass sensor) that can measure the Earth’s magnetic field and give you a heading from 0° to 359°, where:

• 0° ≈ North
• 90° ≈ East
• 180° ≈ South
• 270° ≈ West

But the compass is not accurate until you calibrate it using:

compass.calibrate()

During calibration, students will tilt the Micro:bit and draw a pattern on the LED display. After calibration, the compass will return more accurate heading values.

2. Spec Sheet (Student-Friendly)

Program Name: P1_lastname_compassDirection.py
Device: Micro:bit v2
Language: Python (MicroPython)

Program Requirements

1. Calibration:
   • When the program starts, it must call compass.calibrate() once.
2. Compass Reading:
   • Repeatedly read the compass heading with compass.heading().
   • Heading is an integer from 0 to 359.
3. Direction Ranges:
   • North (N): 315°–359° and 0°–44°
   • East (E): 45°–134°
   • South (S): 135°–224°
   • West (W): 225°–314°
4. Output:
   • Display N, E, S, or W on the LED matrix depending on the heading.
   • Update the direction repeatedly as the Micro:bit is rotated.
5. Looping:
   • The program must run in an infinite loop until the Micro:bit is reset.
6. Timing:
   • Add a small delay (e.g., 200 ms) between readings to avoid flickering and to save power.

3. Pseudocode

START

IMPORT microbit library and compass

CALL compass.calibrate()  // user tilts Micro:bit to complete calibration

REPEAT FOREVER:
    GET current_heading from compass.heading()  // result is 0 to 359

    IF heading < 45 OR heading >= 315:
        direction = "N"
    ELSE IF heading < 135:
        direction = "E"
    ELSE IF heading < 225:
        direction = "S"
    ELSE:
        direction = "W"

    DISPLAY direction letter on the LED screen
    WAIT 0.2 seconds

END REPEAT
END

4. Final Python Code (Micro:bit v2)

Students can copy this into the Micro:bit Python editor (or Mu) and download it to their boards.

from microbit import *
import compass

# Step 1: Calibrate the compass once at the start
compass.calibrate()

while True:
    # Step 2: Read the current heading (0 - 359 degrees)
    heading = compass.heading()
	************ more is needed ***********







    # Step 4: Small delay so the display does not flicker too fast
    sleep(200)

5. Step-By-Step Student Instructions

1. Open the Editor
   • Go to the Micro:bit Python editor or Mu editor.
   • Create a new file and name it P1_lastname_compassDirection.py.
2. Type the Code
   • Type the Python program.
   • Check for capitalization and spelling (especially compass.calibrate() and compass.heading()).
3. Flash to Micro:bit
   • Download the .hex file to the Micro:bit.
   • After flashing, the Micro:bit will ask you to calibrate the compass:
     • Tilt and move the Micro:bit until the pattern is complete.
4. Test the Direction Finder
   • Hold the Micro:bit flat like a compass.
   • Rotate your body slowly:
     • Check that N shows when facing North.
     • Rotate to find E, S, and W.

6. Required Challenge

If you want to push your stronger students:

1. Add Diagonal Directions
   • Add NE, SE, SW, NW using smaller angle ranges.
   • Hint: You can scroll text like "NE" using display.scroll("NE").
2. Arrow Images Instead of Letters
   • Use Image.ARROW_N, Image.ARROW_E, etc. (or custom arrow images) instead of letters.
3. Direction + Degrees
   • Use display.scroll(str(heading)) to show the actual degree value occasionally.
4. Compass Game
   • Randomly choose a direction (N, E, S, W).
   • Have the Micro:bit show ?, and the player must rotate until they face that direction.

7. Reflection Questions. Must answer questions to get secret work.

Have students answer in 2–3 sentences each:

1. Why does the Micro:bit need to be calibrated before using the compass?
2. How did you decide the angle ranges for N, E, S, and W?
3. How could a compass program like this be useful in a real-world project (e.g., navigation, robotics)?