Built-in Sensors on BBC micro:bit

Built-in Sensors Overview

The micro:bit V2 has an impressive suite of built-in sensors ߀” no external wiring required:

Sensor	MicroPython object	What it measures
Accelerometer	accelerometer	Tilt, shake, acceleration on X/Y/Z
Magnetometer (compass)	compass	Magnetic heading (0߀“360?°)
Temperature	temperature()	Approximate ambient temperature via CPU die
Microphone	microphone	Sound level, loud/quiet events (V2 only)
Touch logo	pin_logo	Capacitive touch (V2 only)

Accelerometer

Reads acceleration in milli-g (1000 = 1g = 9.8 m/s?²):

from microbit import *

while True:
    x = accelerometer.get_x()   # Left/right tilt
    y = accelerometer.get_y()   # Forward/back tilt
    z = accelerometer.get_z()   # Up/down (gravity ߉? -1024 when flat)
    print(x, y, z)
    sleep(200)

Tilt Detection

while True:
    x = accelerometer.get_x()
    if x > 300:
        display.show("R")     # Tilted right
    elif x < -300:
        display.show("L")     # Tilted left
    else:
        display.show("-")
    sleep(100)

Gesture Detection

The micro:bit firmware recognises common physical gestures:

while True:
    gesture = accelerometer.current_gesture()
    if gesture == "shake":
        display.show(Image.SKULL)
    elif gesture == "face up":
        display.show(Image.HAPPY)
    elif gesture == "face down":
        display.show(Image.SAD)

Available gestures: "shake", "up", "down", "left", "right", "face up", "face down", "freefall", "2g", "3g", "6g", "8g"

Compass

The magnetometer measures Earth's magnetic field. You must calibrate it first ߀” the micro:bit displays a mini-game asking you to tilt the board to fill all LEDs.

from microbit import *

compass.calibrate()   # Runs interactive calibration

while True:
    heading = compass.heading()   # 0߀“360 degrees (0 = North)
    print("Heading:", heading)
    sleep(500)

Compass Direction Display

directions = ["N", "NE", "E", "SE", "S", "SW", "W", "NW"]
idx = int((compass.heading() + 22.5) / 45) % 8
display.show(directions[idx])

Temperature

The temperature is read from the CPU die ߀” it tends to read slightly higher than ambient:

temp = temperature()    # Returns degrees Celsius as integer
display.scroll(str(temp) + "C")

Microphone (V2 only)

from microbit import *

while True:
    if microphone.was_event(SoundEvent.LOUD):
        display.show(Image.SURPRISED)
        sleep(1000)
        display.clear()
    if microphone.was_event(SoundEvent.QUIET):
        display.show(Image.ASLEEP)
        sleep(1000)
        display.clear()

Sound level as a number (0߀“255):

level = microphone.sound_level()
display.show(level // 30)   # Map to 0߀“8 for rough display

Speaker (V2 only)

from microbit import *
import music

music.play(music.RINGTONE)         # Built-in tune
music.play(["C4:4", "E4:4", "G4:4"])  # Note list

Notes format: "NoteOctave:Duration" ߀” e.g. "C4:4" = C in octave 4 for 4 ticks.

Combining Sensors

from microbit import *

while True:
    if accelerometer.was_gesture("shake"):
        display.scroll(str(temperature()) + "C")
    if button_a.was_pressed():
        compass.calibrate()
    sleep(100)