Your BBC micro:bit comes with an accelerometer. It measures movement along three axes:
- X - tilting from left to right.
- Y - tilting forwards and backwards.
- Z - moving up and down.
There is a method for each axis that returns a positive or negative number indicating a measurement in milli-g’s. When the reading is 0 you are “level” along that particular axis.
For example, here’s a very simple spirit-level that uses
get_x to measure
how level the device is along the X axis:
from microbit import * while True: reading = accelerometer.get_x() if reading > 20: display.show("R") elif reading < -20: display.show("L") else: display.show("-")
If you hold the device flat it should display
-; however, rotate it left or
right and it’ll show
We want the device to constantly react to change, so we use an
while loop. The first thing to happen within the body of the
loop is a measurement along the X axis which is called
the accelerometer is so sensitive I’ve made level +/-20 in range. It’s why
elif conditionals check for
> 20 and
< -20. The
else statement means that if the
reading is between -20 and 20 then
we consider it level. For each of these conditions we use the display to show
the appropriate character.
There is also a
get_y method for the Y axis and a
get_z method for the
If you’ve ever wondered how a mobile phone knows which up to show the images on its screen, it’s because it uses an accelerometer in exactly the same way as the program above. Game controllers also contain accelerometers to help you steer and move around in games.
One of the most wonderful aspects of MicroPython on the BBC micro:bit is how it lets you easily link different capabilities of the device together. For example, let’s turn it into a musical instrument (of sorts).
Connect a speaker as you did in the music tutorial. Use crocodile clips to attach pin 0 and GND to the positive and negative inputs on the speaker - it doesn’t matter which way round they are connected to the speaker.
What happens if we take the readings from the accelerometer and play them as pitches? Let’s find out:
from microbit import * import music while True: music.pitch(accelerometer.get_y(), 10)
The key line is at the end and remarkably simple. We nest the reading from
the Y axis as the frequency to feed into the
music.pitch method. We only
let it play for 10 milliseconds because we want the tone to change quickly as
the device is tipped. Because the device is in an infinite
while loop it
is constantly reacting to changes in the Y axis measurement.
Tip the device forwards and backwards. If the reading along the Y axis is positive it’ll change the pitch of the tone played by the micro:bit.
Imagine a whole symphony orchestra of these devices. Can you play a tune? How would you improve the program to make the micro:bit sound more musical?