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Radio

On this page we will learn

  • how the micro:bit radio works
  • how to turn the radio on and choose a group
  • how to send and receive messages between micro:bits

Terminology

  • radio – a way of sending and receiving messages without wires, using invisible radio waves.
  • wireless – communicating between devices without any cables or wires.
  • group – a number from 0 to 255 that sets which micro:bits can hear each other's radio messages.
  • queue – a line of waiting items where the oldest one is dealt with first, like received radio messages.
  • None – a special Python value meaning nothing, such as when no radio message has arrived.

The radio sends and receives short wireless messages between micro:bits.

Possible uses:

  • multiplayer games
  • voting systems
  • remote controls
  • wireless sensors

Connect it

The radio is built into the micro:bit, so we don't need to connect anything. We need at least two micro:bits.

  • Each example is a main.py file. See Your First Program for how to create, upload and run it. Upload the program to each micro:bit.
  • Micro:bits only hear messages from micro:bits in the same group (0–255). Pick a group that other students aren't using.
  • Received messages wait in a queue, like people in a line: the oldest message is read first. If the queue is full, new messages are lost.

How radio works

Imagine you and a friend on opposite sides of the classroom, each with a torch. By flashing the torch in an agreed code you can send "HELLO" without any wires. Radio works the same way, but uses invisible radio waves instead of light.

Set it up

The radio has its own module. We import it after the microbit library:

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from microbit import *
import radio

Methods

Method Parameters Returns Description
radio.on() none none Turns the radio on. It is off by default to save power.
radio.config(group=0) group: 0–255 none Sets the group. Only micro:bits in the same group hear each other.
radio.send(message) message: string none Sends a message to every micro:bit in the group
radio.receive() none string or None The oldest message in the queue, or None if there are none

radio.on()

Turns the radio on. It is off by default to save power, so every radio program needs this.

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from microbit import *
import radio

# Setup
radio.on()

# Main loop
while True:
    display.show(Image.YES)

PRIMM

  1. Predict what you think will happen. Be specific.
  2. Run the program.
  3. Time to investigate the code. What does each line do?
Code explanation
  • line 1 → imports all the commands from the microbit library.
  • line 2 → imports the radio module.
  • line 5 → turns the radio on.
  • line 8 → starts an endless loop.
  • line 9 → shows a tick to show the radio is ready.

radio.config()

Changes the radio settings. The most useful setting is group, which chooses which micro:bits can hear each other.

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from microbit import *
import radio

# Setup
radio.config(group=7)
radio.on()

# Main loop
while True:
    display.show(7)

PRIMM

  1. Predict what you think will happen. Be specific.
  2. Run the program.
  3. Time to investigate the code. What does each line do?
Code explanation
  • line 1 → imports all the commands from the microbit library.
  • line 2 → imports the radio module.
  • line 5 → sets the radio group to 7.
  • line 6 → turns the radio on.
  • line 9 → starts an endless loop.
  • line 10 → shows the group number.

radio.send()

Sends a message to every micro:bit in the same group.

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from microbit import *
import radio

# Setup
radio.config(group=7)
radio.on()

# Main loop
while True:
    if button_a.was_pressed():
        radio.send("happy")

PRIMM

  1. Predict what you think will happen. Be specific.
  2. Run the program.
  3. Time to investigate the code. What does each line do?
Code explanation
  • line 1 → imports all the commands from the microbit library.
  • line 2 → imports the radio module.
  • line 5 → sets the radio group to 7.
  • line 6 → turns the radio on.
  • line 9 → starts an endless loop.
  • line 10 → checks if button A was pressed.
  • line 11 → if it was, sends the message "happy" to group 7.

radio.receive()

Returns the oldest message waiting in the queue, or None if no messages have arrived.

Run this on a second micro:bit while the first runs the send() example.

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from microbit import *
import radio

# Setup
radio.config(group=7)
radio.on()

# Main loop
while True:
    message = radio.receive()
    if message == "happy":
        display.show(Image.HAPPY)

PRIMM

  1. Predict what you think will happen. Be specific.
  2. Run the program.
  3. Time to investigate the code. What does each line do?
Code explanation
  • line 1 → imports all the commands from the microbit library.
  • line 2 → imports the radio module.
  • line 5 → sets the radio group to 7.
  • line 6 → turns the radio on.
  • line 9 → starts an endless loop.
  • line 10 → gets the oldest message in the queue (or None) and stores it in message.
  • line 11 → checks if the message is "happy".
  • line 12 → if it is, shows a happy face.

Documentation

Documentation is the official guide written by the people who made the code library, and we can use it to look up every method and its parameters, including ones that aren't covered on this page.

Exercises

PRIMM

Time to modify the code and see what happens.

Starter files are in the radio folder of your tutorial files. Solutions are on the Exercise Solutions page.

Exercise 1

Starter: radio/ex1_pass_image (both micro:bits)

Can you move an image between two micro:bits? When the micro:bit showing the image is shaken, the image should disappear and appear on the other micro:bit.

Exercise 2

Starter: radio/ex2_yes_no (both micro:bits)

Can you send a private yes or no answer? Your program should:

  • press A to send yes, or B to send no
  • show the answer on the other micro:bit for half a second
  • use a group so nearby micro:bits don't receive your answer

Exercise 3

Starters: radio/ex3_outside and radio/ex3_inside

Can you make a wireless thermometer? It should work like this:

  • the outside micro:bit sends its temperature every 5 seconds
  • the inside micro:bit shows its own temperature when button A is pressed, and the latest outside temperature when button B is pressed