Sending numbers between two micro:bits by radio

The idea

Two digital systems can transmit data to each other by radio, and a shared group number keeps each pair's messages apart from the rest of the class.

What you need

• 2 BBC micro:bits per pair, each with a battery pack holding 2 AAA cells
• 1 USB cable and a computer with the MakeCode editor
• A list giving each pair its own radio group number (1 to 30 for a class)
• Trundle wheel for the playground test (the range at power 7 can reach 70 m, longer than most tape measures)

How to do it

1. Program both micro:bits the same way: on start, set the radio group to your pair's number and set the transmit power to 7; when button A is pressed, send a random number from 0 to 9 and show it; when a number is received, show it.
2. Stand 1 m apart and press A 10 times. Record the number shown on each micro:bit each time.
3. Change one micro:bit's group number to a neighbour's and press A again. Record who receives it.
4. Change it back. In the playground, step apart 2 m at a time until messages stop arriving. Record the distance where 10 out of 10 messages still arrive.
5. Change the transmit power to 0 in both programs, download them again and repeat the distance test.
6. Explain, with a drawing, how the number travels from one micro:bit to the other.

What you should see

Within the classroom every number shown on the receiver matches the number sent. Pairs on different groups do not receive each other's numbers; two pairs on the same group see each other's numbers, which shows why the group setting matters. MakeCode documents transmit power from 0 to 7 (default 6) and a range of up to 70 m at full power in open space, and a program that never sets the power sends at the default 6, so the power has to be set for the power 7 test; at power 0 messages stop arriving at a much shorter distance, and walls and people in between shorten both ranges. The learner knows it worked when they can explain why a neighbour on the same group received their message.

What changes

What you change

transmit power (0 or 7)

What you measure

the greatest distance at which 10 of 10 messages arrive

What you keep the same

• the same pair of micro:bits and fresh cells
• the same open area
• held at the same height, screens facing each other

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

• Radio messages go only to the micro:bit you are pointing at (every micro:bit on the same group in range receives them).
• Data travels through a wire hidden in the air (radio waves need no wire).
• A message either arrives perfectly or not at all, so range does not matter (near the edge of range some messages are lost).

Safety card

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

• Science and Technology K–6 Syllabus (2017), NESA. The syllabus taught in 2026; the 2024 syllabus replaces it from 2027. Code read from the official syllabus document (DOCX) on 2026-09-22.ST2-11DI-T
• Science and Technology K–6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.ST2-DDT-02
• Australian Curriculum v9AC9TDI4K02AC9TDI4P04

Sources

The pages the author read to write this activity.

1. www.nsw.gov.au/education-and-training/nesa/curriculum/science/science-and-technology-k-6-2017
2. curriculum.nsw.edu.au/learning-areas/science/science-and-technology-k-6-2024/outcomes
3. makecode.microbit.org/reference/radio
4. makecode.microbit.org/reference/radio/set-group
5. makecode.microbit.org/reference/radio/set-transmit-power
6. www.digitaltechnologieshub.edu.au/search/networking-with-the-micro-bit