Introduction: Simple DND Doorbell System With Two Micro:bits

During the corona quarantaine, a lot of children are kept at home and a lot of people are working from home.

A challenging situation where children are asked at certain moments not to disturb the people making conference calls or giving a remote lecture.

The block level code is very simple, so this can be a perfect project to do with your kids in the moments before your very important conference call. ;)

Step 1: Demo of the Finished System

This system uses two Micro:bits (credits to Gerben Dierick for the idea).

  • One micro:bit (the sender, left one in the video) is attached at the door of the room where the conference call is made. The room where no one can disturb the people inside.
  • The second micro:bit (the receiver) is placed visible on the desk of the person inside that room.

The caller outside the room presses button A, the receiver inside the room then can choose A (ok, come in) or B (not ok, busy, stay out) to answer.

Step 2: Preparing to Program the Micro:bit

  • Go to
  • In the middle bar, choose 'advanced' en then at the bottom 'extensions'
  • Click the extension 'radio-broadcast'
  • Connect your micro:bit with the usb cable

Instructions on how to get the code on your micro:bit are available on the website.

Step 3: Programming the Sender

The complete blockcode can be found here.

Alternatively, you can upload the compiled hex-file in the browser to see the code.

Step 4: Programming the Receiver

The same with the receiver side

Step 5: Done

Connect the batteries and install the sender at your door.

Done ;)

(I don't know how long the batteries will last, if you're anxious about this, you can also use a batterypack with a usb cable)