Recording and Playback

With the built-in microphone and speaker, simple recording and playback is possible.

KOI can record a 3 second audio clip and saves the file as a wav format.

Install an SD Card


The pictures are stored onto an SD card, without an SD card, these operations would fail.

Recording and playback


Load KOI Extension:

Loading Extensions

Blocks for recording and playback:


Sample Program:


Program Flow

Download the program to Micro:bit.

  1. Press button A on the Micro:bit, KOI will record what you say.

  2. Press button B on the Micro:bit, KOI will playback the audio file.

Sample Code

Recording and playback (Extension0.5.7)

Extension Version and Updates

There may be updates to extensions periodically, please refer to the following link to update/downgrade your extension.

Makecode Extension Update


1: There is no reaction after pressing the buttons on the Micro:bit.

· A: This is because KOI has a longer boot time than Micro:bit. When the power is turned on, Micro:bit has already ran the code for KOI initialization before KOI is ready.

· Solution: Reset your Micro:bit after KOI has been turned on. (The trick is to let KOI power on completely before initialization.)

2: Does KOI work with 3V input?

· A: No, KOI only works with 5V.

3: Can I change the recording duration?

· A: No, because recording duration is limited by the amount of RAM that KOI has.

4: Can I play mp3 files on the KOI?

· A: No, KOI can only play wav files, and file size cannot exceed 512KB.

5: Can I create my own wav files to play on KOI?

· A: Yes but make sure the duration is less than 3.75 seconds with a bitrate of less than 512kbps. The file size has to be within 512KB.