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Forth for the BBC micro:bit

BBC micro:bit

There was an opportunity to have early access to a spare BBC micro:bit.

Matthias Koch took the time and effort to adapt his Mecrsip-Stellaris Forth to the BBC micro:bit hardware.

The complete Mecrisp Github File System contains many files covering the different Controllers it runs on – but which are not necessarily related to the micro:bit.

We want to make it easy to get to the stage of running the first Forth code on the micro:bit.

As result here a Starter Pack.

Suggestions to improve it are welcome.

How do you install Mecrisp onto the micro:bit?

  • The Serial Interface needs to link with TeraTerm1) software making the PC a display and keyboard for the micro:bit. Make shure you installed TeraTerm. Now get the Starter Pack with:
  • The Mecrisp Forth hex file to throw into the microbit folder on the PC for programming the micro:bit.
  • A small example VFXTESTAPPbit.f ASCII file adapted to the existing Microbit Mecrisp Hex File,
    1. The same VFXTESTAPPbit file as Doc for own documentation and extension.
    2. More documentation about the small VFXTESTAPP Forth starting example for PC just using 35 Forth Words with explanations can be found here.
    3. And you can try the VFXTESTAPP example on the PC without any micro:bit by just downloading and starting the vfxtestapp.exe
    4. micro:bit IO Connection Documentation generated by Matthias Koch as there are no official schematics.

    More I/O Discussions about the micro:bit in English and as well available in German ( not including Forth but a lot of IO information ) as supporting information and part of the Forth Bookshelf is here.
    Have fun trying it out and feedback for additions and improvements can be sent to Juergen Pintaske at


Hardware - All the bits and pieces that make up your BBC micro:bit.

All the BBC micro:bit pins
More details about your BBC micro:bit : Specs & Schematic.

Or visit Mo McRoberts, Lead technical architect for BBC Archive Development and BBC Datalab, at github: SCH_BBC-Microbit_V1.3B.pdf

Check - Hardware designs for the BBC micro:bit - as well.

Inofficial Schematic (PDF) - no warranty for correctness and completeness.

Calliope is the German Version


The same basic processor, and the best, the basic Mecrisp Forth Binary Matthias Koch did is identical for both systems.

Now all components are on one side, with added microphone and loudspeaker. The connector holes have been put at the end of the star shape – less risk of short circuits

Github with all of the data: in German, and in English .
You can buy it here
Price is a bit higher – but contains components that you have to buy separately with micro:bit.

2 Files as a first step on how the Calliope IO works. Thanks to Matthias Koch for the code and Carsten Strotmann for bringing a Calliope.


There is an eBook in German and English – not about Forth yet but a lot of examples and background information. And showing small examples that work in other languages, and that can be re-implemented in Forth on both boards as programming exercise.

How to Start? – Go to A Start With Forth here - most of the relevant eBook contents:

The full eBook is available here for easy read on the mobile

More Clones

There are microbit clones around , but they are probably not compatible with the mecrisp version described here.


Enjoy these systems; how to use the Bluetooth with Forth will be shown later when there is time.

not included in the Starter Pack - TeraTerm download (Heise 2017)
en/projects/microbit/start.txt · Last modified: 2022-10-20 09:59 by juergenuk