Skip to content
Switch branches/tags
Go to file

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time

MicroJIT is a Just-In-Time compiler for Alex Roger's Stack Virtual Machine on the BBC micro:bit. This repository contains all the software required to run the JIT compiler on a micro:bit and deploy Stack programs to it via a USB serial connection. You can see a video demonstration here.

The JIT compiler is written in C++ and generates Arm Thumb bytecode. Compiled programs are written to the micro:bit's flash, so you can reboot the device and run the same program — once the currently stored program has finished running you can deploy a new one, using the script described below.

Building & using

Please note that the following has only been tested under macOS 10.13.

To get started, you'll need to configure your computer for offline micro:bit development. Please also ensure that you have Python 3+ installed. Clone this repository and run scripts/ from the root directory of the repository. This will download all the dependencies of the project and build the binary that you need to deploy to the micro:bit.

Once the binary is compiled, either copy build/bbc-microbit-classic-gcc/source/microjit-combined.hex to your micro:bit or run scripts/ (again, from the root directory). If you make any changes to the code you can also use scripts/ to rebuild and deploy the code to the binary.

The micro:bit software supports receiving new Stack programs via serial. If you have a file containing Stack code encoded in hexadecimal, run scripts/ -a [filename]. The -a flag indicates that the file is encoded in ASCII hexadecimal; if you have a binary file instead run scripts/ [filename]. Run scripts/ --help to see more options.

Please note that this script closes the serial connection when it terminates. Closing the connection causes the micro:bit to reboot, which will mean your program restarts. You can pass a flag -t [seconds] to scripts/ that will optionally pause the script, giving the micro:bit sufficient time to run your program before rebooting. This also has the annoying effect of running your program twice.

You may prefer to use an adapted version of the Stack website running locally on your computer. This uses the same code for serial transmission, but keeps the serial connection open whilst the web server is running. It also allows you to use Alex Roger's programming environment directly with the micro:bit.

Running tests

There are around 400 unit tests that run on the micro:bit. To test the project, change Mode in source/Config.h to ProjectMode::UnitTests or ProjectMode::OptionalInstructionTests.

License & contributing

The contents of this repository is available under the MIT License. The Stack Virtual Machine is © Alex Rogers 2017.

The contents of this repository represents all the code that I wrote for my undergraduate thesis; as such I cannot accept pull requests until after the examiners have had the opportunity to look at it (July 2018).


A JIT compiler for the BBC micro:bit





No releases published


No packages published