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A utility for flashing the BBC micro:bit with Python scripts and the MicroPython runtime. You pronounce the name of this utility "micro-flash". ;-)

It provides three services:

  1. A library of functions to programatically create a hex file and flash it onto a BBC micro:bit.
  2. A command line utility called uflash that will flash Python scripts onto a BBC micro:bit.
  3. A command line utility called py2hex for creating hex files from Python scripts and saving them on the local filesystem

Several essential operations are implemented:

  • Encode Python into the hex format.
  • Embed the resulting hexified Python into the MicroPython runtime hex.
  • Extract an encoded Python script from a MicroPython hex file.
  • Discover the connected micro:bit.
  • Copy the resulting hex onto the micro:bit, thus flashing the device.
  • Specify the MicroPython runtime hex in which to embed your Python code.


To install simply type:

$ pip install uflash

...and the package will download from PyPI. If you wish to upgrade to the latest version, use the following command:

$ pip install --no-cache --upgrade uflash

NB: You must use a USB data cable to connect the micro:bit to your computer (some cables are power only). You're in good shape if, when plugged in, the micro:bit appears as a USB storage device on your file system.

Linux users: For uflash to work you must ensure the micro:bit is mounted as a USB storage device. Usually this is done automatically. If not you've probably configured automounting to be off. If that's the case, we assume you have the technical knowledge to mount the device yourself or to install the required kernel modules if they're missing. Default installs of popular Linux distros "should just work" (tm) out of the box given a default install.

Command Usage


To read help simply type:

$ uflash --help


$ uflash -h

To discover the version information type:

$ uflash --version

If you type the command on its own then uflash will attempt to find a connected BBC micro:bit and flash an unmodified default version of the MicroPython runtime onto it:

$ uflash
Flashing Python to: /media/ntoll/MICROBIT/micropython.hex

To flash a version of the MicroPython runtime with a specified script embedded within it (so that script is run when the BBC micro:bit boots up) then pass the path to the Python script in as the first argument to the command:

$ uflash
Flashing to: /media/ntoll/MICROBIT/micropython.hex

You can let uflash watch for changes of your script. It will be flashed automatically every time you save it:

$ uflash -w


$ uflash --watch

At this point uflash will try to automatically detect the path to the device. However, if you have several devices plugged in and/or know what the path on the filesystem to the BBC micro:bit already is, you can specify this as a second argument to the command:

$ uflash /media/ntoll/MICROBIT
Flashing to: /media/ntoll/MICROBIT/micropython.hex

You can even flash multiple devices at once:

$ uflash /media/ntoll/MICROBIT /media/ntoll/MICROBIT1
Flashing to: /media/ntoll/MICROBIT/micropython.hex
Flashing to: /media/ntoll/MICROBIT1/micropython.hex

To extract a Python script from a hex file use the "-e" flag like this:

$ uflash -e something.hex

This will save the Python script recovered from "something.hex" into the file "". If you don't supply a target the recovered script will emit to stdout.

If you're developing MicroPython and have a custom runtime hex file you can specify that uflash use it instead of the built-in version of MicroPython in the following way:

$ uflash -r firmware.hex


$ uflash --runtime=firmware.hex


To create output .hex files in the same directory as the input .py files:

$ py2hex tests/
Hexifying as: tests/example.hex

py2hex includes that same -r/--runtime and -m/--minify options as uflash and adds an additional option -o/--outdir:

To create output .hex files in a different directory:

$ py2hex -o /tmp
Hexifying as: /tmp/example.hex


$ py2hex --outdir /tmp
Hexifying as: /tmp/example.hex

py2hex can handle multiple input files:

$ py2hex
Hexifying as: a.hex
Hexifying as: b.hex
Hexifying as: c.hex


$ py2hex *.py
Hexifying as: a.hex
Hexifying as: b.hex
Hexifying as: c.hex


The source code is hosted in GitHub. Please feel free to fork the repository. Assuming you have Git installed you can download the code from the canonical repository with the following command:

$ git clone

Ensure you have the correct dependencies for development installed by creating a virtualenv and running:

$ pip install -r requirements.txt

To locally install your development version of the module into a virtualenv, run the following command:

$ python develop

There is a Makefile that helps with most of the common workflows associated with development. Typing make on its own will list the options thus:

$ make

There is no default Makefile target right now. Try:

make clean - reset the project and remove auto-generated assets.
make pyflakes - run the PyFlakes code checker.
make pep8 - run the PEP8 style checker.
make test - run the test suite.
make coverage - view a report on test coverage.
make check - run all the checkers and tests.
make package - create a deployable package for the project.
make rpm - create an rpm package for the project.
make publish - publish the project to PyPI.
make docs - run sphinx to create project documentation.


A module and command to easily flash Python onto the BBC's micro:bit device.







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