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A REPL client for MicroPython running on the BBC micro:bit.

Project description

This script lets you run commands directly onto a connected micro:bit device. Put simply, you get to program the micro:bit in real time, just like we used to with the old BBC micro from the 1980’s. This encourages exploration, experimentation and a sense of adventure. It’s also a good way to play with the device to learn about its capabilities.

The script detects the port to which the micro:bit is connected and uses PySerial to make a connection to the micro:bit’s Read Evaluate Print Loop (REPL).

For more information about what a REPL, is check out this Wikipedia article:


Unfortunately, Windows does not come with serial/COM drivers for the micro:bit installed by default (happily, Linux and OSX do).

If you’re on Windows, in order to make this work you should use the mbedWinSerial_16466.exe file (found in the root directory of this project) to install the correct drivers. You MUST have your micro:bit plugged into your computer when you run this command.

For more information and the latest versions of this driver please visit:

Assuming this requirement is met, you can install/run the script in three ways:

  1. Install via pip and PyPI:

    # pip install microrepl
  2. Install via

    # python install
  3. Run the script from within the repository:

    # pip install -r requirements.txt
    # python

All of the above should probably be done within a virtualenv. The first two options will result in two commands being installed: microrepl or its alias urepl. Simply type these at the command prompt to run the application.

Getting Started

When you run the script it will try to be as helpful as possible in working out why it can’t connect. In most cases it will try to print some helpful advice.

Once connected the script will stop the program running on the micro:bit in order to drop you into the REPL itself. You type Python commands next to the prompt (>>>).

If things don’t seem to be working, re-flash your micro:bit using the firmware.hex file in this directory, and try again.

You can use the TAB key to auto-complete words. For example, if you type then hit TAB, MicroPython will helpfully complete the word for you, like this: microbit.screen.

You can move forwards and backwards through your command history by using the up arrow key (to move back through your command history) and down arrow key (to move forwards through your command history). The left and right arrow keys allow you to move through the text of your command without deleting it.

Use the TAB and arrow key commands! They save a lot of typing and look really cool.

Unplugging the device and pressing the reset button will re-start the program as the version you originally flashed onto the device.

Useful Commands

A good place to start is to type help(). From here you should be able to explore the device and the MicroPython version of Python 3.

All the micro:bit’s hardware is available to program via the microbit module. To start using it type the command import microbit. Do fun things such as microbit.display.scroll('Hello, World!') and watch the device react in real-time.

Type the command dir() to see a list of all the things currently available to you - this includes the various classes and functions for the program you may have already flashed onto the micro:bit.

Find Out More

To learn more about the amazing MicroPython visit:

The BBC micro:bit’s (non-Pythonic) home is:

To learn about the Python language visit:

Release History


Updated to latest version of PySerial.


Windows support added. Requires installation of drivers found in the mbedWinSerial_16466.exe executable. More information can be found at the ARM website:


Initial release. Works on Linux and OSX on both Python 2.7 and 3.3+. Windows version coming soon.

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