overview.txt

What is Microbit - prototype technical overview
===============================================

NOTE; This, and all materials related to the reference implementation are
CONFIDENTIAL INFORMATION, and must not be made public, as per NDA with BBC.


The project entails a simple programmable wearable device. The current
reference implementation is based on an Atmel ATMega 32u4 which makes it
similar to an leonardo arduino - indeed we using the command line suite of
tools configured as a leonardo. (The device doesn't have an Arduino
bootloader however)

The user uses a website (which is implemented using Django) to create
programs for the device using Blockly. Blockly generates javascript to drive
a simulator for verification of the behaviour. Blockly also generates python
- that is stored on a server.

The python is compiled to C++ - using a barebone python to C++ compiler I've
written using David Beazeley's ply.

The C++ is then injected into the arduino command line tools, compiled and a
.hex file image extracted from the build

That .hex file can be downloaded by users
They then have a local application - a loader - (PyQT & shell out to a
command line tool) for loading the code onto the device.
The device then runs the code.

There's also an IOT library (http://github.com/sparkslabs/iotoy) which is
available to allow the device to be controlled and used as a sensor by a
host machine. The primary client side library for that is written in python.

Buried in that toolchain is a cut down python to C++ compiler intended for
targetting microcontrollers. (I did look at all the others I'm aware of, but
they weren't really suitable). 

There's also the aspect that actually while blockly is used as *a* editor,
the system's primary target is python.

While technologies are used in this reference implementation, please
rememeber it is illustrative, not prescriptive. The functional specification
is the canonical description of prescriptive functionality.

There are many some parts of this are not as fleshed out as they could be -
in particular the python/C++ code is nowhere near as far along as we'd like.
It works, but within more constrained limits than it should. 


Michael Sparks, Senior Research Engineer, BBC R&D, December 2014