[python-uk] PYCON UK Python-on-a-chip

G Bulmer UK gbulmeruk at yahoo.co.uk
Mon Oct 3 17:09:29 CEST 2011

Good news for folks who were interested in Python on Microcontrollers  
at PYCON UK (and anywhere else :-)

The "best" implementation that I have found so far is "Python-on-a- 
chip" (P14p)
A project lead by Dean Hall. (If you know of something better, please,  
please tell me)

Why "best":
1. It already works
2. P14p is runs in about 55 KB+ program memory (flash) and 8KB RAM (to  
be useful), so just about fits on an Arduino Mega, and definitely fits  
in slightly bigger MCUs.

It does have some missing features:
My Python is so poor, that I feel uncomfortable. I have no problem  
with 'exec' being missed out :-)

I do feel uncomfortable (in theory) about 'try', 'except' and  
'finally' being missing, but  they do feel like pretty sophisticated  
concepts to use on a microcontroller. I first saw exceptions in Green,  
which became the Ada programming language, a language explicitly  
designed for embedded programming. I saw them again in C++, then Java  
(I've tried to teach all of them at undergraduate and post grad). IMHO  
it requires programming maturity to use them well, but I am always  
unhappy to use "cut-down" implementations in order to teach something.

If anyone can find the time, I'd be grateful if folks would tell me if  
they think I am "barking up the wrong tree" (or simply "barking":-) by  
focusing on P14p.
In the absence of guidance, I will try to keep chipping away:-)

Anyway, while PYCON UK was happening (down the pub:-), 'Dave' of  
LeafLabs published this small, but encouraging blog:

He has got interactive PyMite (part of Python-on-a-chip) working on an  
STM32F103 (ST Micro Cortex-M3 ARM) "Maple" !

I base my boards on the LeafLabs work, so this is excellent news. I  
missed this blog until Monday, so I apologise if anyone at PYCON UK  
feels I was asking questions unnecessarily.

I currently use Arduinos C/C++ and the Arduino libraries for my  
workshops, but I am trying to move to the much more powerful ARM  
microcontroller; there are some projects which people ask about which  
are much more practical on faster, 32-bit MCUs with better peripherals.

LeafLabs IDE is a fork of Processing (the base for the Arduino-IDE)  
and uses the same gcc C/C++ toolchain, but with LeafLabs libraries, so  
it isn't a big leap from Arduino.

As folks who have done Microcontroller development will tell you,  
debugging C/C++ code on a microcontroller without hardware debug  
support can get quite hard. I don't use hardware debug with kids for a  
bunch of reasons (I'm happy to explain if anyone asks).

So, being able to debug a live program, by printing variables, or  
running fragments of code, in the same programming language as the  
program is a significant step forward :-)
I think that might be teachable. Actually, I think it might offer a  
completely different way to learn.

Please don't assume I think this is "the way" to get Python into the  
hands of learners. I think people learn for many reasons, with many  
goals. This *broadens* the reach of Python (to include me and smaller  
MCUs:-). Of course, I still need to understand it!


PS - Bog thank you to people for encouraging my microcontroller  
efforts in education (children and adults) at PYCON UK

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