Python on a chip

Python on a Chip PyMite, a Python Virtual Machine Jeremy Stott jeremy@stott.co.nzKiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Microcontrollers• Programming Microcontrollers is fun!• You can build your own toys / evil robots• Even getting lights to blink is fun• Usually programmed in C, sometimes C++ http://lighttrees.com/wordpress/archives/category/sculpture Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Whats wrong with C?! #include <stdio.h> int l;int main(int o,char **O,• Nothing is wrong with C int I){char c,*D=O[1];if(o>0){ for(l=0;D[l ];D[l ++]-=10){D [l++]-=120;D[l]-=• Its up to the programmer to write good 110;while (!main(0,O,l))D[l] += 20; putchar((D[l]+1032) code /20 ) ;}putchar(10);}else{ c=o+ (D[I]+82)%10-(I>l/2)* (D[I-l+I]+72)/10-9;D[I]+=I<0?0• Programmers may suffer from object :!(o=main(c/10,O,I-1))*((c+999 )%10-(D[I]+92)%10);}return o;} oriented withdrawal syndrome• Prolonged use of C may cause inappropriate outbursts of semi-colons;• You cant do [Python reference] in C http://www0.us.ioccc.org/years.html#2001 Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Introducing: Python-On-A-Chip● http://code.google.com/p/python-on-a-chip/● A project developing PyMite, a Python Virtual Machine designed to run on Microcontrollers● A small growing group > 256 mailing list members● Uses 55KB of ROM and 5KB of RAM for "Hello World!"● License: ● Tools: GNU LGPL v2.1 (Lesser GPL) ● Virtual Machine: GPL v2 (Non Commercial) Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

FeaturesIt Does:• Support integers, floats, lists, dicts, functions, modules, classes, generators, decorators and closures• Support 25 out of 29 keywords and 89 out of 112 byte codes from Python 2.6• Stackless green threadsIt Doesnt:• Have a built in compiler• Support any of Pythons standard libraries Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

25 out of 29 Keywords?PyMite supports the following set of Pythons keywords and assert break class continue def del elif else for from global if import in is lambda not or pass print raise return while yieldPyMite does not support these keywords except exec finally tryHowever, they are working on Exceptions Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

No Standard Libraries?Instead of supporting Pythons libraries, PyMite offer its own setof modules. Some of which have the same name as theirPython counterparts. PyMite Modules dict func list string sysAs well as many built in functions abs(x), bytearray(seq), bytearray(len), chr(i), eval(co), globals(), id(o), len(obj), locals(), map(f,s), ord(c), pow(x,y), range(...), sum(s), type(obj) Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Other Interesting Bits• PyMite only supports 8-bit character strings, so no Unicode• PyMite supports 32-bit signed integers, floats (if enabled) but not longs• You cant override type operators. Eg __add__() doesnt override + Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Installing under Ubuntu 11.04The easiest way to get PyMite is to check it out using Mercurial:$ hg clone https://code.google.com/p/python-on-a-chip/Install Python 2.6, setuptools and virtualenv$ sudo apt-get install python2.6 python-setuptools$ sudo easy_install virtualenvCreate the virtual environment and activate it$ virtualenv -p python2.6 --no-site-packages ./pymite$ source pymite/bin/activate Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Windows? AlmostDownload GNU Make, Python 2.6, SetupTools, and VirtualEnvhttp://gnuwin32.sourceforge.net/packages/make.htmhttp://www.python.org/getit/releases/2.6.6/http://pypi.python.org/pypi/setuptoolsInstall and add their paths to your Path Environment Variablec:Python26c:Python26Scriptsc:Program FilesGnuWin32binInstall and activate VirtualEnv> easy_install.exe virtualenv> virtualenv.exe --no-site-packages c:pymite> c:pymiteScriptsactivate.batAnd then you install a C compiler... Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Interactive PromptTo compile for the desktop and launch the interactive prompt$ make ipm(make sure you have activated the Python2.6 VirtualEnv)Test it outipm> class Robot():.... def walk(self, direction):.... print "Walking %s" % (direction,)....ipm> pybot = Robot()ipm> pybot.walk("to the shops")Walking to the shops Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Microcontrollers?mBed Microcontroller• 32-bit ARM Processor• Built-in USB interface• Powered via USB• Implements a Mass Storage Device, so programming is as easy as copying the binary onto the Flash drive• Many peripherals eg Ethernet, USB, Can, SPI, etc…• Online Compiler Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Robots!m3pi from Pololu•Easy to set up•Ideal for getting started•Cost:– m3pi Robot $150 USD– mbed Micro $60 USD•Surprisingly Fast!! Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

What about Wireless?Nobody likes to follow their robot around with a laptop…The m3pi has a handy slot for a Digi Zigbee module.But these $35 WiFi modules fit in the same slot:RN-XV from Roving Networkshttp://rovingnetworks.com/XVee.php• Have the same pin-out• Support WPA2• Make the project awesome! Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Putting it all togetherCompile PyMite for the mbed target$ make PLATFORM=mbedImport the resulting .zip archive into the mbed IDEImport the m3pi library into the mbed IDECompile and save the binary onto the mbed microcontrollerTurn on the Robot and connect to the ipm using a pythonsocket$ tools/ipm.py –-ipaddress 192.168.1.3 –-port 2000 Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Thank You Any Questions?Kiwi Pycon 2011 Python on a Chip jeremy@stott.co.nz

Python on a chip

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