Subject:
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Python on the NXC
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 9 Feb 2008 08:05:59 GMT
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Original-From:
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Stargaming <stargaming@gmail.com*nomorespam*>
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Viewed:
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7172 times
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Hey robo folks,
Abstract: I want to run Python on the NXT, not on my PC and connect to
the NXC remotely. Did I understand the architecture correctly? Any hints
on translation?
As far as I know, the NXT is so far lacking support for high-level
languages running *natively*. There seems to be support for some by using
a custom firmware, for example `leJOS NXJ`_ (Java) and pbLua_ (Lua). [1]_
The common solution seems to be using a live Bluetooth or USB connection
to the NXT brick, sending bytecode instructions through a socket to
control the NXT from a high-level (actually, from *any*) language. [2]_
Now, well, I find having an USB cable connection rather sloppy and not
everyone has a Bluetooth device yet. So I figured I'd make high-level
languages (I'm mainly targeting Python, but see below) Just Work.
So, first off, let me see if I understood the flow of a NXT program:
Let's assume I start off with a NXC program. The NXC compiler will
translate it to NBC assembly code. The NBC compiler, in turn, will
translate it to bytecode. I can transfer this bytecode to my NXT brick
and let its virtual machine execute it there (this is much like the
normal flow of a C program on a PC, isn't it?).
Are my explanations right so far?
How could I let Python programs run on the NXT now? I can image following
solutions:
* Write a firmware. This might mean reimplementing the *whole* Python
architecture and generally sounds like a bad idea. The advantage would be
a more complete package.
* Bundle the Python interpreter (written in C) with the Python program.
Much like the way one would distribute Python files as Portable
Executables. Major drawback: Huuuuge Python interpreter on the tiny NXT
memory. I doubt this will work. One would *have to modify* the Python
interpreter and could strip off parts that aren't of any use on the NXT
anyways (for example unicode and all kinds of encodings) but I still
doubt this would work out so well.
* Write a translator from Python to NXC (as in: Python to C). So,
traverse a Python syntax token tree and yield NXC instructions (basic
flow should be the same). This might be the easiest but most error-prone
way to go. Chances are high someone already translated Python to C (in a
not-so-sophisticated, high-level way).
* Write a translator from Python bytecode to NXT bytecode. Since I
haven't looked into NXC bytecode yet, I don't know if this would work. A
quick glance on the `NXT Bytecode Reference`_ didn't look that promising.
The NXT bytecode looks closer to PC assembly than Python bytecode...
* Use PyPy to convert RPython (restricted, stripped-down Python) to NXC.
They already have a nice infrastructure to convert Python (and, as a
bonus, some other languages) to other backends, so this might work. As
far as I know, translation is quite expensive, though, thus this might
not be the best solution. Perhaps the Python interpreter could be
translated as well (translate interpreter once, read python files often),
but I guess this would yield the same problems as porting Python to the
NXT.
Any other ideas I have overlooked? Remarks on my ideas?
Thank you in advance,
Stargaming
.. [1] See "NXT Programming Software" in the `NXT Programming`_ overview
.. [2] See "NXT Off-Brick controllers (Remote Controls)" in the `NXT
Programming`_ overview.
.. _NXT Programming: http://www.teamhassenplug.org/NXT/NXTSoftware.html
.. _leJOS NXJ: http://www.lejos.org/
.. _pbLua: http://www.hempeldesigngroup.com/lego/pbLua
.. _NXT Bytecode Reference: http://cache.lego.com/upload/
contentTemplating/MindstormsOverview/otherfiles/2057/LEGO%20MINDSTORMS%
20NXT%20Executable%20File%20Specification(1)_9143FED4-3FF8-40B1-
A06F-78B530347A59.zip
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