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LEGO Mindstorms NXT Control Package

Project description

NXT-Python is a package for controlling a LEGO NXT robot using the Python
programming language. It can communicate using either USB or Bluetooth. It is
available under the Gnu GPL license. It is based on NXT_Python, where releases
halted in May 2007.


* Python 2.6 (
And at least one comm library:
* Bluetooth communications:
Linux/Windows: PyBluez (
(package python-bluez in deb-based linuxes)
Mac: LightBlue (
* USB communications:

Installation (if using source package):

* Untar/unzip source package
* In package directory, run "python install" (as root), or if
under windows, double-click install.bat.
* To use USB on Linux as non-superuser, at a root terminal type:
groupadd lego
usermod -a -G lego [username]
echo 'BUS=="usb", SYSFS{idVendor}=="0694", GROUP="lego", MODE="0660"' \
> /etc/udev/rules.d/70-lego.rules

Getting Started:

Take a look at the examples directory (this is, unfortunately, not included
in the windows installer will find it in a corresponding source
package or SVN checkout). Feel free to copy that code into your scripts and
don't be afraid to experiment! If you are having trouble with something, you may
find the solution in the docstrings (ex. help('nxt.sensor.Ultrasonic')) or even
in the source code (especially for digital sensors).

(I have tried to put the most important stuff first, but it would be a good
idea to read the whole section. In any case, read it all the way through
before asking for help. Thanks!)

-=-=-About v2-=-=-
This version is part of the 2.x series of releases. Programs designed for
NXT_Python or for the 1.x series of nxt-python will not work with this version.
If you are trying to get an old program to work, it most likely needs a 1.x
series release, which can be downloaded from the nxt-python downloads page at
googlecode. New projects should use a 2.x series release (hint: this is one!)
due to the new features and API improvements. Converting old projects is
somewhat difficult and not officially supported, though as always you're
welcome to ask for help.
Users who are upgrading from v1.x of nxt-python may notice that there is no
longer a nxt.server module. I removed it due to it being a prime example of
feature creep, the code being of low quality, and the connection protocol very
badly designed. I would recommend that anyone wanting to use a brick over a
network connection design and write their own protocol and code to best fit
their specific application.
-=-=-Problems and Their Solutions-=-=-
For some reason, digital sensor operations have a tendency to throw random
I2C communication errors. I have been unable to find the source of this problem
(it seems to be inside the nxt firmware itself) or a good workaround. If some
python master out there comes up with a fix, I would be very, very happy to get
it. Thanks!
The Synchronized Motor support has not been extensively tested for accuracy.
It seems to mostly work well but the accuracy of the braking function and the
closeness of the two motors to each other have not been assesed.
Support for a number of sensors has not been tested at all, due to lack of
hardware. I have started a project to test this code, but the going is slow
and I have decided to go ahead and release rather than waiting several more
months. If you have a problem with a digital sensor, see the troubleshooting
guide below and don't forget to report your trouble!
NXT-Python has not been tested and may not work with custom nxt firmware
versions (if you don't know what that means, you don't need to worry about it).
However, if the firmware uses the standard USB/BT communications protocol,
everything should more or less work. NXT-Python has been tested with bricks
using firmware version up to 1.29 and is compatible with protocol version 1.124
(used by most if not all of the official firmwares).
-=-=-If you co'd the SVN...-=-=-
The Arduino directory of an svn checkout (not included with release
packages) contains a digital sensor unit test system called nxtduemu. It is
intended for developers and advanced users who are looking to experiment with
sensors and the digital sensor framework and classes. See Arduino/README for
more info and usage instructions.

Specific Stability Status:
nxt.brick, nxt.telegram,, and nxt.system:
Hardly changed since NXT_Python; very, very stable.
USB Communication System (nxt.usbsock)
On Linux: Very stable and extensively tested.
On Windows: Somewhat tested; seems to work pretty well.
On Mac: Should be working, though I have not heard either way.
BlueTooth Communication System (nxt.bluesock, nxt.lightblueglue)
On Linux: Stable; well tested.
On Windows: Stable; working last I checked.
On Mac: Reported working.
Stable, well tested.
Stable except for Synchronized Motor support, which is experimental at
this stage and has not been extensively tested.
Code not specific to a particular sensor is well tested and working
well. About half of the sensor classes were last reported working; the
rest have not to my knowlege been tested and were written blindly from
the manuacturers' specifications.
If there's a problem with this one, I'm gonna cry.


NXT-Python's Head Developer:
Marcus Wanner (
The support and development mailing list:
Report bugs and suggest new features at:

Thanks to:

Doug Lau for writing NXT_Python, our starting point.
rhn for creating what would become v2, making lots of smaller changes, and
reviewing tons of code. (esp. Ryan Kneip) for helping out with the code for a lot of
their sensors and expanding the sensors covered by the type checking
HiTechnic for providing identification information for their sensors. I note
that they have now included this information in their website. ;)
Linus Atorf, Samuel Leeman-Munk, melducky, Simon Levy, Steve Castellotti,
Paulo Vieira, and anyone else I forgot for various fixes and additions.
All our users for their interest and support!

Troubleshooting Digital Sensors (don't read unless you have problems):
If you are getting errors, strange behavor, or incorrect values from a digital
sensor, chances are that there is a bug in our code. Follow these instructions
to try and find out what's wrong:
1. Test the sensor with a different access library to make sure it's working
2. Check your code again. There are some weird "features" in the interfaces
of some of the sensors; make sure you are doing things right.
3. Locate the sensor class's source code in nxt-python. It should be
somewhere in nxt/sensor/<manufacturer>.py, under the heading "class SensorName(
BaseDigitalSensor):". Read any comments for instructions on certain things.

If you get to here and are still having a problem, you can either go ahead and
report it now or continue to try and find and fix the problem and then report
it (or not report it at all, but that wouldn't be very nice...).
Python experience required beyond this point.

4. Get the sensor's specifications from the manufacturer's website. Make
sure it includes a table of I2C registers and instructions for using them.
5. Pick one of the following depending on what the problem is:
Cause: We screwed up.
Solution: Check the line mentioned in the error for incorrect syntax or
other problem. A bit

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