Lego Mindstorms

The LEGO Mindstorm series of kits contain software and hardware to create small, customizable and programmable robots. They include a programmable 'Brick' computer that controls the system, a set of modular sensors and motors, and LEGO parts from the Technics line to create the mechanical systems.

The hardware and software roots of the Mindstorms Robotics Invention System kit go back to the programmable brick created at the MIT Media Lab. This brick was programmed in Brick Logo. The first visual programming environment was called LEGOsheets,^[1] since it was created by the University of Colorado in 1994 based on AgentSheets.

The original Mindstorms Robotics Invention System kit contained two motors, two touch sensors, and one light sensor. The NXT version has three servo motors and one light, sound, and distance as well as 1 touch sensor. The NXT 2.0 has 2 touch sensors as well as a light and distance sensor, and support for 4 without using a sensor multiplexor. Lego Mindstorms may be used to build a model of an embedded system with computer-controlled electromechanical parts. Many kinds of real-life embedded systems, from elevator controllers to industrial robots, may be modelled using Mindstorms.

Mindstorms kits are also sold and used as an educational tool, originally through a partnership between Lego and the MIT Media Laboratory.^[2][3] The educational version of the products is called Lego Mindstorms for Schools, and comes with the ROBOLAB GUI-based programming software, developed at Tufts University^[4] using the National Instruments LabVIEW as an engine. In addition, the shipped software can be replaced with third party firmware and/or programming languages, including some of the most popular ones used by professionals in the embedded systems industry, like Java and C. The only difference between the educational series, known as the "Challenge Set", and the consumer series, known as the "Inventor Set", is that it includes another light sensor and several more gearing options.

Mindstorms is named after the book Mindstorms: Children, Computers, and Powerful Ideas by Seymour Papert.^[5]

Robotics Invention System

RCX

First-generation RCX programmable brick.

The first generation of Lego Mindstorms was built around a brick known as the RCX (Robotic Command eXplorer). It contains a 8-bit Renesas (Then a part of Hitachi) H8/300 microcontroller as its internal CPU. It also contains 32K of RAM that stores the firmware and user programs. The brick is programmed by uploading a program (written in one of several available programming languages) from a Windows or Mac computer to the brick's RAM via a special infrared (IR) interface. After the user starts a program, an RCX-enabled Mindstorms creation may function totally on its own, acting on internal and external stimuli according to the programmed instructions. Also, two or several more RCX bricks can communicate with each other through the IR interface, enabling inter-brick cooperation or competition. In addition to the IR port, there are three sensor input ports and three motor output ports (also usable for lamps, etc.). There is also an LCD that can display the battery level, the status of the input/output ports, which program is selected or running, and other information.

Version 1.0 RCX bricks feature a power adapter jack to allow continuous operation instead of the limited operation time when using batteries. In version 2.0 (as well as later 1.0s included in the RIS 1.5), the power adapter jack was removed. Power adapterpped RCX bricks are popular for stationary robotics projects (such as robot arms) or for controlling Lego model trains. In the latter context, the RCX needs to be programmed with Digital Command Control (DCC) software to operate multiple wired trains.

The IR interface on the RCX is able to communicate with Spybots, Scout Bricks, Lego Train, and the NXT (using a third-party infrared link sensor.) The RCX 1.0 IR receiver carrier frequency is 38.5 kHz, while the RCX 2.0 IR carrier frequency is 76 kHz. Both versions can transmit on either frequency.^[6] The carrier signal is generated by one of the RCX's internal timers. The RCX communicates with a computer using a Serial or USB IR tower. The tower is supported by Windows 98, Me, and XP (32-bit). A patch is available for hyper-threading/multi-core CPUs. There is no formal support for Windows Vista (32-bit), but there are reports of correct functionality. The USB tower does not work on a 64-bit OS unless a 32-bit OS is used in conjunction with a virtual machine. The serial tower works normally under 64-bit Windows 7 using a third-party USB-to-serial adapter.

All versions of the RCX have a unique number printed on it, necessary for technical support and used as the ID number of the RCX for your Lego Mindstorms account on the now-defunct Lego Mindstorms RCX website. The first RCX produced is marked "000001" and was on display at the Mindstorms 10th Anniversary event.^[7]

Programming languages

Lego Mindstorms' programming is command box programming, rather than code programming.

Lego-supplied languages:

• RCX Code (included in the Mindstorms consumer version sold at toystores)
• ROBOLAB (based on LabVIEW and developed at Tufts University)

Popular third-party languages:

• GNAT GPL Allows programming NXT using the Ada language for real-time and embedded programming.
• Ch interpreter, cross-platform C/C++ interpreter
• Ch Mindstorms NXT Control Package
• C and C++, under brickOS, formerly LegOS
• C and Assembly, under the GCC open source firmware kit NXTGCC
• Interactive C, C-like language used in robotics competitions
• Java, under leJOS or TinyVM
• Not eXactly C, an open source C-like high-level programming language, download compiler from http://bricxcc.sourceforge.net/nxc/
• Not Quite C (NQC)
• pbFORTH, extensions to Forth
• pbLua, version of Lua
• Visual Basic, via the COM+ interface supplied on the CD

Lego camera

The Lego camera on its own is technically not a robotic toy; rather, it is a normal webcam (a Logitech QuickCam Web) packaged into a Lego shell. Being a normal webcam, the Lego Camera is, unlike most Mindstorms products, not programmable and is only usable connected to a PC or some other device that supports USB webcams.

The Lego camera is meant to be used with the included Vision Command software which can also interface with an RCX and thus enables creating robots with "vision". The software is capable of detecting different lightings, motion, and colors. It can also be used with any other software that uses a webcam. The webcam is capable of recording up to 30 frames per second. It also contains a microphone to record sound for videos.

4.5V PC interface

The very first programmable Lego product (1989). It came with a dedicated IBM-PC-compatible ISA interface card, a ribbon cable, and a control panel. The control panel included six non-reversible 4.5V output ports, three reversible 4.5V output ports (each using the power lines from their two adjacent non-reservible ports), two 4.5V input ports, and one continuous 4.5V output port. It also features a manual-override stop-button. Using programs running on the host computer, the user could create stationary programmable robotic Lego inventions using the older 4.5V system. The 4.5V PC Interface was superseded by the 9V-based Dacta Control Lab in 1995.

Technic control center

The Lego Technic control center (1990) was the first programmable standalone Lego product, by the sense of being able to store sequence-based programs and run them. It featured three output ports and manual control, and it was only capable of storing linear sequences of manual input plus timing information. It could store up to two programs at once.

The manual controls could be used to independently control the three motors. To record a program; the controller had to be put in programming mode, and then any manual cotrol would be recorded to the program. Pauses could also be included in a program. When the recording was done, the controller could successfully recall and execute any manual action done during the recording. The executing program could be set to loop infinitely.

Compared to the later programmable controllers, the Technic control center is extremely simple and can only barely be called programmable.

Dacta control lab

Being released in 1995; the Dacta Control Lab was the very first Lego product to feature the sensors used in later 9V-based automated Lego products. The control lab was a datalogger which featured four passive input ports, four active input ports, eight controllable 9V output ports and one continuous output port. It also featured a manual-override stop-button. The control panel connected to a computer using a serial-port with a specially designed adapter cable, and a supplied computer-program allowed the user to conditionally program the outputs. This allowed for robotic operation of mostly stationary Lego inventions. The Control Lab superseded the old 4.5V PC interface from 1989, which was the first fully programmable Lego interface.

The connectors of the early sensors were color-coded according to their type. Active sensors had blue connectors and Passive sensors had yellow connectors. Later Pbricks kept the color-coding for the input ports, but the later sensors dropped the color coding of the connectors (using black connectors instead). The early touch-sensors were also of a different kind and shape compared to the later touch-sensors. Most notably; instead of featuring a removable cable, the cable was fixed just like the other sensors. These early sensors also featured longer cables than their more recent counterparts.

The Control Lab was designed for schools and educational use, and was as a result not available to the mass market. It was later replaced by the RCX and the educational release of the Robot Invention System which allowed for mobile inventions in addition to stationary inventions.

Cybermaster

Lego Cybermaster

Cybermaster was mainly sold in Europe and Australia/New Zealand, but was available for a short time in America via the Lego Club magazines. It was aimed at a younger audience as an early attempt of merging computer gaming with robotics and Lego. The Pbrick shares many, especially software, features with the RCX but differs in appearance and technical specifications: 1 output (plus 2 built-in) and 3 sensors.

• It uses RF (27 MHz R/C band) instead of IR for communication.
• It has two built-in motors with integrated tachometers and speedometers.
• It is limited to passive sensors (a simple A/D with internal pull-up resistors).
• The sensors shipped with it are color coded and have internal resistors in their open state (allowing the Pbrick to sense which sensor is attached to which port).
• It has a fixed firmware (so it cannot be upgraded or replaced).
• It has limited RAM for programs and only one program slot.

Despite its obvious limitations it has a number of advantages over its 'big brother', the RCX.

• The RF link has greater range and is omnidirectional.
• The built-in tachometer and speedometer sensors on the internal motors provides the same function as the external rotation sensor to the RCX, but without using up sensor ports.

This makes it very useful for various mobile platforms and performing basic motion/positioning tasks.

It talks the same protocol as the RCX but cannot communicate directly to it (due to IR vs RF) but with a repeater (a computer with 2 serial ports and a simple program) they can be integrated.

Codepilot

Sold as part of the Barcode Truck kit. This unit was the first programmable brick (or Pbrick). It features a single motor, a single touch sensor and a light sensor. It is programmed by setting it to 'learn' and using the light sensor to feed barcoded commands. The command set is very limited. Since barcode is just a series of variances in light, this form of command entry was dubbed VLL (Visual Light Link) and has been used in several later Lego models.

Scout

Lego also released a blue computer called the Scout, which has 2 sensor ports, 2 motor ports (plus one extra if linked with a Micro Scout using a fiber optic cable), and a built in light sensor, but no PC interface. It comes with the Robotics Discovery Set. The Scout can be programmed from a collection of built-in program combinations. In order to program the Scout, a user must enable "power mode" on it. The Scout can store one program.

The Scout is based on a Toshiba microcontroller with 32KB of ROM and 1KB of RAM, where about 400 bytes are available for user-programs. Due to the extremely limited amount of RAM, many predefined subroutines were provided in ROM. The Scout only supports passive external sensors, which means that only touch, temperature and other unpowered sensors can be used. The Analog-to-Digital Converters used in the Scout does only have a resolution of 8 bits in contrast to the 10-bit converters of the RCX.^[8]

There was a plan for Lego to create a booster set that allows you to program the Scout from a computer with a software such as RCX code. However, due to the complexity of this project, it was abandoned.

The RCX can control the Scout brick using the "Send IR Message" program block. The RCX does all of the controlling, and therefore can be programmed with the PC, while the Scout accepts commands. The Scout brick must have all of its options set to "off".

The Scout is also capable of using VLL to control a Micro Scout.

Micro Scout

The Micro Scout was added as an entry level to Lego robotics. It is a very limited Pbrick with a single built-in light sensor and a single built-in motor. It has seven built-in programs and can be controlled by a Scout, Spybotics or RCX unit using VLL. Like the Scout, the Micro Scout is also based on a microcontroller from Toshiba.

The unit was sold as part of the Droid Developer Kit (featuring R2D2) and later the Darkside Developer Kit (featuring an AT-AT Imperial Walker).

Spybotics

Main article: Lego Spybotics

Spybotics is a robotics package. It consists of four colour-coded robots called Spybots, a programming language with which to control the Spybots, and ten simulated missions.

Lego Mindstorms NXT

Main article: Lego Mindstorms NXT

Lego Mindstorms NXT is a programmable robotics kit released by Lego in July 2006, replacing the first-generation LEGO Mindstorms kit.^[9] The kit consists of 577 pieces, including: 3 servo motors, 4 sensors (ultrasonic, sound, touch, and light), 7 connection cables, a USB interface cable, and the NXT Intelligent Brick. The Intelligent Brick is the "brain" of a Mindstorms machine. It lets the robot autonomously perform different operations. The kit also includes NXT-G, a graphical programming environment that enables the creation and downloading of programs to the NXT. The software also has instructions for 4 robots; Alpha-Rex (a humanoid),Tri-Bot (a car), Robo-Arm T-56 (a robotic arm), and Spike (a scorpion)

LEGO MINDSTORMS NXT Educational Version

This is the educational version of the NXT set from LEGO Education, which is made for school use. Software is sold separately, and the Education Resource Set for the best use. It includes a light sensor, a ultrasonic sensor, a sound sensor, three lamps and a pair of touch sensors. The first set consists of about 400 pieces, and the extra set consists of about 600 pieces. The Education Version is most suited for those who have older versions of MINDSTORMS sets around, mostly thanks to its 3 converter cables. It costs about US$410.00 with the Bluetooth Dongle.

Lego Mindstorms NXT 2.0

Main article: Lego Mindstorms NXT 2.0

The Lego Mindstorms NXT 2.0 was launched on 5 August 2009. It contains 619 pieces (includes sensors and motors), the new Color Sensor, two Touch Sensors and an Ultrasonic Sensor. The NXT 2.0 uses Floating Point operations whereas earlier versions uses Integer operation.^[10] The kit costs around USD 280.

Mindstorms Color Sensor.

Programming languages

Further information: Lego Mindstorms NXT#Programming

Name	Language type(s)	Notes	URL
Actor-Lab	Custom flowchart-like language		[1]
Ada	Ada	Requires nxtOSEK	[2]
Ada Interface to MindStorms	Ada		[3]
brickOS	C/C++		[4]
Ch	C/C++ Interpreter	Control Lego Mindstorm in C/C++ interactively without compilation	[5]
Enchanting	Drag and drop, similar to NXT-G	Program your robots simply by dragging the line of functions.	[6]
FLL NXT Navigation	Uses NXT-G and .txt files		http://fllnxtnavigation.codeplex.com/ FLL NXT Navigation
GCC	C/C++, Objective-C, Fortran, Java, Ada, others		[7], [8]
GNU Toolchain for h8300	C/C++, ASM		[9]
jaraco.nxt	Python	Python modules providing low-level interfaces for controlling a Lego NXT brick via Bluetooth. Also includes code for controlling motors with an Xbox 360 controller using pyglet.	[10][11]
LabVIEW	National Instruments LabVIEW visual programming language (G code)	Core language used to develop Mindstorms NXT software. Can use available add-on kit to create and download programs to NXT, create original NXT blocks or control robot directly via USB or Bluetooth using NXT fantom.dll	[11]
Lego.NET	Anything that can compile to CIL, works best with C#	Does not come with a compiler, converts CIL to machine code	[12]
Lego::NXT	Perl	Set of Perl modules providing real-time low-level control of a Lego NXT brick over Bluetooth.	[13] [14]
LegoNXTRemote	Objective-C	Remote control program for remotely operating and programming a Lego NXT Brick. Supports NXT 2.0 and 1.0, sensors, all 3 motors, automatic "steering" control, and running preloaded programs.	[15]
leJOS	Java	A java based system for advanced programmers can handle most sensors and things like GPS, speech recognition and mapping technology. Can be interfaced with the Eclipse IDE or run from the command line	[16]
NXTGCC	Assembly, C, makefiles, Eclipse, etc.	The first GCC toolchain for programming the Lego Mindstorms NXT firmware.	[17]
nxtOSEK	C/C++		[18]
librcx	C/C++	A library for GCC	[19]
Logitech SDK	Visual Basic, Visual C++	Can be combined with an RCX control library such as spirit.ocx from the MindStorms SDK to make use of the Lego Cam	[20][dead link]
MicroWorlds EX Robotics Edition		This is a program in the MicroWorlds series that allows students to control the NXT.	[21]
NQC	NQC, a C-like language		[22]
NXT++	C++	Allows controlling the NXT directly from any C++ program, in Visual Studio, Windows.	[23]
NXT_Python	Python	NXT_Python is a package for controlling a LEGO NXT robot using the Python language. It can communicate via USB or Bluetooth.	[24]
NXT-Python	Python	Based on NXT_Python, includes additional advanced features, support for around 30 sensors, and multiple brick connection backends. Works on Windows, Linux, Mac.	[25]
Lestat	C++	Allows you to control the NXT directly from any C++ program in Linux.	[26]
OCaml Mindstorm	Objective Caml	Module to control LEGO NXT robots using OCaml through the Bluetooth and USB interfaces.	[27]
Mindstorms SDK	Visual Basic, Visual C++, MindScript, LASM	You do not need VB to use the VB features as MS Office comes with a cut down version of VB for making macros	[28] Unofficial Site. The LEGO Company no longer offers technical support to advanced users on the historical MINDSTORMS range, specifically those using the SDK 2.5 (RCX and Scout), and Spybotics range. Related tools and documentation were removed from the Official LEGO MINDSTORMS website in 2008.
OnScreen	A custom language which can be programmed directly on the RCX		[29]
pbForth	Forth		[30]
PBrickDev	PBrickDev, a flowchart based language.	Has more functionality than the RIS language, such as datalogs and subroutines/multithreading.	[31]
PRO-BOT	A kind of Visual Basic/spirit.ocx-based language	Designed for robots which are in contact with the workstation at all times	[32]
QuiteC	C	A library for use with GCC and comes with GCC for Windows.	[33]
RCX Code	RCX Code, a custom flowchart-based language	Included in the Mindstorms consumer version sold at toystore	[34][dead link]
ROBOLAB	A flowchart language based on LabVIEW	This is the programming environment offered to schools who use MindStorms, supports the Lego Cam	[35]
RoboRealm	A multi-platform language that works with IRobot Roomba, NXT, RCX, VEX, and many other popular robotic sets. This language is also capable for video processing using a webcam, this gives your robot excellent vision since it can filter out certain colors, lock-on to a certain area of color, display variables from the robot or computer, and much more. The software works with keyboard, joystick, and mouse.		[36]
Robotc	A multi-platform C language designed for users needing powerful debugging tools for the NXT, RCX, VEX, and soon-to-be FIRST Controller (for FRC).	ROBOTC gives the ability to use a text-based language based on the C language. It includes built-in debugger tools, as well as (but not limited to) code templates, Math/Trig operations (sin, cos,tan, asin,acos... etc.), user-friendly auto-complete function built into the interface, built-in sample programs	[37]
ROS	A Linux based library for writing robots. The stack "nxt" provides interface with the NXT.		[38]
Robotics.NXT	Haskell	A Haskell interface over Bluetooth. It supports direct commands, messages and many sensors (also unofficial). It has also support for a simple message-based control of a NXT brick via remotely executed program (basic NXC code included).	[39]
ruby-nxt	Ruby	Provides low-level access to the NXT via Bluetooth as well as some preliminary high-level functionality.	[40]
RWTH – Mindstorms NXT Toolbox	MATLAB	Interface to control the NXT from MATLAB via Bluetooth or USB (open-source).	[41]
SqLego	Squeak		[42]
TclRCX	Tcl		[43]
Terrapin Logo	LOGO		[44]
TinySoar	Soar	An implementation of the Soar artificial intelligence architecture that runs on the RCX brick. Soar incorporates acting, planning, and learning in a rule-based framework.	[45]
TinyVM	Java	A predecessor to the lejos language. An open source Java based replacement firmware for the Lego Mindstorms RCX microcontroller.	[46]
The Transterpreter	Occam		[47]
TuxMinds	(Linux) GUI for various distributions, an open source IDE based on Qt. Supports a lot of bots. RcX, NxT and Asuro are predefined.	With the XML-based configuration file almost any kind of bot (or microcontroller) can be added. Own equipment can be added in the same manner.	[48]
Gostai URBI for Lego Mindstorms NXT	URBI, C++, Java, Matlab	Easy to use parallel and event-driven script language with a component architecture and opensource interfaces to many programming languages. It also offers voice/speech recognition/synthesis, face recognition/detection, Simultaneous localization and mapping, etc.	[49]
Vision Command	RCX Code	The official programming language for use with the Lego Cam, that allows you to control your robot with color, motion, and flashes of light.	[50][dead link]
XS	Lisp		[51]
LegoLog	Prolog	Uses an NQC program to interpret commands send from the PC running the Prolog code	[52]
Microsoft Visual Programming Language (VPL)	Graphical flowchart, based on .NET	With the Microsoft Robotics Studio, it uses a native NXT program msrs to send and receive messages to and from a controlling program on a computer via Bluetooth	[53]
DialogOS	Graphical Flowchart for voice controlled robots	DialogOS combines speech recognition and speech synthesis with robotics, enabling you to build talking robots that react to your voice commands.	[54]
Processing	Java (Simplified / programmed C-style)	Processing (programming language) is an open source programming language and environment for people who want to program images, animation, and interactions. It is used by students, artists, designers, researchers, and hobbyists for learning, prototyping, and production. To control the NXT with Processing you can use the NXTComm Processing library developed by Jorge Cardoso.	[55],[12]
Interactive C	C-style language.	Language developed for the MIT Lego Robot Design Contest	[56]
pbLua	API for the Lua programming language for the Mindstorms NXT, text-based	pBLua: ... is written in portable C, with minimal runtime requirements; can be compiled on the fly on NXT; is a small, easy to read, and easy to write language; has extensive documentation available online and in dead-tree format, and a very friendly newsgroup	pbLua, Lua.org

Community

There is a strong community of professionals and hobbyists of all ages involved in the sharing of designs, programming techniques, creating third-party software and hardware, and contributing of other ideas associated with Lego Mindstorms. The Lego Mindstorms system/website is organized much like a wiki, harnessing the creative potential and collaborative efforts of participants. Lego also encourages sharing and peering by making software code available for downloading and by holding various contests and events.

See also

	Lego portal
	Robotics portal

• Open Blocks
• FIRST Lego League
• RoboCup Junior
• Dexter Industries – Sensors for the LEGO MINDSTORMS NXT.
• Vex Robotics Design System
• Big Trak
• iRobot Create
• LabVIEW
• Robofest
• Robotis Bioloid
• Actor Lab
• The Robotic Workshop
• URBI
• Lego Logo, an earlier use of Lego bricks with computer control.
• Robotics suite

Notes

1. ^ "LEGOsheets". LEGOgang. http://l3d.cs.colorado.edu/systems/legosheets/Home.html. Retrieved 3 December 2008. 
2. ^ http://lcs.www.media.mit.edu/groups/el/projects/programmable-brick/^{[dead link]}
3. ^ "Programmable Bricks". Projects. MIT Media Lab. http://llk.media.mit.edu/projects.php?id=135. Retrieved 3 December 2008. 
4. ^ http://www.ceeo.tufts.edu/^{[dead link]}
5. ^ The Origins of Mindstorms from Wired
6. ^ http://osdir.com/ml/hardware.lego.robotics/2007-08/msg00017.html
7. ^ http://flickr.com/photos/brickjournal/3079324996/in/set-72157610670686416/
8. ^ http://web.archive.org/web/20010210104326/http://mindstorms.lego.com/products/rds/hackers.asp
9. ^ "What’s NXT? LEGO Group Unveils LEGO MINDSTORMS NXT Robotics Toolset at Consumer Electronics Show". Press Release. LAS VEGAS: LEGO Company. 4 January 2006. http://www.lego.com/eng/info/default.asp?page=pressdetail&contentid=17278&countrycode=2057&yearcode=&archive=false. Retrieved 3 December 2008. 
10. ^ "Lego Robotics FAQ". 2009. http://www.lego.com/education/school/default.asp?locale=2057&pagename=fqnxt&l2id=3_2&l3id=3_2_5&l4id=3_2_5_1#h. Retrieved 2 March 2010. 
11. ^ "jaraco.nxt Download". jaraco.com. http://www.jaraco.com/projects/jaraco.nxt. Retrieved 3 December 2008. 
12. ^ "nxt sensor value viewer". Diegobaca.co.uk. http://www.diegobaca.co.uk/NXT/nxt.html. Retrieved 3 December 2008. 

References

• Bagnall, Brian. Maximum LEGO NXT: Building Robots with Java Brains Variant Press. 2007. ISBN 0-9738649-1-5
• Bagnall, Brian. Core LEGO Mindstorms Prentice-Hall PTR. 2002. ISBN 0-13-009364-5
• Baum, Dave. Definitive Guide to LEGO MINDSTORMS, 2nd ed. Apress. 2002. ISBN 1-59059-063-5.
• Erwin, Benjamin. Creative Projects with LEGO Mindstorms (book and CD-ROM). Addison-Wesley. 2001. ISBN 0-201-70895-7.
• Ferrari et al. Building Robots with LEGO Mindstorms: The Ultimate Tool for Mindstorms Maniacs. Syngress. 2001. ISBN 1-928994-67-9.
• Gindling, J., A. Ioannidou, J. Loh, O. Lokkebo, and A. Repenning., "LEGOsheets: A Rule-Based Programming, Simulation and Manipulation Environment for the LEGO Programmable Brick," Proceeding of Visual Languages, Darmstadt, Germany, IEEE Computer Society Press, 1995, pp. 172–179.
• Breña Moral, Juan Antonio. Develop LeJOS programs Step by Step, "http://www.juanantonio.info/lejos-ebook/

External links

• Official Lego Mindstorms (NXT)
• LEGOsheets
• Lego Mindstorms at the Open Directory Project
• A NXT 2.0 robot in action
• Lego Mindstorms robot solving the Rubik's Cube in 12 seconds
• "Tetrisbot", a Lego Mindstorms robot that plays Tetris