Lego Mindstorms

Lego Mindstorms is a line of Lego Group products combining programmable bricks with electric motors, sensors, Lego bricks, and Lego Technic pieces (such as gears, axles, beams, and pneumatic parts) to build robots and other automated or interactive systems.

Lego Mindstorms is marketed commercially as the Robotics Invention System (RIS). It is also sold and used as an educational tool, originally through a partnership between Lego and the MIT Media Laboratory [http://llk.media.mit.edu/projects.php?id=135. The educational version of the products is called Lego Mindstorms for Schools, and comes with the ROBOLAB GUI-based programming software.

Lego Mindstorms may be used to build a model of an embedded system with computer-controlled electromechanical parts. Almost all kinds of real-life embedded systems, from elevator controllers to industrial robots, may be modelled using Mindstorms.

There is a strong community of professionals and hobbyists of all ages involved in the sharing of designs, programming techniques, and other ideas associated with Lego Mindstorms.

The original Mindstorms RCX was released in 1998. In 2006, Lego announced a next-generation Mindstorms system called NXT, centered around a new programmable brick. ^* ^*

RCX

The first generation of Lego Mindstorms was built around a brick known as the RCX. It contains a Renesas H8/300 microcontroller as its internal CPU. The brick is programmed by downloading a program (written in one of several available programming languages) from a PC or Mac to the brick's RAM via a special infrared (IR) interface. After the users 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 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. Power adapter-equipped 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 required for automated model train operation (see References, below, for an example of such software).

Lego also released a brick named the Scout, which has 2 sensor ports, 2 motor ports, a built in light sensor, and no PC interface. The Scout can be programmed, but the user usually selects one of a collection of built-in programs. In order to program the Scout, a user must enable "power mode" on it. The Scout can store one program. 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 acts as a "slave". The Scout brick must have all of its options set to "off". Press run and then send IR codes to it.

RCX/Scout IR Communication Codes

(IR Code/Left/Right)

4/Fwd/Fwd
5/Rev/Rev
6/Fwd/Rev
7/Rev/Fwd
8/Fwd/Off
9/Rev/Off
10/Off/Fwd
11/Off/Rev
12/Off/Off

Available programming languages

Lego-supplied (both of them graphical):

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

Third-party (all of them textual except actor-lab):

C and C++ under BrickOS (formerly LegOS) or using QuiteC
Java under leJOS or TinyVM
Lego.NET
NQC ("Not Quite C")
OnScreen
pbFORTH (extensions to the Forth programming language)
PbrickDev
PRO-BOT
SqLego
TclRCX
Terrapin Logo
Visual Basic
Assembly
XS (a Scheme-like LISP dialect)
actor-lab (http://actor-lab.open.ac.uk) graphic parallel programming language

Lego Mindstorms NXT

The next product in the Mindstorms series is Mindstorms NXT, released in July 2006 ^*. The kit includes three servo motors, a touch sensor, a light sensor (now with the ability to differentiate between colours based on greyscale readings), a new sound sensor, an ultrasonic sensor and a new NXT 'Intelligent Brick'. The kit is sold for $249 USD.

The NXT 'Intelligent Brick' has a 32-bit ARM7 microprocessor (the Lego FAQ website lists the new brick as having a second 8-bit microprocessor with an unnamed architecture), a 60×100 pixel LCD matrix display, USB 2.0 port and Bluetooth wireless connectivity. The ARM7 processor has access to 256 KiB of flash memory and 64 KiB of RAM, whilst the second processor will only have access to (a separate) 4 KiB of flash and 512 bytes of RAM. It has four input and three output ports, though as the connections are digital, it is possible to add Multipacks to extend the amount of sensor and motor ports available. The connector used on I/O sockets is not the same design used on the RCX and use ports similar to an RJ12 connector. Built into the brick itself, there is a loudspeaker with 8 kHz D/A. The brick requires 6 AA type batteries, Alkaline ones are recommended, though it will operate with rechargeable ones.

The Lego Mindstorms NXT Set ships in two versions: The Retail Version and the Education Base Set. The NXT-Brick in the educational version ships with a rechargeable battery and charger. However, this kit doesn't include any programming software which is sold separately (different software licenses: Personal, Classroom, Site).

LEGO has announced that the NXT Intelligent Brick will be released as Open Source and several developer kits will be available containing the brick's interface schematics and driver specifications. ^*

More information can be found on either the Lego Mindstorms website or on the Lego FAQ website.

NXT Brick

32-bit ARM7 main microprocessor
256 KiB flash memory
64 KiB RAM
60×100 pixel LCD matrix display
Can be programmed using a PC or Mac
Users create a program with new software, powered by LabVIEW from National Instruments
A single USB 2.0 port
Bluetooth wireless connectivity, to transfer programs to the NXT wirelessly or offer ways to control robots remotely ( mobile phones and possibly by PDAs)
Digital Wire Interface, allowing for third-party development of external devices

Parts

519 LEGO Technic parts (and Bionicle parts, including Visorak pincers)
Three servo motors, with built-in rotation sensors, and feedback for precise control
Ultrasonic distance and movement sensor
Sound sensor, with sound pattern and tone recognition
Light sensor, detecting different colors and light intensity
Touch sensor (press/release/bump detection)

References

Bagnall, Brian (2002). Core LEGO® Mindstorms Prentice-Hall PTR. ISBN 0130093645
Bagnall, Brian (2007). Maximum LEGO® NXT: Building Robots with Java Brains Variant Press. ISBN 0973864915
Baum, Dave (2002). Definitive Guide to LEGO® MINDSTORMS, 2nd ed. APress. ISBN 1590590635.
Erwin, Benjamin (2001). Creative Projects with LEGO® Mindstorms (book and CD-ROM). Addison-Wesley. ISBN 0201708957.
Ferrari et al. (2001). Building Robots With LEGO® Mindstorms: The Ultimate Tool for Mindstorms Maniacs. Syngress. ISBN 1928994679.