Introduction to Lego Mindstorms LMICSE Workshop June , 2005 Alma College

The Lego Mindstorms Kit The RCX (the brains) Two Geared Motors Two Touch Sensors One Light Sensor A USB IR Tower A CD-ROM The Constructopedia Lots of Lego Pieces! RCX Brick and Standard Sensors and Motors

A Basic Robot Design The Constructopedia is a building guide. Shown at left is the basic Roverbot from the Constructopedia A robust design Allows attachment of any of double bumper (shown) wheel sets (shown) single bumper light sensor tank like treads A recommended design starting point Basic Roverbot Configuration

The RCX Itself (1) Hitachi H8 series microcontroller 8 bit CPU at 16 MHz 32 KByte RAM 16 KByte ROM for the BIOS Serial I/O (input/output) ADC (analog digital converter) Built-in timers RCX Brick

The RCX Itself (2) Liquid crystal display (LCD) Four push buttons One small internal speaker Three sensor inputs Three motor outputs One infrared (IR) interface with a proprietary protocol Requires 6 AA batteries RCX Brick

Actuators With Kit Geared Motors Available From Lego High-speed Motors Mini-motor Light Brick Available third party Servo Motor/Servo Controller Servo Controller w/ 2 Servo Motors Ungeared and Geared Motors

Sensors Basics Mindstorms sensors come in two types Active: RCX supplies power Example: Light sensor (supplied with kit) Passive: RCX just detects changes in resistance Example: Touch sensor (supplied with kit)

Sensors Available from Lego Touch Passive Supplied with Kit Light Active Supplied with Kit Rotation (Angle) Active Add-on Touch, Light and Rotation Sensors

Third Party Sensors (1) The sensor interface is well documented Many sets of building instructions for sensors exist, for example see Michael Gasperi’s website Two commercial suppliers we know of:

Third Party Sensors (2) Sonar (Ultrasonic range) Available both from Mindsensors and Hitechnic Magnetic Compass Sensor Available from Hitechnic Active and Passive Multiplexor Available from Mindsensors And many others Hitechnic Sonar Mindsensors Active Multiplexor Hitechnic Compass

Software Architecture Typical Software Architecture Levels

Software Architecture System ROM Layer Low Level Control Software Allows a second piece of software - the firmware Can be bypassed for direct control of the hardware

Lego Firmware The Lego firmware provides an environment for the execution of programs on the RCX. Must be downloaded (just once) before programming the RCX. Other firmware solutions are available. Lego Firmware v. 2.0 permits 5 separate programs 10 threads 32 global variables 16 local variables per thread Broadcast IR protocol

Alternative Firmware Firmware replacements further push the limits of the RCX Popular replacements are tied to alternative programming environments Examples LejOS (Java) see BrickOS (C/C++) see RCXLisp (Lisp) Part of the LMICSE project See

Programming the RCX Mindstorms ships with its own iconic programming language, but this is a very limited language. So others have developed for the RCX almost all the usual programming languages, including: C C++ Java Ada Lisp Forth Smalltalk

So What Now? Let’s play with some Legos!