1. OGEL: LEGO Mindstorm Controller Language Michael Ching Gerardo Flores Matt Kalish Charles O’Donnell May 13, 2003

2. LEGO Mindstorms  Robotic architecture that allows one to build components from Legos and control sensors and motors from a microcontroller  Complexity of microcontroller can be chosen (Scout, RCX 1.0, RCX 2.0, CyberMaster)  Different development environments may be chosen that vary from a drag and drop approach to a C- syntax based language

3. Not Quite C  Targets experienced programmers  C syntax and semantics  Textual language removes the graphical metaphors that limit the type of programs that may be written  Supported by several IDEs (WinNQC, MacNQC, Visual NQC, NQCEdit, Bricx Command Center)  Not modular in nature  Does not support hierarchy or abstraction of code  Questionable event-based support

4. OGEL  Designed to support the RCX 1.0 but offers support for future firmware (Compatible with 2.0)  Merge desirable characteristics of available technologies  Built scalable hierarchy which improves code reuse

5. OGEL (Cont’d)  Able to create code for multiple target microcontrollers from one file  Improved message passing architecture  Improved modularity which leads to a more stable hierarchy  Allows imbedded self-contained Not Quite C code  Permits separation of RCX, task, message, and function declarations into library files which can be added to any existing code by means of include statements

6. Architecture

7. Architecture Discussion  5 Stages: Preprocessor, Lexer/Parser, Static- Semantic Checking, UNI-OGEL Generator, Architectural Translator.  Preprocessor: #include, #define, task/function order independence

8. Architecture Discussion  Lexer/Parser – Static-Semantic Checking  UNI-OGEL Generator: code duplication & port mapping, source code profiling  Architectural Translator: any architecture, architecture-specific errors discovered (task limit, recursion), optimization

9. Testing  Testing was done in 3 phases Isolated Module Testing Integration Testing Final Testing

10. Sample OGEL Code #define TIME_REV 100 message done; rcx demo { SENSOR_TOUCH hit = $1; left_motor = $A; right_motor = $C; } task go(in hit)(out left_motor, out right_motor) { when (hit>0) do reverse(); nqc.OnFwd(left_motor + right_motor); } void turn()()(out left_motor, out right_motor) { nqc.OnRev(left_motor); nqc.OnFwd(right_motor); nqc.Wait(TIME_REV); nqc.Off(left_motor + right_motor); throw done; } void reverse()()(out left_motor, out right_motor) { nqc.OnRev(left_motor + right_motor); nqc.Wait(TIME_REV); nqc.Off(left_motor + right_motor); turn(); } task rev_task()(out left_motor, out right_motor) { int x = 1; while (x > 0) { catch done; reverse(); } task main() { rcx demo first_born; first_born.addTask(rev_task); first_born.addTask(go); }

11. Watch This Puppy run! Division of Work: Front-End: Michael Ching / Gerardo Flores Back-End: Charles O’Donnell Floater, Docs Compilation: Matt Kalish