OGEL: LEGO Mindstorm Controller Language

1
OGELLEGO Mindstorm Controller Language

• Michael Ching
• Gerardo Flores
• Matt Kalish
• Charles ODonnell
• 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

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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

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OGEL (Contd)

• 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

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Architecture
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Architecture Discussion

• 5 Stages Preprocessor, Lexer/Parser,
  Static-Semantic Checking, UNI-OGEL Generator,
  Architectural Translator.
• Preprocessor include, define, task/function
  order independence

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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

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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 (hitgt0) 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 gt 0) catch done reverse()
task main() rcx demo first_born
first_born.addTask(rev_task)
first_born.addTask(go)
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Watch This Puppy run!

• Division of Work
• Front-End Michael Ching / Gerardo Flores
• Back-End Charles ODonnell
• Floater, Docs Compilation Matt Kalish