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Robot Programming Tips

• Week 4 Day 2
• By Matt Gates and James Beams
• FEH Class of 1999

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Robot Programming Tips
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Limitations of the Handy Board

• Limited memory (16K available for program code)
• Limited CPU speed
• Very slow floating point calculations (no
  floating point hardware)
• Limited I/O (LCD screen, 7 analog, 8 digital
  ports)
• Strategy Code must be small, fast, and make
  efficient use of the resources you have.

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Limitations of the System

• Controlling a mechanical system is much different
  than controlling a computer!
• Why? System will never run the same way twice!
• System runs in real time, independent of your
  program.
• You must constantly monitor the system and ensure
  that what you want to happen is actually
  happening.
• Test, test, and test some more!!!

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Strategies I What NOT To Do

• DO NOT write one large main ( )
• DO NOT write code without error checking
• DO NOT assume your code will work right
• DO NOT use lots of memory or complex algorithms
• DO NOT wait until the last minute to test your
  code

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Strategies II Maintainable Code

• Break your code into small segments (functions)
  that perform specific, simple tasks.
• Example motors_half_speed ( )
• Use symbolic constants (define) instead of
  literals.
• motor (LEFT_SIDE, FULL_POWER)
• NOT motor (1, 100)
• Makes it easier to update your code if you make
  changes to the robot design or your goals.

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Strategies III Getting Around

• The most difficult part of your task will be
  getting from Point A to Point B.
• Driving straight
• Turning
• Avoiding obstacles

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Strategies III Getting Around

• You should spend time developing and testing a
  routine that allows you to move around reliably.
• Use shaft encoder data to keep wheels _at_ same RPM.
• Shaft encoders can also help in turning.
• Have adequate bump sensors and intelligent
  responses.

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Pseudo code Example 1

• The following pseudo code example is for a
  drive_straight function for a specific distance
  to be traveled and which corrects for uneven
  motor speeds.

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Strategies IV Break up Course

• The course can be handled more easily if you
  break it up into sections or tasks.
• Ex Determine object values, navigate to and pick
  up object, navigate and drop off object.
• Write code to handle each section separately.
• Now you can test parts of the course
  individually.
• Use the knob to select what section of code to
  execute.

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Pseudo code Example 2

• The following pseudo code example breaks the
  course (for that year) into six routines.

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Strategies V Multithreading

• IC can run more than one functional thread at
  once.
• Useful to perform background monitoring while
  doing main tasks.
• Ex Run drive straight code to make corrections
  to motor power while driving.

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Strategies V Multithreading

• The more threads running, the more CPU resources
  used.
• Can hurt IR reception, shaft encoder counts, etc.
• Should keep number of threads small.
• See IC documentation on start_process ( ) for
  more info.

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Strategies VI Testing

• Thorough testing is essential!
• Tips
• Begin by testing individual course sections, then
  combine until you can do the whole course.
• Use the LCD screen to output useful values (ex.
  shaft encoder ticks, motor power, course side, IR
  output).
• Make sure your robot will work even if the
  battery charge is low.
• Dont stop testing until the competition is over!

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Grade Sheet for Pseudo Code / Flow Chart