Egr100
Fall 1999
Ileana Streinu
Doreen Weinberger

Topics

• A Tour of Lego MindStorms programming.
  • How it works: multi-tasking versus sequential execution.
  • Individual commands for:
    • Controlling the motors: on/off, direction, power.
    • Sound: beep, tone
    • Counter: reset, add to counter
    • Communication with another RSX: send to RSX, reset message
    • Time: wait, reset timer
  • Watchers: launch a program ("stack") when some event happens. Events are triggered by
    • Sensors: light sensor watcher, touch sensor watcher, etc.
    • Counter: counter watcher. You can do something special when the counter goes beyond a threshold, for instance.
    • Timer: triggers a program when a certain amount of time has passed. Can reset the timer afterwards.
    • RSX: triggers a program when a message has been beamed-off from another RSX. The messages have code numbers. For each code number, or for a group of them, you can have a certain "stack" (program) execute.
  • Main program (stack): other than the watchers, which are triggered by events, you can have something executing all the time (no matter what).
  • Stack Controllers
    They can be used anywhere, either in the main program or in a stack under the control of a sensor watcher.
    • Choose: do one thing or another, depending on whether, at the time the execution of the program gets there, a certain condition is true or false.
    • Repetition: to do things repetitively, either a given number of times, or until a condition happens. Repeat x times, Repeat forever, Repeat while (a sensor condition is true), Wait until (a sensor condition becomes true).
  • My Commands.
    When you want to group things together, for instance some sequence of commands that is done identically in various parts of your program, group them by creating a new command (yours!!). For instance, you can create your piece of music to be played when your robot bumps into a wall, receives a message from another RSX, etc.

• Watch the MIT RoboRats competition (video clip) and some of the students projects
• I will pass around the MindStorms challenges: RoboSports, Extreme Creatures. You can choose some project from the book to do next time. You can use the design in the booklet or improve it, but the programming should be yours!

To do

• Finish the path-following robot using the maze. You might want to stick with a simple mechanical design and check your programming carefully for logical errors. If all looks well, work on calibration.
• Combination of maze path-following with obstacle detection, using bumbers (touch sensors).
• A simple robot communication project: this is essentially a programming exercise (a very useful one). Done by two teams together. One RSX is the master, who sends encoded commands to the slave RSX. When receiving the messages, the slave can do several things (start, stop, sing, etc.).

To turn in