Robotics

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Robotics

• Bluetooth Communications
• Brain storm project ideasProgramming
  considerationsHomework
• Library project presentations.Prepare to present
  proposal for building project

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General communications

• Protocols (Bluetooth is a protocol) work in
  specific ways
• handshaking, polling, timing
• Messages may not get through
• BT checks for messages of a certain data type
• .

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Good news

• Bluetooth is the protocol for many gadgets,
  including cell phones.
• Not all BT are the same
• Some PC dongles work with NXT and some do not!
• nxtasy.org and other on-line groups are very
  responsive
• I posed a problem and get responses
• One person said it couldnt be done
• Another (Brian Davis) produced an example that
  (according to him) works 80 of the time.

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General NXT-G

• To get data wires into a switch clause, need to
  UNCLICK the flat view
• Getting (sharing) other .rbt files is possible,
  though tricky
• Used Brians GetKey
• NOTE this was just to test his code. Your
  application need not use this.

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Master echo idea

• Problem how to communicate one slave to another
  slave
• Solution slave sends message to the masters
  mailbox 1, 2, 3. The master passes it on to
  connection 1, 2, or 3.

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Slave echo (test)

• Note this program, running on all 3 slave
  robots, is just to test the concept and along
  the way demonstrates several (new to us) NXT-G
  features
• Random number generated to be sent
• Concatenation of text
• Operator presses 1 of 3 NXT buttons. This
  determines the target slave.
• Recipient (of passed on message) makes beep and
  displays message received.

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More NXT-G

• Makes use of Display mini-blocks
• There also are motor and move mini-blocks.
• Mini-blocks were/are more efficient versions of
  original blocks.
• Should be present on the class Mindstorms.
• If you have your own system, need to follow
  directions to download program for adding blocks
  AND this particular set.

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masterecho.rbt
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slaveecho.rbt
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Caution

• The parallel threads may be problematic.
• NOTE the busy-wait for message does cause action
  on both the master and the slaves according to
  information on-line

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Programming Process

• Make small testing programs
• The slaveecho program may be bigger than an
  actual use of relaying messages
• Use sounds and displays
• Using the NXT buttons for events as opposed to
  bumper or other sensors may be good for debugging
  process

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Programming

• Use MyBlocks the one great idea of programming
  is the concept of subroutine.
• Write comments in NXT-G files
• Plan / Diagram
• Especially events triggering multi-robot action
• Memory is limited!
• Remove unnecessary files. This may include sound
  files used in debugging.
• Look for use of move vs motor vs mini-blocks.
• Next class

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MyBlock

• programs must be stored in MyBlock folder on
  computer running Mindstorms
• Global variables (variables shared by calling
  program and the MyBlock) must be defined in both
• MyBlock can have 0, 1 or more inputs and 0, 1 or
  more outputs, but these must be set up in
  original definition.
• This may lead you to use global variables!

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Building project Requirements

• Make use of at least 2 if not more sensors
• Cause change in the environment
• This could be making another robot move
• Can build new robot.
• NOTE the base robot is called the Tribot
• Can use on-line directions
• Can use on-line programs BUT need to another them
• Can be teams
• Can be multiple robots (rather, multiple NXT
  bricks)

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Requirements

• Present proposal
• Final project
• Demonstrate
• 1 page summary, including pictures and/or
  diagrams
• NXT-G code must contain comments
• NXT-G code must have MyBlocks

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Ideas?

• www.nxtasy.com (see also the projects archive)
• has several project ideas, including
• Maze
• Going into 'building' and finding something

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Ideas?

• mindstorms.lego.com/nxtlog
• Many projects, with photos and code
• You must understand the code as well as the
  rationale in the physical design.
• EXTRA credit for any accepted project.
• (Yes, I will change a grade if this happens after
  grades are submitted.)

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Homework

• Postings
• Prepare proposal for building project 4/17
• Projects presented 5/5