Hey check it out, Make: blogged about CloudSCAD... and of course they spelled my name wrong.  Busier?  People mispronounce my name all the time - it's not BUS-er or B-user or Bus-ay, it's actually Boozer believe it or not.  (yeah yeah I know)  However, this is not the first time it's happened.  A couple years ago the name Tony Burser was immortalized in print when MacTech magazine did a story covering ruby-nxt (a ruby gem I wrote for controlling LEGO Mindstorms robots).  Come on people, copy-paste!  :)

Update: Make fixed my name, thanks!  Now I just need to perfect my time machine so I can go back and correct MacTech.

Check this out, MacTech did an article on using the LEGO MINDSTORMS NXT on a mac and talked about ruby-nxt. Even linked to my website. Unfortunately, they spelled my name wrong! :)

I’ve been pretty busy lately so haven’t had much time to work on ruby-nxt. However, tonight I had some time to finally get it packaged into a gem! The main reason it took so long is because of some kind of weird bug with requiring ruby-serialport and rubygems resulting in the following error:

NameError: (eval):1:in `private_class_method': undefined method `create' for class `Class'
        from (eval):1
        from (eval):1
        from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
        from (irb):2

For some reason, it doesn’t like rubygem’s custom require code. So I got around it by doing a Kernel::require “serialport”.

Unfortunately, there’s really no way to include ruby-serialport in the ruby gem, so you’ll still have to download and install that seperately. Once serialport is installed, all you should have to do is sudo gem install ruby-nxt. Then in your code require “rubygems” then require “nxt_comm” or require “nxt” depending on how you want to use it.

The 0.8.1 release doesn’t have anything new in terms of features, however you might want to take a look at examples/drb_server.rb ;)

We’ve made quite a lot of progress on ruby-nxt. The new version is a pretty complete implementation of the NXT direct command set. Almost everything is pretty well documented now, too. One of the more interesting things I’ve been working on is a high level api based on the “blocks” in NXT-G. So if you’re familiar with the way NXT-G works, you should be able to pick it up pretty easily with code such as:

t = Commands::TouchSensor.new(@nxt)
t.port = 1
t.action = :pressed

while t.logic == false
  puts "Hold down the button..."
  sleep(0.5)
end

Now that it’s pretty complete and usable, I think I’ll finally get around to making a Ruby on Rails plugin, which was the original reason I started all this! :)

I haven’t had much time to work on ruby-nxt because I was away on vacation (cruise to alaska). While I was away, Matt Zukowski has expanded it adding some more higher level functions and setup a rubyforge project. I will be moving development there instead of my local subversion repository, so make sure you switch to it if you want the latest version. Now that I’m back, I plan on spending a lot more time on it.

I made a lot of progress this weekend on ruby-nxt. I got most of the Direct Commands completed. Update: ruby-nxt can now be found at rubyforge.

It makes programming the NXT as simple as:

require 'nxt.rb'

NXT.exec("/dev/tty.NXT-B") do |cmd|

  puts "Battery Level: #{cmd.GetBatteryLevel[0]/1000.0} V"

  cmd.PlaySoundFile(true,"Good Job.rso")
  sleep(3)
  cmd.StopSoundPlayback

end

Once I get it a little more polished, I plan on also creating a Ruby On Rails plugin. Forget Microsoft Robotics Studio. ;)

Following up on my ruby nxt datalogger from yesterday, I’ve got two way communication working now. Doesn’t do much yet, just sends a play tone command to the nxt, sends a bluetooth message, or read a mailbox. It’s a start.

Unlike the datalogger, this requires creating a serial port for the NXT device using Dev B service. (in OSX that’s under Bluetooth Preferences -> Devices -> NXT -> Edit Serial Ports. Device Service: Dev B, Port type: RS-232, require pairing for security)

Also, if you want to send messages to a program running on the NXT, make sure you run this script first before starting your program on the NXT.

One problem I can’t figure out is I created an NXT-G program and made it send a bluetooth message on connection 0 but I get no output on the serial port… however, if I go into the NXT and tell it to connect to my computer using my datalogger I get output there. The NXT shows my computer as being connected to both connection 0 and 1, which I thought wasn’t possible. The documentation says the NXT can only be a Master or a Slave, not both. So who knows.

require "serialport"

@tty = SerialPort.new("/dev/tty.NXT-B", 57600, 8, 1, SerialPort::NONE)
@tty.flow_control = SerialPort::HARD

puts "bluetooth SPP connected"

if fork

  puts "input thread started"

  while (res = @tty.getc)
    puts "Response: %02x\t%s" % [res,res]
  end

else

  puts "output thread started"

  # play tone
  tone_cmd = [0x05,0x00,0x00,0x03,0xff,0x00,0x10,0x00,0x00]

  # write True to mailbox 0
  write_cmd = [0x06,0x00,0x00,0x09,0x00,0x02,0x01,0x00]

  # read mailbox 0 from slave?
  read_cmd = [0x05,0x00,0x00,0x13,0x0A,0x00,0x00]

  while true
    while (key = STDIN.gets.chomp) do
      if key == "w"
        puts "MessageWrite"
        write_cmd.each do |b|
          @tty.putc b
        end
      end
      if key == "r"
        puts "MessageRead"
        read_cmd.each do |b|
          @tty.putc b
        end
      end
      if key == "t"
        puts "PlayTone"
        tone_cmd.each do |b|
          @tty.putc b
        end
      end
    end
  end

end

I just finished writing a simple ruby script that listens for messages from a LEGO Mindstorms NXT robot on a bluetooth serial port and print out the messages in a comma delimited format with a datestamp, mailbox the message was sent to, and the message itself.

I’ve only tested it on OSX so far, but it should work on linux and windows so long as you have ruby and the ruby-serialport module. It’s a little rough at the moment and probably buggy. I couldn’t find info on the incoming message bytecodes in the NXT Dev Kit. Found the info in “Appendix 2 - LEGO MINDSTORMS NXT Direct commands.pdf” pages 5 and 9. There doesn’t seem to be anything in the message header to indicate what type of message it is (Text, Number, or Logic), so I had to kind of fudge it. If the info is in the docs, please let me know. I put some comments in the code describing the different bytecodes I was able to figure out.

You can always download the latest version of nxtlogger.rb using this link.

Update 2006-08-05: Made the code much cleaner. I’ve never worked with low level binary data before. :)

Instructions for connecting NXT to OSX via bluetooth.

One step closer to chunky robotic bacon!