SimLearn

This is an ongoing series of screencasts on how to use Bram Fokke’s NXT# components to control the NXT over Bluetooth. This will be just a test to see if the computer can connect to the NXT over Bluetooth. I’m following the instructions provided on Bram’s site to create a simple C# application that connects to the NXT. Each step outlined below has a corresponding screencast, and I will keep adding to it. Note that I’m a complete novice to C# and have just ordered Learning C# by Jesse Liberty and Brian MacDonald. So, if I’m taking the long route on any of these steps, please post a comment and I’ll fix it.

1. Pairing the NXT as a slave via Bluetooth in Windows XP.
2. Installing NXT# components into Visual Studio 2005.
3. Creating a new application that connects to the NXT.

I was able to reestablish the Bluetooth connection on three different occasions. Only twice it did not connect. Hopefully the success can continue. One thing I learned is that occasionally you must just shut off the NXT brick and then try and reestablish the Bluetooth connection.

Managed to get iCommand working on MacOSX Tiger 10.4.10 (running on an Intel iMac) after a few hours. I followed the instructions in the README.txt file in iCommand-0.6 folder. The brief, but accurate instructions on how to compile the sample programs using the Eclipse IDE also came in handy. Tony Buser’s instructions on pairing the NXT over a serial port as a slave is a useful reference as well. The iCommand README has instructions for Windows, Linux and MacOSX with several alternative options for each. I’m listing the options that worked for me (mostly a copy-and-paste from the README).

1. Download iCommand (version 0.6 as of this writing) and Unzip the contents into a directory (Desktop is fine).
2. Copy icommand.jar to the Java extensions directory /Library/Java/Extensions/.
3. Download RXTX java binaries for source/Mac OS X and Unzip [rxtx-2.1-7r2.zip (Final) as of this writing].
4. Copy files RXTXComm.jar and rxtxSerial.jnilib (inside the rxtx-2.1-7r2/MACOSX_IDE/ForPackageMaker/install/Library/Java/Extensions folder) to the Java extensions directory /Library/Java/Extensions/.
5. Create the /var/lock directory with the command sudo mkdir /var/lock using he Terminal application (I didn’t find it necessary to create /var/spool/uucp directory and add yourself to the uucp group as indicated in the README).
6. Make /var/lock world writable with the command sudo chmod 777 /var/lock from the Terminal.
7. Pair your NXT and your computer using the Bluetooth setup assistant following Tony Buser’s instructions.
8. Edit the icommand.properties file ( inside icommand-0.6/dist folder), uncomment the line specifying the serial port and set it to the serial port name from step 7. You can edit the file using TextEdit and the port specification would normally be nxtcomm=/dev/tty.NXT-DevB-1 . If you have changed the name of your NXT the port would be something like /dev/tty.YOURBOTNAME-DevB-1 .
9. Copy the icommand.properties file into your home directory (/Users/YourUserName directory).
10. Download and Install Eclipse Classic for Mac OS X (Europa build 3.3.1 as of this writing).
11. Start Eclipse and create a new Java project (File > New > Java Project and give it a name – I called mine robotest). Click on the Finish button when done (see screenshot).
12. Import the icommand sample programs into your project. Expand on your project folder in the Package Explorer and select the src folder. Now choose Import… from the File menu (see screenshot). Expand the General folder and select Filesystem for the Import Source in the resulting dialog box (see screenshot) and click on the Next button. Then select the samples folder inside icommand-0.6 folder in the resulting dialog box by clicking on the Browse… button. Make sure the checkbox next to the samples folder is checked and click on the Finish button (see screenshot) .
13. Open the RadioControl.java file that is inside the default package in your Eclipse project (see screenshot).
14. Make a simple 2-wheeled robot (or hook motors to port A and B).
15. Make sure the NXT is on and Bluetooth is turned on in the NXT.
16. Compile and run the RadioControl.java program (Shift-Command-F11). The RadioControl application window will open a window (this is a blank window with no UI). The computer will connect to the NXT (bluetooth indicator on NXT will turn into a diamond). Use the arrow keys to move forward, back and turn.

If you get an gnu.io.PortInUseException error it usually means that your application terminated prematurely and the lock file didn’t get cleared. You have to manually delete it before it will work again from Terminal. Go to the /var/lock folder and delete the lock file using sudo rm lockFilename . The lockFilename is something like LK.003.009.014 .

If you have problems connecting to the NXT; delete the NXT device in Bluetooth preferences and pair it again as described in step 7. I find that the computer connects to theNXTalmost instantaneously and command response is near instantaneous as well. This is a very viable way of remotely controlling an NXT.

At our meaning on Friday, we were able to remotely control the grabber device using Bluetooth.  This is a major, major breakthrough.  Interestingly enough, we were controlling the robot using a program made in Visual Basic.   Hopefully we are able to reestablish the Bluetooth connection in the next couple days.  I am cautiously optimistic.  At least we know it is possible to remotely control the robot from the computer.

Steve Hassenplug’s NXT site has a feature comparison table of NXT programming environments and off-blick controller software.

Here is a look at an interface someone made to connect to the NXT brick using bluetooth. The link is here.

Lego has published a list of bluetooth devices that work best with the NXT brick.  Hopefully we can get our computers to connect.  If not, maybe we can use one of the “compatible” bluetooth adapters on the list. 

This camera connects directly to NXT and supports tracking of upto 8 objects.

NXTBrowser is a bluetooth file browser for the NXT. It is a Universal application and works on Intel Macs.

Nice article in MacTech magazine by Rich Warren on how to control an NXT over bluetooth using iCommand and ruby-nxt.