As Linus noted, a LEGO NXT forum such as mindboards would be more appropriate for this kind of question.

You can also try doing a web search. For example, searching for “scara robot line drawing” brings up this page:
http://www.societyofrobots.com/robot_arm_tutorial.shtml

Good luck,
Gautam

for such detailed questions about your project you should check out the Mindboards community at http://sourceforge.net/apps/phpbb/mindboards/ , which is probably a better place to discuss your problem.

Regards, Linus

I am using RWTH Toolbox to control motors of NXT and already built scara type robot arm, so far so good. I can draw lines with giving one by with writing necessary codes but I want to draw a lines or graphs from figures. Do you know a way or have any suggestions to process drawing line with a scara? How can I draw lines from the figure information which plotted as x y coordinates? I am wishing to get edge list information as x y coordinates and would like to make robot to combine them

I recommend using the RWTH Aachen Mindstorms NXT Toolbox to control the LEGO NXT from MATLAB. You can download it from http://www.mindstorms.rwth-aachen.de/

In one of the earlier comments for this post, I discussed how to use Simulink with the RWTH Aachen Toolbox:
http://blogs.mathworks.com/loren/2008/06/30/lego-mindstorms-nxt-in-teaching/#comment-30379

Gautam

Silvia

Thank you for your comments. It seems you’ve got a little version mix-up.

The toolbox 2.03 (and 2.04) uses MotorControl.rxe. The version displayed on your NXT screen should be MotorControl 1.1 (or 1.2). With this toolbox, you need to have the LEGO MINDSTORMS NXT Firmware version 1.05 installed.
So far so good. The motor class in this version is called NXTmotor (note the lowercase m). Motor precision and performance is alright, but not great.

The warning you describe (no reply time out in .WaitFor) has only been introduced in toolbox version 4.00. This version offers far better motor control. For this version, MotorControl20.rxe is required. It’s called this way intentionally by COM_OpenNXTEx to distinguish from previous versions (so renaming files doesn’t help). In order to compile MotorControl20.nxc, you need nbc.exe from the very latest version from BricxCC, included in the file test_release.zip, found here: http://bricxcc.sourceforge.net/
You can also find the MotorControl20.rxe binary here: http://www.mindstorms.rwth-aachen.de/trac/browser/trunk/tools/MotorControl/MotorControl20.rxe

Please note that MotorControl 2.* needs the newest LEGO MINDSTORMS NXT Firmware. Either 1.26 (comes with NXT-G Education 2.0), 1.27 or 1.28 by John Hansen (included in the mentioned test_release.zip from BricxCC) or 1.28 (comes with the new NXT 2.0 retail building kit).

So please don’t mix up different versions of the toolbox with different versions of MotorControl. Always take the MotorControl version which comes with the according toolbox zipfile. You can find out the toolbox you’re using (set in the MATLAB path) by typing:

info = ver('RWTHMindstormsNXT')

With toolbox 4.00, the motor class is called NXTMotor (uppercase M) by the way.

So I hope I’ve clarfied eveything. The high pitched beeping noise you describe is intended. It’s the NXT’s synchronization. It should be mentioned somewhere inside the chapter “Troubleshooting” of the toolbox documentation I believe. I’ve also added a description of this “feature” in the new documentation for future version 4.01. It keeps the motors in sync, useful for straight driving. It can be disabled using .Stop or .StopMotor.

The next toolbox release 4.01 is scheduled for next week. With this release we’ll also officially support Mac OS. The motor control in 4.00 (beta) works ok, we fixed some minor issues for 4.01, but overall 4.00 is pretty stable and should be well usable.

Don’t hesitate to ask further questions. Keep watching http://www.mindstorms.rwth-aachen.de for future versions, and feel free to open a ticket with feature requests or bug reports if needed.

Regards, Linus

I am using version 2.03 of the RWTH – Mindstorms NXT Toolbox on a MacBook and Matlab 7.6. I am able to communicate via bluetooth. I can play a note and read from the sensors. I am having trouble with the motors. I have uploaded the MotorControl.rxe file to the NXT.

If I run

handle = COM_OpenNXT('bluetooth.ini');

the MotorControl.rxe program on the NXT is executed.

If I then run

COM_SetDefaultNXT(handle);
m = NXTMotor('A', 'Power', 50, 'TachoLimit', 1000);
m.SendToNXT(handle);
timedOut = WaitFor(m, 5);

I get the following warning:

Warning: There has been no reply (time out) for at least 5 seconds from the
embedded NXC program MotorControl, which should be running on the NXT
brick. Please make sure the program is running and does not get terminated
accidentally. Exiting WaitFor() and continuing...
> In NXTMotor.WaitFor at 168

Coincidentally, the file COM_NXTOpenNXTEx.m was using MotorControl20.rxe instead of MotorControl.rxe. I changed this in the m-file back to MotorControl.rxe. No luck. Next, I left the MotorControl20.rxe in the m-file and changed the name of the file on the NXT. That didn’t work either. I tried this because I wasn’t sure which m-files actually use the filename on the NXT.

I have used the DirectMotorCommand to get the motors to turn. The motors don’t rotate to the programmed value. Also, the NXT makes high-pitched noises afterwards until I turn the NXT off.

I’d like to use the NXTMotor functions rather than the DirectMotorCommand function.

Any advice for me?

Thanks,
Michele

I’d like to respond to some issues brought up in the comments here:

Bluetooth
Not all Bluetooth adapters you can buy work equally well with the NXT or with MATLAB. We tested some, and here’s the (incomplete) list as a guide:
http://www.mindstorms.rwth-aachen.de/trac/wiki/BluetoothAdapter

Motor precision
Since version 2.03 of the RWTH – Mindstorms NXT Toolbox, a way for better precision is provided. While the official NXT firmware (and previous toolbox versions) don’t provide a way to rotate a motor to a precise angle with a single command (like e.g. 90 degrees and then stop), we added this feature by a program running on the NXT simultaneously. So give version 2.03 a try and use the NXTmotor class.

Even better motor control is added with the latest version 4.00 (beta), only 10 days old :-). While it might be unstable, first results show a really great way to control motors accurately (the class is now called NXTMotor). Try out the latest version and see if it works for you:
http://www.mindstorms.rwth-aachen.de/trac/wiki/Download

Gyro Sensor
Make sure to use either version 2.04 (of the RWTH – Mindstorms NXT toolbox) or the beta 4.00, as version 2.03 has limited support for the Gyro sensor (no good calibration, only 1 sensor allowed) which is fixed in later versions.

I assume you are referring to Bluetooth interface.

You can get both the gyroscope and accelerometer data using the RWTH Aachen Mindstorms NXT Toolbox (see the GetAccelerator and GetGyro functions).

Getting the time information is tricky. With the Bluetooth interface, it is difficult to get the time at which the gyro or acceleration value was sensed. The simplest solution is probably something like the following:

  % This example uses the RWTH Aachen Mindstorms NXT Toolbox
  tic; % start of measurement
  OpenGyro(SENSOR_1);
  for i=1:100
    sensorValue(i) = GetGyro(SENSOR_1);
    timeStamp(i) = toc;
    pause(0.1);
  end
  CloseSensor(SENSOR_1);

Gautam