On Sat, Dec 18, 2010 at 1:41 PM, Max B <skinkworks42@gmail.com> wrote:

NXT bluetooth has extremely high latency specific to the NXT communications protocol.

Would it be possible to work around this by writing an NXT program (or firmware) that checks the bluetooth every so often for commands, acts on those commands, and feeds back sensor data to the computer? MSRS uses this approach to NXT development.

I am on an FTC team, and our robot can get joystick messages at 10Hz over bluetooth, which is much faster than ROS can send the motor commands to the NXT.

It is my impression that it is a hardware issue for the NXT radio switching between send and receive mode. I've attached some references below, though I can't find the best writeup I remember reading.

We determined that the performance of the bluetooth was inadequate for closing the loop for over bluetooth and decided not to optimize the ROS interface. You'll find that much of the current bandwidth is used for reading from the sensors at high rates. Optimizations could be made so as to batch up messages and send them together so as to not require the bluetooth radio to switch directions as often.

Tully

http://www.tau.ac.il/~stoledo/lego/btperformance.html
http://lejos.sourceforge.net/forum/viewtopic.php?p=8972&sid=47e39507ce3c3944b196466737a6794b
http://forums.nxtasy.org/index.php?showtopic=4320 Link broken, it might come back but I think not. I haven't been able to find a copy anywhere.