BlueTooth Disconnecting
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Author:  Paul Woughter [ Fri Mar 01, 2013 12:29 pm ]
Post subject:  BlueTooth Disconnecting

This is the first year my robotics class has been using NXT based robots using RobotC. We've been able connect, download, program and control our robots with Bluetooth with generally no issues. However we've been having the issue of one group controlling their NXT properly then getting disconnected when another group attempts to pair up with their robot. This diconnection occurs right at the end of the 30 second search.

As you can imaging first team gets annoyed, reconnects to their robot, propmply disconnecting the second team and everyone else in the room trying to connect.

We've tried various solutions, resetting, removing devices, reloading driver,s etc. with no luck.

What I'd like to know but can't see to find anywhere is;

Can you control two robots from two separate computers in the same enviroment? I would assume so but can't seem to find any information on it. If so do you folks have any reccomendations how we can proceed to get a couple of robots controlled by bluetooth? We have traditionally had a friendly in-class competion I realy don't want to go back to our old broken (through excessive use) down Vex robots with RC control.

We are running ver 3.54 and the latest firmware. We're using 64 bit Windows 7. Unfortuantly I can't give you the details on the BT devices as we actually have 4-5 differents one and we're having the same issue on all of them.

Thanks in advance for at help, advice, or even comiseration.

Author:  JohnWatson [ Fri Mar 01, 2013 4:41 pm ]
Post subject:  Re: BlueTooth Disconnecting

It sounds like the individual computers are picking up each other's NXT bricks and connecting to them. I would suggest naming each NXT separately (NXT-A, NXT-B, NXT-C, etc) and making sure each student is only connecting to their NXT brick. You can rename NXT bricks through the 'NXT Brick Download' window (which appears when you download firmware to the NXT).

Also make sure that the NXT's are paired to the computers correctly; we have a ROBOTC wiki guide on how to do this, which can be found here:

As you add more Bluetooth devices to the classroom that are running at the same time, you may notice some slight interference from time to time, but it's usually not enough to cause the NXT's to lose connection to the PC's. How many NXT's are you normally running at the same time in the lab?

Author:  Paul Woughter [ Mon Mar 04, 2013 8:28 am ]
Post subject:  Re: BlueTooth Disconnecting

We typically have 4-5 groups using an NXT or NXT based Tetrix robot daily.

We have given the bricks unique names but not necessarily unique passwords. We've generally had no issues connecting an individual computer to a specific brick. Based on your wiki page, the issue becomes right at the end of step 3 at the end of the search. When the menu comes up to select which brick to connect to, any other brick using Bluetooth beeps like it just connected (but its not connected to the computer doing the search) and the user loses control and the connection no longer responds.

We are going to try a compete reset today, removing all Bluetooth devices, all pairings, etc. and see what happens.

I know you can have multiple robots connected to different computers using joystick control as I've personally been to several competitions and seen it work just fine. I'm not sure what settings we've managed to stumble on that causes this.

edit for bad typing

Author:  Paul Woughter [ Thu Mar 07, 2013 9:35 am ]
Post subject:  Re: BlueTooth Disconnecting

I believe we have solved the problem. After re installing all drivers, changing passwords, changing brick names, etc. I got my hands on a couple of Bluetooth dongles from another manufacturer. The problem of disconnecting at the end of theconnection search vanished immediately.

The dongles that were causing the problem were Diamond Multimedia BT200's. Even after downloading and installing the current driver from the manufacture's site we continued to have the problem.

Author:  tfriez [ Thu Mar 07, 2013 10:14 am ]
Post subject:  Re: BlueTooth Disconnecting

Glad to hear you got everything working!

Some bluetooth chipsets can be particularly painful to work with when using the NXT. We've found that using 3rd party driver/software (as opposed to windows' native drivers) causes more connection issues - specifically software like BluSoleil. There are also some bluetooth chipsets that just simply won't communicate to the NXT. Because ROBOTC uses the LEGO provided drivers for communication and bluetooth enumeration, there isn't much we can do to improve this process.

If you can, post the model of the working bluetooth dongle so others may be able to find them as well.


Author:  Paul Woughter [ Thu Mar 07, 2013 10:32 am ]
Post subject:  Re: BlueTooth Disconnecting

The dongle that worked is the Abe dongle which we purchased originally from legoeducation. We didn't have enough for all our kits and I purchased the others out of my pocket. Its just difficult getting a $40 dongle past the folks who approve our IT materials.

Author:  JohnWatson [ Fri Mar 15, 2013 6:42 pm ]
Post subject:  Re: BlueTooth Disconnecting

I apologize for not posting this link directly as well (it is at the top of the wiki page that I linked as well), but Laurens Valk has a great listing of all the NXT-compatible bluetooth adapters that he has tested; you can check it out here. If you like his work, make sure to tell him so in his blog's comments!

Author:  Paul Woughter [ Mon Mar 18, 2013 10:08 am ]
Post subject:  Re: BlueTooth Disconnecting

We were actually using the second dongle on that list. We had no issues installing and connecting them to the NXT bricks. This issue showed up when we started working with multiple computer/robots pairs at the same time.

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