Oct 18, 2006

NXT and Bluetooth Problems (Revisited)

As most everyone now knows, NXT Bluetooth connections can be fickle at best. (Much has been written about this on this blog).

Bram Fokke has his own cure for an ailing Bluetooth connection: scrap the propietary drivers and just use the ones provided by Microsoft on Windows XP. (You have to have Service Pack 2 to do this).

After a long-used Bluetooth connection of mine suddenly went south, I tried Bram's advice and it worked. His article is appropriately entitled, "Bluetooth Brawl". Read ithere.


Jim Kelly said...

Yeah, I enjoyed Bram's article, too... I didn't realize BT was this shaky.


Sivan Toledo said...

I don't think that shaky is the right term here. Because Microsoft was slow to come up with working BT drivers and even with a standard that would allow an application to work with any driver, manufacturers created their own drivers, which had proprietary programming interfaces. This made writing BT application software hard. When the NXT software was implemented, they apparently decided to support only two drivers, the one that Microsoft eventually released in SP2, and one by WIDCOMM. So if you use some other BT driver (because it came with the dongle), there is no change that the NXT software will be able to use it.

Anonymous said...

When i plugged in my bluetooth dongle i had no problems using the microsoft drivers that were installed automatically. I could use the LEGO program without any problems.

The thing that i COULDN'T do is use microsoft robotics studio because apparently (i forgot where i read it) it requires the PC to be a slave and the microsoft bluetooth stack does not allow this. If you are interested in getting microsoft robotics studio to work then try this article i wrote. http://nxtemplar.blogspot.com/2006/10/bluetooth-nxt-robotics-studio.html
Unfortunately the LEGO program will not work anymore so you will have to use the USB cable for that.

If you use anything that does not require the PC to be a slave then the Microsoft bluetooth stack is probably the best option.

Anonymous said...

Oooops sorry i used the wrong tags for the link:


Anonymous said...

:( Im having a bad day

Bluetooth, NXT, Robotics Studio

Anonymous said...

:S I tried to uninstall the software that was included with my BT dongle and install the dongle with Windows

It didnt work :S

Anonymous said...

We, too, suffered from very frustrating Bluetooth troubles. I use a cheap Bluetooth USB dongle, using Windows XP drivers (on a desktop) and Vista drivers (on a Laptop). On both computers, when 'scanning' from the Mindstorms software, the NXT would come up 'available'. Then, when trying to connect, a window popped up requesting the passcode (at the PC), then NXT would beep and request a passcode as well. After pressing the orange button, an error would occur in the Mindstorms software ("Error: a connection could not be made" or something vague like that). Because the error only came up at such a late stage in the connection process, I suspected that the Bluetooth hardware would be OK, but somehow a higher software layer caused the problem. After a lot of experimenting, I found a procedure that creates a Bluetooth connection, which works both on the Desktop (XP-SP2) and the Laptop (Vista). Some steps may not be needed, or alternative sequences might work, but this does it for me:

1. Switch on the PC

2. Slide in the Bluetooth dongle (my PC doesn't boot with the dongle installed)

3. On the PC, open the Bluetooth Devices window

4. If any NXT device is listed in the Devices list, Remove it (otherwise, a 'Line Busy' error will pop up later). Make sure 'Turn discovery on' is selected. Close the Bluetooth Devices window.

5. Switch on the NXT, and select 'Search' from the bluetooth menu, then 'Connect' to the found computer. Accept the passcode.

6. On the PC, a window comes up mentioning that a Bluetooth device is requesting to connect, asking if you want to allow connection. Click on the message to allow connection. A new window pops up, asking for the passcode. Type in the passcode and click Next. Again, the NXT beeps to verify the passcode; press the orange button on NXT to accept.

7. Open the Bluetooth Devices window. Select the NXT device and press 'Properties'. In the new window that opens, click the 'Services' tab. Now, Windows starts searching for services that NXT supports. Select all available services (in my case, two serial ports) and press OK. Windows now installs some new drivers. After that, close the Bluetooth Devices window.

8. Now, start the Mindstorms software on the PC, and open the NXT window. Scan for NXT devices, and after finding NXT, click "Connect" (if not already connected during scanning).

9. YES! It works! (for me anyway).

My guess is that with the above procedure, Windows not only recognizes NXT, but also knows with what type of connection services to approach NXT. Apparently, this allows the Mindstorms software to actually create a connection. Unfortunately, the sequence is a bit complicated, which is a problem for my son, the biggest Mindstorms user. Any help in shortening the sequence is appreciated.

I hope this is of any help to other frustrated NXT owners having Bluetooth problems!

Anonymous said...


i am having problems with detecting my NXT from BRICXCC. Although my NXT and PC seem to be connected, when i'm running BricX Command Center, and select Bluetooth, i get the following message "unable to connect to the programmable brick". I have Windows XP PRO with SP2 installed but its drivers seem not to detect my NXT at all. I have installed WIDCOMM and still no problem solved. If i go in my Bluetooth places, i see that NXT is connected through serial port com 8. Can anyone tell me what to do, or where do i go wrong? This thing is driving me nuts :((

daveandhank said...

I am also having trouble connecting via bluetooth. I am primarily inserested in driving the NXT via MATLAB, either via the package provided through the lego site (http://www.mathworks.com/programs/lego/) or the RWTH site (http://www.lfb.rwth-aachen.de/en/education/ws07/mindstorms.html . But it doesn't work. I liked the recipe for getting the "cheap bluetooth dongle" to work - but which dongle!? It's impossible to follow without that information. I am trying to use the one that shipped with my NXT. Not only does MATLAB not shake hands correctly, it actually crashes unrecoverable when I try it - and cryptically says 'port COM3 not available. Available ports are COM1, COM3, COM5'. My outgoing port is COM3 and incoming is COM4 - anybody seen this?


Anonymous said...

Everything almost worked for me using the Bluetooth drivers that come with Windows XP SP2. Almost = I hit "Access Denied" when trying to configure the laptop to open a serial port to the NXT device. I had to manually edit registry permissions and explicitly allow myself access to HKLM\SYSTEM\CurrentControlSet\Services\BTHPORT. Details at http://support.microsoft.com/kb/892891.

GrizzledGeezer said...

I have the same problem with W7 and the Windows drivers. If there is a solution, I'd like to know what it is.

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