NXT communication mailbox fails

[DaVince]

Hi everyone,

I'm working with the Mindstorms 2.0 kit and using Labview 2009 SP1. I'm trying to get a message from my computer to the next using the mailbox VI. I've connected the NXT using USB. Now I'm trying the color sensor demo downloaded from here:

http://decibel.ni.com/content/docs/DOC-11109

Now I've uploaded NXT_Client using the NXT [USB] instance. It says its 'running'. Now I load the PC_Host, switch back to Main Application Instance, and run. Then PC_Host gives me the message below.

Now I'm not sure why it says this, since the NXT_client is running.

It does however seems to work somewhat!? It gives me the right color, it just displays this error in every iteration of the loop.

I tried starting the NXT Shell, however, that just displays <0> when I run the PC_Host, and if I run the NXT_Client after the NXT Shell it just replaces it...

I'm not sure how this should work, but I'm not getting it to work. Anyone has any ideas what I'm doing wrong?

Regards,

Vincent

[DaVince]

I have futher looked into this problem.

To me, it seems there is a bug in the labview VI's. During the program it will run into 'BlueTooth_Write_String.vi'. (Even though I'm communicating through USB... however, this doesn't seem to be an error). Which in turn invokes SendCmdToDebug.vi.

Now, send SendCmdToDebug has 'Request Reply' boolean, which is True by default. As you can see in the diagram True means also then checks for whether or not the NXTShell is running, and give an error if it isn't! Now it is unwired in  BT_Write_String, meaning it always checks whether or not NXTShell is running. But its not! my own program is trying to receive the command.

Did anyone else experience this problem? Is it not a bug? Please let me know.

Regards,

Vincent

[Dominic.Walker]

I'm getting the exact same problem as DaVince.  It seems to me that the host VI want's the NXT to be running the NXT Shell for it to communicate. The NXT only seems capeable of running one program, so it can either run the NXT shell or the Client VI. Not running the NXT Shell causes the host to error, not running the Client VI causes no data to be sent. 

I'm going to try this on LV 2010 and see if that sorts the problem.  Then if that doesn't work I'm going to see if I can get the host VI to use the LabVIEW Bluetooth communications module in order to do the host's side of communication as idealy I want this working over Bluetooth. 

To me, this seems like a massive bug, I'm hoping I've just set something up wrong.  If anyone has found a solution to this it would be great to know.  If I have any luck I'll post here. 

[Dominic.Walker]

The same problem occurs in 2010.  I've been through the subVIs and stopped "Request Reply" and made sure Debug was off. As such, it seems to transmit data.  I think I'll just avoid using the NXT communications library and make some VIs which do similar things in a less complex way.

[Donski]

Hi everyone,

I also have this problem, I'm using LV2010 SP1 on a laptop with MSW7 32-bit. I've got Lego NXT 2.0 FW 1.31.

Does anybody got a solution to this problem?

Thanks