Karen,

David's solution may help, but it's possible to have pieces of broken 
wire that are simply impossible to find. Just to make sure everyone's 
on the same page:  the "broken wire" in question is not a physical 
wire, it's a programming wire that (when not broken) connects the 
data hubs of two programming blocks. Those of you who use wires know 
that a broken wire shows up as a dotted-gray line, whereas good wires 
show up as solid, colored lines.

You may find the wire by moving blocks around, but some wires resist 
being found, because they're very short or hidden behind blocks. 
There is a solution, recommended in "The Lego Mindstorms NXT Idea 
Book." Quoting from that book:

>Thankfully there's a helpful tool to fix this. Due to some 
>incredible foresight on the part of the designers of NXT-G, not only 
>is the language extendable with features such as MyBlocks, but the 
>programming environment is as well. One of the tools that has been 
>developed and can be installed into NXT-G has the name "Remove Bad 
>Wires." ... Remove Bad Wires is an extension of the programming 
>environment that just needs to be dropped into an internal folder of 
>the applictaion. Once there, it appears in the pull-down Tools menu 
>as an item you can select. It will simply go through and delete 
>every broken wire in the program, saving you the trouble.
>
>To install:
>
>1. Create a folder or directory called "project" in the MINDSTORMS 
>NXT engine folder or directory (if there's not already one there).
>
>2. Drop the addition (called a VI) into it.
>
>3. Restart NXT-G.

The code may be found by going here:
http://forums.nxtasy.org/index.php?showtopic=444&mode=threaded
and downloading the file RemoveBadWires.llb at the bottom of the forum post.

Hope that helps!
Mike




>I've heard others recommend  downloading the latest firmware so I 
>suppose that's a good place to start.   If you are still seeing the 
> problem, then I would isolate the problem block by removing 
>sections of the program until you get the download to work.  ( don't 
>save the file).   Once the block is isolated then replace it with a 
> new one.
>
>That seems to work for my team although if there is a 
>better solution, I'd sure like to hear it.
>
>David
>
>
>On Nov 2, 2008, at 6:03 PM, Karen McSweeney Contreras wrote:
>
>>We are suddenly having trouble with our robot accepting downloads 
>>from our laptop computer.  We get an error message on the laptop 
>>computer that says "There is a data wire that does not have a data 
>>source.  Error # 5021."  But there do not appear to be any wires 
>>that are not connected!!  We tried connecting a different NXT robot 
>>to the laptop and we get the same problem; so we know it is the 
>>program, not the robot.  We deleted the program and reloaded it. 
>>Nothing has helped.
>>Any thoughts on a solution or where I can find a solution?
>>
>>
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