Rolf Kalbermatter

Do you call the DAQmx Reserve Network Device.vi in your LabVIEW code?

No VLC could not be aware of anything besides the HWND boundaries at all, since everything inside a VI front panel is LabVIEW specific and not visible to anything that only knows about Windows details. It would be definitely a case of a VI panel being used for nothing else but a HWND container and there is no sensible way of sharing that with any LabVIEW controls or whatsoever in the same Window. It is even worse than that, as VLC can not know if you overlay that panel by something else in LabVIEW. On the other hand VLC does not have to worry about blitting only within the Windows bounderies as long as it uses GDI or friends for it. Windows will make sure that any blitting will only occur in the window boundary no matter what. That changes of course if VLC would do direct blitting into graphics frame buffers, but as far as I know this is strongly discouraged by Windows and actually made very hard since it requires hardware specific code which is able to deal with various graphics card drivers.

Rendering is obviously an issue, but ActiveX is not the solution here, as it is at best a "briccolage" as the French say. The most simple way would involve some copying of the data into a LabVIEW Indicator like the Picture Control. Not ideal in terms of performance but at least doable in any LabVIEW platform without issues about overlapping and such. I would love to be able to create my own control like the IMAQ control, but alas that is not an option for us mere mortals as it requires to much NI internal only knowledge about LabVIEW. The second best would be to use a VI panel as a sub panel and reserve the entire VI as render surface. Extract the platform graphics port (HWND on Windows) and pass it to VLC to let it render its output directly into it. there will be issues with overlap of other elements with that Window but ActiveX has that too, and the only way to get that right is to hook into the internal LabVIEW object messaging which is not an option without serious access to at least some parts of the LabVIEW interna.

Writing ActiveX Controls if there are other solutions is only for real masochists . Go the DLL path, that gives you a lot more control in the debugging process, avoids an entire level of obscure Windows 3.1 imposed limitations, and a few more levels of intermediate bullshit, and last but not least if done with a little planning in mind, you can port it to every single platform that LabVIEW and VLC support without to much effort.

The meaning of this bitset is private to LabVIEW and undocumented. As such it is also highly susceptible to changes and completely incompatible reeinterpretations between LabVIEW versions. Some of the more trivial modifications like front panel or diagram changes can be quite easily deduced but there are many obscure modifications in LabVIEW that get recorded in this bitset that nobody without access to the LabVIEW source code could ever guess. Try to look in the VI Properties->Current Changes dialog and see what it mentions there. You might be able to deduce some of these bitflags from there, but quite a few bitflags are lumped together in more common modification reasons.

Well the approach chosen in that paper is rather cumbersome. It means you have to create a CIN or DLL for every operation you want to perform, with an external filename whose name is compiled into this external code. Yes it gives the flexibility to change the actual Ch code by changing the external file contents, but it is highly coupled in a logical way and highly decoupled in a process way, in fact the total opposite you would want with a scripting solution. Using an interpreted C environment in a way that requires to write a VI that interfaces to compiled C code for every individual problem is quite an involved way. That may work if you have a specific problem to solve, whose algorithme needs fine tuning in the field, but it doesn't feel like a general purpose approach to integrating scripting into LabVIEW, or any programming environment actually.

Well a circuit always needs to have some reference somehow. For isolated modules like this it means that either your sensor or the analog input needs a reference to some form of GND. This can be the GND of the power supply to power your cRIO. Without ground reference, the entire circuit is floating and static charges eventually can get it to a level that exceeds the common mode range of the input amplifier, resulting in saturation and according misbehaviour of the amplifier. The advantages of isolated amplifiers is that they can measure signals that are referenced to a different potential than the actual measurement system uses (of course the difference of reference needs to be lower than the isolation voltage or you get a breakdown). In case the measurement signal is not referenced in any way you need to provide a reference yourself. This may seem like using an expensive isolation amplifier and making that isolation undone by the common reference, but the isolation amplifier still serves as protection for your measurement device (and the operator sitting at the computer connected to it) from high voltage surges such as what is caused by lightning, provided the ground reference is strong enough to dissipate those surges.

I guess it could be integrated in LabVIEW in a similar way than Lua through LuaVIEW. But as current maintainer of LuaVIEW I don't see much merit in getting my time fragmented even more with yet another scripting interface for LabVIEW. The wiki page certainly looks problematic and the license doesn't make it the first choice for a scripting interface either.

Why in all of the world do you want to use Windows messages to communicate between two VIs? This has only disadvantages, from being a platform specific solution, to making everything rather complicated, to being of low performance!

Basically your Windows desktop is simply an application that is started up by Windows after the user logged in (or it logs in automatically). You can change the registry entry for this to any program you like, including a LabVIEW app. Needs some careful planning ahead, because once you do that, you mostly only can do things in Windows that your application provides an interface for. So if you don't plan some way to startup for instance the file manager, you might have locked out yourself for that account pretty effectively. One exception is Ctrl-Alt-Del which still works, but with some Windows API magic, this is quite easily remedied too. A computer that is tied down like this is pretty hard to get into in other ways than your Shell replacement app, but again watch out, this applies for you too, not just the operator noob.

It's the low level device name notion for modern Windows systems before any disk drives are mapped on top of it, so I doubt that it is something LabVIEW does on its own explicitedly. Somehow somewhere Windows seems to have mount points or whatever that point to a hard-drive partition that doesn't currently or anymore exist on your system, and maybe LabVIEW tries to enumerate those disk drives or mount points at some point and triggers this error message. Try to do a registry search for the HD volume name, maybe it exists in there and may even point you more into a direction what could have caused this. Have you at some point used removable harddisks with NTFS formatting?

Thanks for the clarification. In that case it seems like a good solution unless the directory rights silently get modified too. I should test that but am currently tied up with quite a bit of other things.

Incidentally exactly the error codes I mentioned in my reply that you can't just always honor or ignore, as it depends on the situation where they occur, what you should do about. Timeout means usually that there simply hasn't been data and you should retry after a reasonable amount of time whatever you tried to do that gave you a timeout. This can be a Read, or a Connect or a Write operation. You should build some retry limit into it as it makes usually little sense to try endlessly. If after several minutes there is still no peer to connect, there might be a bigger problem like a disconnected network cable. Peer disconnected is another error that can happen because of network failure and that you can handle totally transparent by closing your network connection and attempting to reconnect again. Last but not least you should of course consider the timeouts you use for the various functions. When you do a connect with a 120 second timeout the connect will wait that long likely preventing your application to quit when you hit the quit button until it gets the requested operation (connection for a connect or data for a read), encounters and error or the the timeout occurred. This is probably the reason that you believe that you can only Ctrl-Alt-Del your application as the network functions simply sit in a timeout waiting for something. One thing that usually works to terminate most network functions in LabVIEW is to actually Close the network refnum that they operate on. This is not really good programming for normal network refnums and might fail sometimes but the perfect way to terminate the listener loop, when you would have a TCP Listener somewhere in your program. So wherever you handle your Application close request, get a handle on those network refnums and close them. That "should" make any network operation that is waiting on that refnum to return with an error. Better would be to make your network communication use much smaller timeouts and handle the close request themselves by polling a global close state controlled by your application close handler or if you start to do real software design some day , use some producer consumer framework throughout your application to handle those 10 loops correctly and in a fully controlled manner.

What messages? How does your code look? Is auto error handling the only error handling you do in your code? Network communication is not something that you can simply expect to work always. Your code needs to be able to handle all kinds of possible errors such as timeouts, the peer disconnecting etc. in order to get a reliable operation. Depending on the error and your application you can sometimes ignore it (read timeouts for instance) or should close the connection and attempt to reconnect (client) or wait for another connection attempt (server).

Haven't checked out how they did the silver controls, but being graphics and all I have a suspicion that it is either a Video Driver or maybe even specifically a GPU issue. Can you see if the different revision motherboards use some kind of different chipset, or at least revision thereof. What about the video driver?

Please let us know what NI has to say about this. I'm going to be in this same spot soon and it would be nice to know why I need to distribute deployable licenses for a runtime app.

Ok on my own machine I usually run with an account that is part of the admin group and the other computer is a standalone system with only one local user with local admin rights. But reading through it, it all makes sense. Since Vista, MS has tightened security according to the principle that a user should only have access to resources that do not influence other users on a system. This includes the entire registry except the user specific hive, the filesystem including all setting directories that are used by all users. So ProgramData logically belongs to that. I just added a small piece of code that checks in the configuration dialog the write rights for the configuration file, and if that is not there of the directory and only enables the Save button if this is true. A dialog informs the user that the application needs to be started as admin in order to be able to make changes to the relevant configuration items. Since Vista you have to differentiate between elevated rights and a user account that has admin rights. The difference is that in order to be elevated one has to start the process explicitedly as admin with an extra password login dialog, even if the current user is already part of the admin group. Your solution has one possible drawback. Only changing the rights of the config file alone is likely not enough as the directory needs to have its rights also changed. And that allows access to the directory to add more files to anybody, although it should be not possible to change existing files that don't have write rights for normal users.

I want to know that too. I'm using Windows 7 Professional here in 32 Bit and 64 Bit on another machine and ProgramData/<Company Name> seemed to work quite well so far. Or where they trying to access it with hardwired names, instead of requesting the location from the OS? Or is it restricted for Guest accounts or similar?

But you typically are not going to multicast 60MB files to many stations.

To me it seems like an academic research project, and as such literally an "academic exercise". I'm sure such work is needed but I wouldn't even bother to think about using UDP to transfer larger entities that need to stay consistent. TCP is tried and proven for such things, so why it needs to be UDP is beyond me. It's not like UDP would be easier to route in restricted networks or such, so I simply don't see the benefit of going through the hassle of reimplementing some of the TCP handling on top of UDP.

Without that ini token the executable may still get started by the Windows shell, but one of the first things LabVIEW does on starting up is to try to connect a different (same version) LabVIEW instance (through DDE communication) and if it finds it it will simply pass any command line commands to that instance instead and quit gracefully.

To expand on Antoine's post besides the hidden or non-hidden location you should consider if settings are user or machine specific. Things like hardware configuration you probably don't want to maintain on a per user base, but other things like applications settings (data formats, paths, etc) your most likely will want to keep separate for each user.

You haven't shown much so far that would have made me believe that you have much of a technical understanding of those protocols. And wanting to do something is a nice thing, but if it is a useful exercise an entirely different one. Considering some notices in the paper about how the difference in calling socket functions can have a significant influence in lost buffers, I think LabVIEW might be not the ideal environment to tackle this research. You have no control whatsoever, in how LabVIEW handles the socket calls. In addition it adds it's own network data buffering that you can only influence in limited ways from the LabVIEW nodes. And no I'm not talking about controlling socket attributes by calling socket API functions directly, but how LabVIEW calls recvfrom() and friends itself.

To me it looks like IEC61850 is not about transfering large files consistently over the network. To do that over UDP is really not a smart idea as you have to implement on top of UDP something similar what TCP does already for you. An interesting side node to this: A while back I was looking at the network protocol used by Second Life and other compatible virtual world environments. They used to have the entire communication over UDP with their own sequence handling, acknowledgement and retransmission requests. The reason to go for UDP was supposedly the low overhead that was required to make movement and interaction in a 3D virtual world possible at all. However a few years ago they did introduce a new mechanisme for non-realtime critical messages and are porting slowly more and more of the messages over to this new mechanisme. It is basically a HTTP based protocol where the packet load is usually a data structure in their own LLSD format, which is in many ways similar to JSON. And yes I have implemented some basic messages in LabVIEW that got me as far as logging into a virtual world server.

UDP is not a reliable protocol. Unless you intend to do A LOT of extra error handling, packet sequence management, lost packet retransmission and what else, you can forget to use it for transfering a file that needs to stay consistent.