Rolf Kalbermatter

Thanks I will probably do some tests with this, eventhough I do not know much about XControls yet. But it's a good way to get acquinted with them. I know . In any case it has given me already a nice VI library that can read and write PNG files both from disk as directly into a memory stream. Something the built in LabVIEW solution can't do. And it even supports alpha channels although the picture control doesn't support this yet. Rolf Kalbermatter

Selling and especially supporting XP embedded on hardware for development is not easy. In fact I think it is almost impossible or you would need a well paid support program from the hardware supplier. XP embedded is not a plug in the CD-ROM, launch setup.exe and voila thing. It is in fact very far from that. If you look for such an experience you are much better of with a standard XP installation. Using XP embedded means knowing and understanding in detail how you configure a build (yes you configure the components you want to have deployed to your hardware). So it is not like purchasing hardware with a preinstalled XP embedded. XP embedded will be always installed by you, the final assembler of the system) according to the configuration you made in the XP embedded Tools. And what components you will want to install will partly depend on the hardware (where NI would probably get in with a detailed list of what modules are required) but also on your intended use of the system. So NI can not really make that installation for you as they would have to decide between installing anything, basically creating a somewhat leaner XP install, or install whatever they find necessary which would likely leave you with some lack of support for some functions. Also in XP embedded your final application is usually also part of the image that you deploy to the system. Rolf Kalbermatter

It could worsen the problem on some machines where the temp location has been configured by system admins to be deeply nested. In fact the default temp location in Windows at least under XP is something like "C:\Documents and Settings\<long or not so long user name>\Local Settings\Temp" already, which doesn't look very much like a short path to me. Rolf Kalbermatter

I've been playing around with the possibility to create VI snippets even in older versions than 2009 and during that work I was suddenly wondering about the security for this. I'm pretty sure NI has thought about this, (it's probably another reason why a VI snippet only includes the top level diagram and no subVIs) and has implemented the dropping of a VI snippet in such a way that there can not be any automatic execution of code. However trying to implement that with the available LabVIEW API methods in LabVIEW < 2009 might be more tricky. I have not yet tackled the problem of turning a diagram selection into a new VI, to create a VI snippet from and also not the problem of dropping the VI contained in a snippet into a diagram, but the latter could supposedly reuse a lot of the techniques used in the inlining tool posted elsewhere here. But in order to do any of these one has first to instantiate the VI code from a snippet in memory and that is where I started to wonder if there is any kind of VI type, XNode, XControl, X anything, that does do code execution as soon as it is opened in the LabVIEW editor. I know that some of them will execute code when they are dropped to a diagram but do any of you know of cases where even opening such VIs (through VI server, not interactively) would execute something automatically? The reason I ask this, is that if the chance for something like this exists, I will abandon this idea. Rolf Kalbermatter

Probably you were not missing anything. The applications where I used that never required to be build into an executable so I never came across that limit and therefore never tried to tackle that problem. Although I did intend to leave the VITs and their subVis external to the exe for the case we ever would attempt to do the build. But not sure if that would make a difference. Rolf Kalbermatter

It could be also a hardware error on the build in port. Doesn't happen to often but it does occur. Maybe your port got soft damage from some EMC or lightning. Rolf Kalbermatter

You happen to have a slow internet connection or maybe a slow DNS server? Rolf Kalbermatter

Well LabVIEW can do that sort of but it requires the DLL developer to dig into LabVIEW memory management functions and use them strictly! Of course this is to much asked for most of them. What I would say is that such an interface is sort of ok to be used from C code only but absolutely unsuitable to be called from anything else, be it Visual Basic, Delphi, and yes even TestStand. TestStand is not a C compiler so it should not be expected to behave like one . Rolf Kalbermatter

It's all there and you have my blessings to put it in the wiki Rolf Kalbermatter

Aaaaa! LabVIEW 7.1.1 can get very slow too to start up. Especially on machines that had all sorts of other NI software loaded such as the newest DAQ drivers, newer LabVIEW versions, etc. But go back to 6.1, (just to try out ) and that is a quick start on nowadays Dual core machines! Rolf Kalbermatter

Interesting, never had problems before with AlZip. And it is able to open its own archive! Well lets see: Here are the files compressed with the OpenG ZIP tools . Desica_Megasonic.zip Rolf Kalbermatter

What I do in this case, is wait in the caller until the subVI has opened its FP. The reason to this is that the VI is kept alive by either a VI refnum to it or its FP being open. So after the FP is open, closing the VI refnum used to spawn it is safe. You can do that with .vit too although I usually have those dynamic VIs rather in a "all VIs" top level VI that I have open when developing (and add to the build as explicitedly added VI). To put a VI Template on a diagram instead of its instantiated VI you need to drag the icon from an open VI Template (file->open) or or dragging it from the explorer into the diagram, rather than using the "Menu Palette->File Browser" method. You can also change the setting of the according VI in the build settings in your project but I admit that this is something that can easily be forgotten and the FP frontpanel property is a nice trick to make sure things work always as expected. Instantiation from a VIT is a lot more costly in terms of time needed to open it and most likely also same or worse in memory footprint than a reentrant VI. But the option to have a front panel for reentrant VIs was not there before LabVIEw 8.2 I think. Rolf Kalbermatter

This request is a little very much open ended. Should this be about a DLL that can be interface only by LabVIEW or should it also be possible to call it by other applications (VB, C, Delphi, etc)? If it is just about a LabVIEW compatible DLL, is it legitimate to have LabVIEW specific parameters (advantage: direct parameter passing, disadvantage: call to specific LabVIEW manager functions that the C programmer needs to learn about)? The Calling external Code in LabVIEW section in the online help has a very detailed chapter about how to do it from LabVIEW and with some good will can be used for the opposite too. If LabVIEW specific parameters are desirable then he would also have to read the LabVIEW External Code Reference section that describes the functions one can call from an external code to deal with LabVIEW data types. If the DLL should be generic instead, the same advices apply although to a lesser strict degree as what one would need to follow to allow calling that DLL from Visual Basic as FUNCTION. This means basically: - no C++ functions, they get decorated to an unrecognizable name - no C++ interfaces, LabVIEW can not access them in any way - You can pass C++ object pointers to and from functions but LabVIEW can only treat them as opaque pointer sized integers, there is no way it could access methods or variable members of such an object except using explicit standard C exports of the DLL that accept the object pointer as parameter. This is however dangerous since on the LabVIEW side these objects are simply pointer sized integers and it is rather easy to pass a pointer to object type x to a function expecting object type y, unless the LabVIEW programmer treats those pointers as a private refnum (which will not work for LabVIEW 64 byte since the refnums there seem still to be 32 bits, while a pointer there is 64bits) - no structures with embedded string or array pointers as parameters - all string and array pointers need to be passed as separate parameters and preferably with an extra length parameter telling the function how long the allocated buffer is (preferably in # of elements but bytes can work too with some extra effort by the LabVIEW developer). - in addition to above two parameters types only use scalars of standard ANSI C integer and floating point types as parameters - strings should be passed MBCS encoded and not as widechar or unicode8, simple ANSI is of course best whenever possible - they can be either zero terminated C string pointers or Pascal string pointers - no fancy calling conventions, it's either cdecl or stdcall for Windows and just cdecl for other platforms, if multi platform is needed do only use cdecl as it is the only calling convention supported on all LabVIEW platforms. - buffers to return data should be allocated by the caller, returning buffers allocated by the DLL is although possible not recommended if the contents needs to be accessed from LabVIEW somewhere and it will require an explicit export to deallocate that buffer later, since LabVIEW can not automatically deallocate memory not allocated by itself - alignment in LabVIEW clusters is always packed (1 byte), other alignments for C structures need to be explicitly declared to the LabVIEW developer so he can do it on the LabVIEW side by embedding extra filler bytes in the cluster but it is a better idea to actually declare these filler bytes explicitly in the C structure declaration, to avoid misunderstandings between the C programmer and the LabVIEW programmer. - no function return values other than scalars and string pointers - document if the function is threadsafe I guess that is it in a nutshell. Not sure what else you would want to tell a C programmer to make your life not to complicated to integrate his DLL into LabVIEW. Rolf Kalbermatter

I don't see any order of magnitude faster or anything. The "real" typecast method is simply a flat line independent of the size of the array. And that is not surprising since the work to be done is always the same. Also smart move to use the shift operator for the size adjustment. That way you avoid any possible rounding problems if the incoming array is of uneven length. Otherwise using the divider operator you could get x.5 which could get rounded up to the next number (not sure about the exact semantics of C in this case if both the divider and and dividend are integer, though there is a good chance that the 2 in (**arg2)->dimSize /= 2; might get expanded to a floating point number first anyhow. But why even bother about that if you can use the shift operator instead which will always do the safe thing. I guess someone at NI will soon go and add a special case code to the Flatten and Unflatten function that will do the smart thing when input and output are simply both flat arrays and the desired endianess matches the endianess of the current processor. Rolf Kalbermatter

I'm sure you guys know that already but there is a way under Windows to avoid that problem. It requires to use the Widechar Windows File API and format the path in something like "\\?\a:\path to very long filename". Not all APIs do support that and it would often fail for shell APIs but it is at least a way to circumvent that problem. Not sure about the usability of this on FAT volumes though. Rolf Kalbermatter

How did you download and/or open it? I just tried myself to download the file in Firefox 3.5 and open it with Alzip 7 and had not trouble to extract the files. Rolf Kalbermater

Transpose Array is under such circumstances usually almost a NOP. Thanks to LabVIEW having something like sub-arrays. Rolf Kalbermatter

Converted to DSC 7.1. I would expect this to be enough for DSC 8.6. Desica_Megasonic.zip Rolf Kalbermatter

It might be possible but I have some doubts. There are several reasons why it might not be possible to make a normal .Net assembly remotable. 1) Security! It is always an inherent risk to allow that with arbitrary components. If you create a component specifically to allow that you hopefully take measures to make it really secure but if you can do that with any component, chances are high that there will be some security holes in one way or the other. 2) Complexity! While it is possible to do that with most COM objects (ActiveX servers) there have very few people been able to make it work and even less to make it reliably work. The issue here is that you do need some form of security in place and getting that security configured just right is a very daring task. Even configuring Windows networking can be already an interesting task. In my experience, while I could see more or less any computer on the network in Windows 95 I have nowadays regularly problems to see computers that I have actually explicitedly setup with login and all to be accessible. And suddenly I can see them one day and suddenly they are gone. Rolf Kalbermatter

You are of course correct. I meant he could drop the pad string from the user friendly cluster, but of course it should be present in the low level cluster. And well about your latest remark, I do love to dabble in that low level stuff too, but yes it is always nice to return back to LabVIEW high level programming and concentrate on the real problem instead of making the memory ends meet everywhere and watch out about correct memory allocation and deallocation and never to access an invalid buffer . Rolf Kalbermatter

Congratulations and a success on your new endeavor! Rolf Kalbermatter

Actually I seldom can remember my dreams and if I do they are never about technical things. But I regularly get up the morning after a day of trial and error in getting something to work in either LabVIEW or a DLL and suddenly there is this idea in my head: "Hey why don't you try it in that way?" I'm pretty sure I have somehow worked on that at some point in my sleep and those ideas are often a bit unusual but most times they do work or at least get me a good way on to the real solution. Rolf Kalbermatter

If you can install them in LabVIEW 64bit and can open the VIs without getting a broken arrow then yes they have been obviously recompiled for Windows 64 bit. The LabVIEW Call Library Node can only access DLLs that are specifically compiled for the platform that LabVIEW is itself running on. It does not mean that that is a 100% warranty that there might not be still somewhere 32 bit limits in the IMAQ Visions software, but the DLL itself is certainly 64bit code. Rolf Kalbermatter

Wonder if it is an intricacy of the occurrences? At least in the beginnings all LabVIEW synchronization tools (queues, sempahores, etc) were based on occurrences and they do have a certain special behavior that they can initially trigger once, for occurrences that have been triggered by a previous execution of the code but not polled with a Wait on Occurrence. Rolf Kalbermatter

That would be a new feature then! Implementing a usable IP socket in hardware is anything but trivial and would easily eat up all your resources so there would be nothing left to do anything useful. The real time controller in the cRIO controller however implements a TCP/IP socket (obviously) so you could connect with that and have it pass the data by other means to the FPGA core. Rolf Kalbermatter