Rolf Kalbermatter

Of course not! ADO stands for ActivX Database Objects and ActiveX is a Windows only technology. Depending of the actual database server you want to access there are several possibilities but not all of them are readily doable in LabVIEW for Linux. If your database driver is implementing the whole communication directly in the LabVIEW VI level such as the MySQL driver here which access the MySQL server directly through TCP/IP communication, then you are fine. Accessing the unixODBC driver is another possibility which keeps the LabVIEW part independent of the actual database driver implementation. This project does provide such a LabVIEW library however, it is not always easy to get a working ODBC driver for a specific database server. Microsoft officially supports Linux clients with their latest SQL server but I have not tried that at all, and if you talk about the NI Linux realtime targets an additional problem is the architecture (ARM based for the low cost targets and x64 based for the high end targets) and the fact that NI Linux RT isn't a normal standard Linux system but in several aspects a slimmed down Linux kernel that some precompiled binaries may not work on, and to expect Microsoft to give you the source code of their SQL server libraries to compile your own binaries for a specific target is of course pretty hopeless.

Well, to claim that it could not have any effect on cRIO sales is rather bold. But my point was not that you can not do that, it's part of any competition that your product could have a negative effect on the baseline of another product. My point was that NI has a license deal with Xilinx which might contain wording about with what hardware the Xilinx tools that NI bundles with their LabVIEW FPGA Toolkit can be used and that might exclude non NI hardware. I'm not sure such limitations exist but it would not surprise me if it does and if it does, NI might be obligated to prevent use of the Xilinx tools included in the LabVIEW FPGA Toolkit with non NI hardware, both technically as well as legally, independent if they want to or not.

Right! I did check and when using shared reentrant clone VIs, then it also works in LabVIEW 2009. In my initial tests I did use the default preallcoated reentrancy of those VIs and that of course can't work as LabVIEW would then have to preallocate an indefinite amount of clones due to recursion and that would for sure crash! So LabVIEW 2009 it will stay!

Well recursion worked before but only if you opened a reference to the VI explicitedly. Since LabVIEW 2012 you can place a reentrant VI directly into its own diagram.

A colleague recently tried to use the OpenG Variant Configuration File Library and found that the loading and saving of more complex structures was pretty slow. A little debugging quickly showed the culprit which is in the way the recursion in that library is resolved by opening a VI reference to itself to call the VI recursively. In LabVIEW 2012 and later the solution to this problem is pretty quick and painless: Just replace the Open VI Reference, Call VI by Reference and Close VI Reference by the actual VI itself. Works like a charm and loading and saving times are then pretty much in par with explicitly programmed VIs using the normal INI file routines (cutting down from 50 seconds to about 500ms for a configuration containing several hundred clustered items). Now I was wondering if there is anyone who would think that updating this library to be LabVIEW 2012 and later would be a problem?

Definitely! NI licensed the Xilinx toolchain from Xilinx to be distributed as part of the FPGA toolkit and there will be certainly some limitations in the fine print that Xilinx requires NI to follow as part of that license deal. They do not want ANY customer to be able to rip out the toolchain from a LabVIEW FPGA installation to program ANY Xilinx FPGA hardware with and not having to buy the toolchain from Xilinx instead, which starts at $2995 for a node locked Vivado Design HL license, which I would assume to be similar to what NI bundles, except that NI also bundles the older version for use with older cRIO systems. So while NI certainly won't like such hardware offerings, as it hurts their cRIO sales to some extend, they may contractually be obligated to proceed on such attempts to circumvent the Xilinx/NI license deal, if they want to or not.

Hard to say anything conclusive without the ability to debug the libraries in source (and no I don't volunteer to do that, that would be the original developers task). Generally .Net only looks at the GAC and the current process' executable directory when trying to load assemblies. This has been done on purpose since the old way of locating DLLs all over the place in various default and not so default places has created more trouble than it actually solved. An application can then register additional directories explicitedly for a .Net context. LabVIEW seems to maintain seperate .Net contexts per application instance and a project is an application instance in LabVIEW, isolating almost everything from any other application instance eventhough you run it in the same LabVIEW IDE process. For project application instances LabVIEW also registers the directory in which the project file resides as a. Net assembly location. This may or may not have anything to do with your issue, but from the description of your issues, it could be that one of your assemblies is trying to load some other assembly and not properly catching the exception when that fails. But this is really all guesswork without a deeper look into the actual .Net components involved. If you can't get the original developer of the .Net component to look into this issue for you with a source code debugger, I see not a lot of chances to get this working.

Brian (Hoovah) has explained it all very well, including the option to use the loop conditional terminal to avoid the usually unneccessary looping through the remaining iterations.

There is definitely a change depending if you use a shift register or not for the error cluster with shift register without error before loop (n >= 1) n times do nothing n times do nothing error before loop (n = 0) error is visible after loop error has magically disappeared error in loop execution x of n 0 .. x -1 executes 0 .. n executes first error in loop is passed out unless you create an autoindexing error array, only the last error of the loop execution is passed out Generally only the purple situation in the loop without shift register for the error cluster is sometimes preferable above what the shift register would cause. The red ones are definitely not desirable in any code that you do not intend to throw away immediately.

The page you link to is not very detailed. But it says under Network Protocol: TCP/IP, HTTP, DHCP, DNS You can forget the last two, they do not mean anything for the actual accessibility, but HTTP means most likely that you can access a periodically refreshed still image (JPEG format) from it if you can figure out the right URL path. TCP/IP with H.264 hints most likely at support live streaming with the right driver. You will need to look for an IP Camera Driver for your OS that supports the H.264 compression. Alternatively you can most likely install something like https://ip-webcam.appspot.com/ to access at least the JPEG interface on your camera. This driver translates the JPEG images into a DirectX interface that you can then interface to with the IMAQdx driver software from NI to get the images into LabVIEW IMAQ.

Probably something with the .Net assembly search path in combination with some badly implemented dynamic linking. .Net by default only searches in the GAC and in the directory for the current executable for any .Net assemblies. LabVIEW adds to that the directory in which the current project files is located if you run the VIs from within a project.

1) is bad form. It will cause an invalid refnum (and empty arrays and strings and 0 integer and floats) after the loop if the loop iterates 0 times. And yes, even if you think it will never be possible to execute 0 times, you always get surprised when the code is running somewhere on the other side of the globe and you only have a very slow remote connection that makes life debugging impossible. 2) is the prefered way for me for any refnum and most other data. Anecdotely LabVIEW had some pretty smart optimization algorithmes in its compiler that were specifically targetting shift registers, so for large data like arrays and long strings it could make a tremendous difference if you put this data into a shift register instead of just wiring it through. he latest versions of LabVIEW do have much more optimization strategies so that the shift register is not strictly necessary for LabVIEW to optimize many more things than before. However the shift register won't harm the performance either and is still a good hint to LabVIEW that this data can be in fact treated inplace. 3) is simply ugly although it doesn't bear the problem of invalid data after a 0 iteration loop (but can potentially prevent LabVIEW to do deeper optimization which for large data can make a real difference). For error clusters 1) can be a possible approach although you still have the potential to loose error propagation on 0 iteration loops that way. You do need to watch out for additional possible problems when an error occures. One possibility is to simply abort the loop immediately which the abort terminal for for loops is very handy for, or to handle the error and clear it so the next iterations still do something. The least preferable solution is to just keep looping anyhow and do nothing in the subsequent iterations (through the internal error handling in the VIs that you call) BUT ONLY for For Loops!! Never ever use this approach in While Loops without making 200% sure that the loop will abort on some criteria anyhow! I've debugged way to many LabVIEW software where an error in a while loop simply made the loop spin forever doing nothing.

To my knowledge not beyond what you can get from the OpenG library. When I tried to do that I was looking for some further documentation but couldn't find anything beyond some tidbits in remotely related things in knowledge articles. So I simply gleemed through the different packages and deduced the necessary format for the .cdf ( component definition file ). Being an XML format file made it somewhat easy to guess the relevant parts. There is in newer LabVIEW versions an option to create an installation package for RT from an RT project which uses the same cdf file, but the creation of that file is of course hidden inside the according package builder plugin. If the purpose is to only create an installer component for a shared library then the files from the OpenG ZIP library should give some headstart. One problem you might have to solve is also to get the files into the RT Image subdirectory. Since it is inside the Program Files, your installer app needs to have elevated privileges in order to put it there. If you do this as part of a VIPM or OGP package file, then VIPM often is not started by default with such rights. I solved that by packing all the components into a setup file made with innosetup which will request the privilege evelation. Then I start that setup file at the end of the package installation and it then installs the components into the RT Image subdirectory.

LabVIEW doesn't deploy shared libraries to the embedded targets itself (except the old Pharlap based systems). So in my experience you always need to find a way to bring the necessary shared libraries to those targets yourself. One option is to just copy them manually into the correct location for the system in question (/usr/local/lib for the NI Linux RT based systems). Another one is to create a distribution package that the user then can install to the target through the NI Max Software installation section for the specific target. The creation of such a package isn't to difficult, it is mostly a simple configuration file that needs to be made and copied into a subdirectory in the "Program Files/National Instruments/RT Images" folder together with the shared library file(s) and any other necessary files. The OpenG ZIP library makes use of this last method to install support for the various NI RT targets.

Right, only works for byte arrays, no other integer arrays. And they forgot the UDP Write which is actually at least as likely to be used with binary byte streams. Someone had a good idea but only executed it halfway through (well really a quarter way, if you think about the Read). To bad that the FlexTCP functions they added under the hood around 7.x never were finished.

Wait are you sure? I totally missed that! Ok well: 2014: no byte stream on TCP Write 2015: no byte stream on TCP Write 2016: haven't installed that currently

I didn't mean to use shared libraries for Endianess issues, that would be madness. But data passed to a shared library is always in native format, anything else would be madness too. Strings being used as standard anytype datatype is sort of ok in a language that only uses (extended) ASCII characters for strings. Even in LabVIEW that is only sort of true if you use a western language version. Asian versions use the multibyte character encoding, where a byte is not equal to a character at all. So I consider a byte stream a more appropriate data type for the network and VISA interfaces than a string. Of course the damage has been done already and you can't take away the string variant now, at least not in current LabVIEW. Still I think it would be more accurate to introduce byte stream versions of those functions and drop them by default on the diagram, with an option to switch to the (borked) string version they have now. I would expect a fundamentally new version of LabVIEW to switch to byte streams throughout for these interfaces. It's the right format since technically these interfaces work with bytes, not with strings.

That's because you don't write shared libraries! Only the flattened LabVIEW formats use by default Big Endian. absolutely anything else is native byte order. And the only places where LabVIEW flattens data, is in its own internal VI Server protocol, when using the Flatten and Unflatten and the Typecast functions, or when writing or reading binary data to/and from disk. Still waiting for the FlexTCPRead and Write, that do not use strings as data input but directly the LabVIEW binary data types (and definitely a byte array instead of a string!! Same for VISA, the byte array I mean, strings simply do not cover the meaning of what is transfered anymore in a world of Unicode and Klingon language support on every embedded OS!!! ).

It's nitpicking a bit but the options for the Flatten (and Unflatten) functions are Big Endian (or network byte order, which is the same), Little Endian and native. Big and Little Endian should be clear, native is whatever the current architecture uses, so currently Little Endian on all LabVIEW platforms except when you run the code on an older PowerPC based cRIO. And LabVIEW internally uses whatever Endianess is used by the native architecture but its default flattened format is Big Endian. Those two are very distinctive things, If it would use Big Endian anywhere, it would need to convert every number everytime it is passed to the CPU for processing.

Well, I'm pretty sure that for DMA transfer you do need a physical memory address.The LabVIEW DSNewPtr() function allocates a chunk on the process heap, which is a virtual memory area for each process. Between this virtual adress space and the actual physical address is the CPU MMU (memory management unit) which translates every address from the virtual memory to the actual physical memory address (and in the case of already cached memory locations actually, this step is skipped and directly translated to the cache memory location). The DMA controller only can transfer between physical memory addresses, which means for DMA transfer all the cache lines currently caching any memory that belongs to the DMA transfer block need to be invalidated. So you first need to lock the virtual address block (the DMA controller would get pretty panicky if the virtual memory suddenly was moved/paged out) which will also invalidate the cache for any area in that block that is currently cached and retrieve its real physical address. Then you do the DMA transfer on the physical address and afterwards you unlock the memory area again, which also invalidates the physical address you previously got. Incidentially the services you need to access to do physical address translation and locking are all kernel space APIs. VISA comes with its own internal kernel driver, which exports functions for the VISA layer to do these things but performance suffers considerably if you do it this way. The alternative however is to have to write a kernel driver for your specific hardware. Only in the kernel driver do you have direct access to physical memory translation and such things, since these APIs are NOT accessible from the ring 3 user space, normal Windows processes are running in. And yes, Windows limits the size of blocks you can lock. A locked memory area is a considerable weight on the leg of every OS, and in order to limit the possibility for a kernel driver to drown the OS for good, this limitation is necessary. Otherwise any misbehaving driver could simply DOS the OS by requesting an unreasonable big block to be locked.

Most of the database work we do is SQL Server, occasionally Oracle for specific customers and we normally use our own Database Toolkit. Difference to the NI database toolkit are Express VI based configuration wizards for the queries and transparent support for multiple database drivers such as MS SQL Server, Oracle and MYSQL, (MS Access too, but that hasn't been used in ages, so I wouldn't vouch for its spotless operation at this point). In addition I have my own ODBC based API that I have used in the past. I'm still considering about incorporating everything into a unified interface, likely based on a LabVIEW class interface, but proirity for that never seems to make it into the top 5.

Actually btowc() is the single byte version of mbtowc(). Both are single char, but the first only works for single byte chars while the second will use as many bytes from a multi byte character sequence (MBCS) as are needed (and return an error if the byte stream in the mbcs input does start with an invalid byte code or is not long enough to describe a complete MBCS character for the current local. mbstowc() then works on whole MBCS strings while mbtowc() only processes a single character at a time. Please note that a character is not a single byte generally although here in the western hemisphere you get quite far with assuming that that is the case, although it's not quite safe to work from. Definitely on *nix systems which nowadays often use UTF-8 as default locale, you automatically end up with multibyte characters for those Umlaut, accent and other characters many European languages do use. Windows solves it differently by using codepages for the non-Unicode environment, which for western locales simply means that for extended characters the same byte means something different depending on the codepage you have configured. But even here you do need MBCS encoding for most non western languages anyhow UTF-8 to UTF-16 conversion is a fairly straightforward conversion, although the simple approach of some bitshifting only, could end up with invalid UTF-16 characters. A fully compliant conversion is somewhat tricky to get right for yourself as there are some corner cases that need to be taken care of.

Well Windows 3.1 was not fully protected mode anyhow. Your LabVIEW process could kill your File Manager (the predecessor to your good old File Explorer for those young sports knowing Windows 3.1 only from hairy tales of others) quite easily. And multitasking was fully cooperative, if an application forgot to call the GetMessage() API (or at least the PeekMessage() call) in its message loop (the root loop in LabVIEW and the thread_0 or UI thread too) then all Windows applications were hanging for good and only some kernel driver stuff would still be working in the background. To be fair though MacOS Classic was about the same . That about sharing globals between LabVIEW executables does sound a bit strange to me though. What you could do is referencing VI files (and gloabals) in an executable as if they were VIs in an LLB (which they actually were back in those days). But that wouldn't really share the dataspace, only create a copy of the VI and its dataspace in the other application. There is no safe way to abort a thread that has been locked by an external DLL and resume operation from just after calling that DLL. That DLL could have been suspended in a kernel call at that point (and quite often that is exactly where the DLL is actually waiting) and yanking the floor out under its feet at that point could leave the kernel driver in a very unstable state that could simply crash Windows.

Well not necessarily exactly the same CLR version but there has been a change somewhere between 3.5 and 4.0 of the CLR which makes this usually break. Both the calling application, here LabVIEW, and your callees need to be on the same side of this limit. LabVIEW until 2012 or so was loading by default CLR 3.5 or lower and newer LabVIEW versions load the CLR 4.0 or higher by default. If your assemblies are created for a different CLR version you either have to recompile them to use the version LabVIEW is using or you have to create a manifest file for LabVIEW to make it load a different CLR when initializing the .Net environment. The exact procedure for creating that manifest file are detailed here. Things get hairy when you have to incorperate multiple mixed mode assemblies that use CLRs from both sides of the 4.0 version limit.

If the library is written and compiled as a managed .Net assembly you do not use the Call Library Node to call its methods, but the .Net palette instead. While a .Net assembly has a DLL file ending, it is not a classical DLL at all, and only the .Net CLR has any idea how to load and reference that.