Jump to content

smithd

Members
  • Content Count

    718
  • Joined

  • Last visited

  • Days Won

    42

smithd last won the day on May 21

smithd had the most liked content!

Community Reputation

146

About smithd

  • Rank
    The 500 club

Profile Information

  • Gender
    Not Telling

LabVIEW Information

  • Version
    LabVIEW 2013
  • Since
    2011

Recent Profile Visitors

2,810 profile views
  1. I've definitely used it, although we ended up going with a different db so the code never got used for real. I think I had tried it on lvrt but I can't really remember. I tend to think that talking to a central db from an rt target tends to break the nicely distributed nature of the systems and so I'm more likely to use your sqlite on rt, but I get that for test systems and the like (now that PXI RT Linux is a thing) might be more likely to talk directly to a postgres database.
  2. https://stackoverflow.com/questions/39576/best-way-to-do-multi-row-insert-in-oracle
  3. i think if you put the img display in snapshot mode its synchronous? I agree that imaq needs refs, but why does it need named refs? Thats the part thats horrifying
  4. Yes, I don't really care about that, and I will use block diagram cleanup until its pried from my cold dead hands 👻 Some of the key parts (like the engine) are relatively neat (by my standards) but due to the complexity its definitely still a hot mess. And of course a lot of the code dealing with all of the data types is scripted because aint nobody got time for that. Your other comments are fair though, some definite mistakes were made in the design, but all told I think it does a decent job. Yeah, I made an aborted attempt (https://github.com/LabVIEW-DCAF/ModuleInterface/tree/StreamingAndEvents and https://github.com/LabVIEW-DCAF/ExecutionInterface/tree/StreamsAndEvents) but...then I left NI. The nature of labview merging is such that those branches are probably now useless edit: theres probably a few implementation-side branches too like https://github.com/LabVIEW-DCAF/StandardEngine/tree/StreamsAndEvents
  5. Labview doesn't provide a way to check the status of the TCP connection except by trying to use it. Serial modbus has no physical way to check the connection except by using it. In both cases you need to use it to see if it still works. On the master (client) side you will see any of the TCP error codes (56, 62 and 63 being the most common as I recall) for the TCP master. For serial masters, you will only ever see 56. I suppose some VISA-specific codes are also possible, like if there are parity bit errors or if you're using a usb-serial device that gets unplugged, that sort of stuff. Modbus protocol errors are - 389110 as mentioned above. On the slave (server) side you will never see an error from the data access methods because the access is local. You can check (via a property node, I think) on the status of all connected masters (clients) for TCP. Serial is 1-1 and has no concept of a connection, so I think it just tells you the last error to occur for the serial comms process.
  6. cRIO is all linux, PXI now supports linux: https://www.ni.com/product-documentation/55164/en/
  7. I wouldn't do this. Its probably ok in this limited case, but its possible to make labview crash in this way. A better route is the variant, which has the same capabilities (cast to an opaque untyped blob and back again) but without the danger.
  8. Doing a quick search, C++ doesn't permit access scope for the class itself -- only at the member level. In other words the class itself is always public
  9. As described, anyone can take your DVR, unbundle it, and get access to the class. Since this is possible, and the class is private, it must be blocked. Technically this doesn't make much sense for labview classes since their data is private by default. Makes more sense for clusters, where enclosed data is private, so maybe thats why. You can make the methods of the class private, but the class itself must be public. Or, you could use a DVR of the base labview object and then cast it when you use it, inside of your library.
  10. Depends on the database. For example, oracle does not support multiple inserts in a single query like that. Instead you'd have to use: INSERT INTO T_Column (C_Name , C_Status) VALUES('21' , 'Not realised'); INSERT INTO T_Column (C_Name , C_Status) VALUES('22' , 'Not realised'); On the one hand this sucks, but on the other hand if you're using oracle this is probably the least of your worries. On a related note, it looks like you are manually generating sql queries. While fine for development, its generally recommended to use parameterized statements to help avoid sql injection attacks.
  11. afraid not, I moved on to 2017. At this point I think your best bet is to use a pre-2017 version (pre-vim). You can backsave but the vims make it annoying. If you are windows-only, I think the labview runtime now supports several versions back and forth, so it might be possible to build the 2017 library into a packed library (very much like a dll, but pure labview code) and reference that. Probably not worth it though. 2015 is 4 years old at this point, might be worth investigating an update.
  12. the terminology NI was using a few years ago was tag/stream/message and i believe the descriptions are as follows: messages have a non-fixed rate, mixed data types, and should generally be as lossless as possible with minimal latency, with the note that anything requiring confirmation of action must be request-response which takes you down the rabbit hole of idempotence (ie what happens if the response is lost, request is reissued -- does the customer get 2 orders?). Messages are usually 1:N (N workers for 1 producer) or N:1 (N clients for 1 process), but this isn't required. streams have a fixed rate, fixed type, and generally latency isn't an issue but throughput is. Losslessness is a must. Usually 1:1. tags are completely lossy with a focus on minimal latency. The addon to this would be an 'update' which is basically a message oriented tag (eg notifier, single element queue). Usually 1:N with 1 writer and N readers. all three overlap, but I think these three concepts make sense.
  13. Of the messaging things plain queues should be the fastest message-oriented option because everything else (I think) is built on top. Notifiers, channels, etc use queues. All these options are pretty quick. >Last I remember reading, user event queues rely on some of the same underlying bits, but the UI-oriented and pub-sub nature of the code makes them a bit slower. Still generally fast enough for anything anyone ever uses them for. >>User events are completely nondeterministic (every option in this category is nondeterministic technically, but user events behave like garbage if you stress them). Property nodes obviously require locking the UI thread and suck, but control indices are sufficiently fast for most anything. If you eliminate the update-oriented part -- just sharing scalar values in other words -- then the fastest would be a global (requires a lock for write but I think the read side doesn't), then a DVR in read-only mode, then a standard DVR or FGV implementation (both need to lock a mutex). These are all faster than the message oriented variations, obviously, but thats because you get less than half the functionality.
  14. Its similar to flattening a cluster, except its cross language. It accomplishes this by having scripts which take a message definition and generate code in that language. This makes it easy to send a protobuf message, which might be represented in labview as a cluster*, to C or java or python or go or wherever. Its primary benefit over something like json is a slightly more extensive type system and speed. This won't get you any of what I described but if you just need super basic support for generating a valid message manually: https://github.com/smithed/experiments/tree/master/Protocol Buffers It would need a ton of work to actually support scripting. Doesn't seem like there is enough of an advantage. *I'm pretty sure it always has to be a class actually due to things like optional data values.
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.