Jump to content

Porter

Members
  • Content Count

    143
  • Joined

  • Last visited

  • Days Won

    16

Porter last won the day on August 17 2018

Porter had the most liked content!

Community Reputation

40

1 Follower

About Porter

  • Rank
    Very Active

Profile Information

  • Gender
    Male
  • Location
    Canada

LabVIEW Information

  • Version
    LabVIEW 2017
  • Since
    2008

Contact Methods

Recent Profile Visitors

2,645 profile views
  1. @Masony, something like this?
  2. I thought that it would be nice to extend the muParser library's functionality to include automatic CVT tag lookup. This means that if you input an expression that contains CVT tag names as variables, their values will automatically be substituted during eval. This new CVT expression parser IS AN expression parser. So I tried to make a child of the mupExpr class. Who's silly idea was it to pass this class by reference?! LabVIEW doesn't support dynamic dispatch on class DVRs. So I've re-worked the mupExpr Class to wrap only the muparser handle (hParser) in a DVR. This gives a similar protection as wrapping the class in a DVR but allows us to pass the class by value instead. If anyone objects to this change, please shout out now before I commit changes to github. The code is attached, with an example: NICVT Expression Test.vi You need to install NI Current Value Table v.3.3.0 before opening the project. NICVTExpr.zip
  3. Since your input registers are contiguous, I would suggest reading all of them with one call of read input registers. See attached. Modbus Read Waveform.vi
  4. How much data are you transferring? For example, if you are reading 1000 input registers, one register at a time, then you can't expect to get a sample rate of 100ms. Screenshots or sample code would be useful if you are looking for help. Are you using the Modbus Comm Tester?
  5. Just in case anyone is still interested, the source is now available on github: https://github.com/rfporter/SET-Toolkit
  6. It should show an error on every subsequent read... but it doesn't: It just keeps going as if nothing is wrong.
  7. His code has not fixed the issue yet. It does catch the error, as did Plasmionique Modbus Master, but it is up to you to catch the error and reset the connection. If you don't reset the connection, this can happen: Yikes! No errors being reported and read register 0 is returning the value for register 1. Tanner's proposed fix works. I implemented it in the Plasmionique Modbus Master. With it you can have multiple pending transactions. The responses will be matched up with the requests using the transaction ID. TCP Test.vi
  8. Hah. I didn't see that. I was looking somewhere else. But anyway, I don't see a case where you would only get a LF. In the ASCII protocol, a lone LF should never be sent within the message. And if, for whatever reason, a bit flips to make an LF, then hopefully the error would be caught by failing the CRC check.
  9. For comparison, I copied the CRC calculation from the modbus spec. It's slightly faster (when run on my computer) than your method. I'm not exactly sure why though. And it uses less memory (512Bytes for LUT instead of 131kBytes). crc bench.vi CRC16_Modbus.vi
  10. It is thread safe as long as you use the same instance of serial master when communicating with multiple slaves on the same bus. I finally took a look at the code. I have a couple comments/questions: Serial Shared Components.lvlib->Configure Serial Port.vi: Case structure for number of stop bits. I suggest having some override for this. Maybe have a property node for the stop bits setting. I've come across a number of situations where I have needed RTU with no parity and one stop bit. RTU Data Unit.lvclass->Calculate CRC.vi: I think that there is a more efficient way to calculate the CRC using a lookup table. I'd be happy to share it when I get around to implementing it on Plasmionique Modbus Master. Serial Shared Components.lvlib->Serial Read.vi: I don't like the idea of polling the bytes at port every 8ms. Why not just read the specified number of bytes and let VISA handle the timeout? Serial Shared Components->Serial Read to CRLF.vi: Why not just read until LF (let VISA read take care of this)? ASCII Data Unit.lvclass->Read ADU Packet.vi: Why is start character written to request unit ID of Serial Data Unit? Shouldn't it be the unit ID? IP Data Unit.lvclass->Read ADU Packet.vi: Transaction ID mismatch will discard the packet. What will happen on a noisy network connection with multiple transactions being sent out? See: https://github.com/rfporter/Modbus-Master/issues/1 Why does TCP Master/Slave need Protocol Read to CRLF.vi? TCP_NODELAY.vi: Cool... Was this ever used & tested?
  11. I actually still use the OpenG ini library for a lot of my config files. As I recall, it's output was a bit more human-readable compared to the MGI ini format. Recently I've started to look at TOML as a possible replacement: https://github.com/erdosmiller/lv-toml Of course JSON or XML could also work very well but they look a bit more intimidating to the non-technical user.
  12. Plasmionique Modbus Master cannot act as a slave. NI Modbus Library contains a good slave for testing purposes: https://github.com/NISystemsEngineering/LabVIEW-Modbus-API
  13. At the time, I was using the actor framework for a large project. I had multiple com ports and multiple devices on each com port. I decided to have an actor per device. Each modbus device actor would build its own modbus instance from the device's configuration file. Since the modbus instances were thread safe, I didn't have to worry about sharing a com port with multiple devices. Devices on the same com port simply wait in a FIFO queue for the port to be available. I could have instead implemented a modbus master actor and spun up one of these actors per com port. The device actors would then have to send/receive their modbus data through the modbus master actor running on their com port. This way, the modbus master library doesn't need to be thread safe (in terms of shared com port), but I found that it added an extra layer of complexity. I prefer to handle serial communication in my hardware abstraction layer rather than my application layer. Otherwise the device's driver would be tied to the actor framework and would be difficult to reuse for other projects
  14. NI Labs Modbus API is now on GitHub! Password protection of VIs has been removed. https://github.com/NISystemsEngineering/LabVIEW-Modbus-API
×
×
  • Create New...

Important Information

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