Deterministic CAN Frame to channel conversion

Hi, I need to create a CAN logger which should record (in TDMS format) and show in real time (in a mixed signal graph) several channels in deterministic mode.
Using an interface wich supports the Channel API (such as NI PXI-8464) it is all right and the software works properly.
The problems appears when the aquisition is done through a NI USB 8473, doing the frame to channel conversion with the two virtual channels (CAN256 and CAN257). The conversion is done in the way shown below:
where in the CAN256 i transmit in "timestamped mode"
While the time goes on, the logged signal is more and more delayed respect the real one until the buffer fills and an error is generated.
What i need is a Frame to Channel conversion wich keeps deterministic, also with a small constant delay.
Any solution?
Thanks a lot
Fabio

Hello Fabio,
Usign the virtual ports for frame to channel conversion is not very efficient. I would suggest using the frame to channel conversion library.
Let me know if you have any questions about it. Have a great day.
O. Proulx
National Instruments
www.ni.com/support

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Advanced CAN Frame to Channel Conversion: Error with LV 8.5.1

Hello!
I´ve tried to read in a DBC-file with the "Advanced CAN Frame to Channel Conversion Example" on a LabVIEW 8.5.0 system and it works fine.
On a LabVIEW 8.5.1 System I get the error:
Scan From String (arg 6) in CAN FtoC Parse Channels and Mode.vi->CAN FtoC Parse CANdb Messages and Channels.vi->CAN Channel Data Import.vi
Does anybody know a solution for this error?
Thank you for your help,
demo66
regards,
demo66

Hi!
It is a problem of localized decimal point.
In a german Windows, LabVIEW will use Komma as decimal point.
So the Scan From String.vi will convert string 0,21 in a double but not 0.21. From the file dbc you receive the values with period "." that's why it create the error 85.
You have 2 possibilities: change the localized decimal point in LabVIEW (Tools -> Options) or you say to the Scan From String.vi to use "." as a decimal point.
Go to CAN FtoC Parse Channels and Mode.vi and search the 2 Scan From String.vi
Add at the beginning of the Format String %.; so that the format String will use the "." as decimal point (see Attachement).
After that the example will work.
Best regards
Ken
Attachments:
Scan From String.jpg ‏51 KB

CAN Frame to channel conversion using CVI

Hi,
I am using USB-8473 can bus modules in a project. I would like to display the channel data by using the Frame to Channel conversion library. Is there a version that can be used with CVI? I am using CVI 9.1
Thanks
John

Hello John,
I do see what you mean, the VIs actually just call into a C dll. I dowloaded to the Library after reading your post and opened up the VIs. It looks like each is just a small wrapper around Call library funciton node. It is definately silly that the VIs are so well documented but not the functions of the dll itself. Based on browsing a few of these VIs, it would be pretty easy to write the wrapping code in C and call all the same functions of frchconvlib.dll.
I will look into whether this library was written by a third party or NI, and if its NI property I would like to expose the dll itself to users like yourself.
I do apologize that this is the only current solution. I will let you know what I find out.
This kind of feedback it important to receive, so thank you for voicing you concern.
Best,
Anna K.
National Instruments

CAN Frame to Channel Conversion Library

Hi,
Is it possible to use this DLL with CVI? If so, is there any example code or a user document?
Cheers,
John
John C
Solved!
Go to Solution.

Hi JGC
Unfortunately this Library is only meant to be used from LV and LVRT, an equivalent Library does not exist in CVI.
With that said, you may be able to dig into the LabVIEW VI's of the Frame Channel Conversion Library and pull the function prototypes from the Call Library Function Node on the block diagram of each one. With this information, you could call the functions from the dll (usually located here: C:\Program Files\National Instruments\NI-CAN\CAN Frame Channel Conversion Library 1.0.2\Drivers) from within C.
Kind Regards
Chris
Chris | Applications Engineer NIUK

Advanced CAN Frame to Channel Conversion Reference Example

Hi!
I wonder if any of you guys can help me converting this example into LV7.1.
The example is under:
http://zone.ni.com/devzone/cda/epd/p/id/5826
Thanks in advance!!!
Ogulcan
Solved!
Go to Solution.

Ogulcan,
The example that you are asking for is built with a different version of the NI-RIO and Real-Time drivers. Downgrading this example would require a system with LabVIEW 8.5 or 8.6 with the most current RIO and Real-Time drivers, and a system with LabVIEW 8.0 and an older version of the RIO and Real-Time driver. It may also require a third system set up up LabVIEW 7.1 and even older versions of the RIO and Real-Time drivers. The changes in these drivers and the included VI's since LabVIEW 7.1 would also likely make this example not work with LabVIEW 7.1, which may be why it was posted for LabVIEW 8.5.
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CAN Frame Channel Conversion Library

Hello, I am trying to use the attached ncd file to read from a Series 2 board via the Conversion library but it's not working. I can load the ncd in Max and it read the channel fine.
What would cause this?
I am using the sample vi USBCANBasicInput.vi. It seems imposible to debug because it uses a dll for everything.
I am using version 1.0.3.
There are extended CAN messages.
Thanks in advance,
Dustin
Solved!
Go to Solution.
Attachments:
USBCANBasicInput.vi ‏44 KB
atc.zip ‏1 KB

Dustin,
It was a pleasure speaking with you on the phone today.
It seems that the problem was in using extended arbitration ID's with the Frame Channel Conversion Library. Here are some examples that show how to use this library with extended arb ID's.
http://decibel.ni.com/content/docs/DOC-6793
http://decibel.ni.com/content/docs/DOC-6792
http://decibel.ni.com/content/docs/DOC-6055
Regards
Peter Flores
Applications Engineer

CAN Frame Signal Conversion With XNet

When dealing with CAN, most new developer struggle with the Frame and Channel (or Signal) conversion. Developers are trying to get away with using the cheapest CAN hardware, and as a result are opting to not use XNet hardware but instead use things like the USB 8473, or using non-NI hardware like the ValueCAN by Intrepid, or using Vector hardware, or CAN to serial adapaters. The problem with all of these is you generally just read and write frames which is the raw form of CAN. When using these cheap devices you can't ask the CAN bus what the signal Bus_Voltage is, instead you need to perform a frame read, find the frame associated with the signal, then pull out the bits for that signal, then scale the signal based on the signal selected.
All of this is doable but a pain and can be very custom. That's one reason NI came out with the Frame Channel Conversion Library. This library converts from Frames to Channels using an industry standard CAN database file. The problem with this library is it hasn't been updated in 5 years, and has known issues which likely will never be fixed.
NI has since come out with XNet which supports reading and writing signals on XNet hardware. The XNet drivers also support converting Frames to Signals without needing hardware at all. This conversion has several limitations, and really only works for getting the latest value for a signal, not all values. And in addition to that if the signal was never seen, the value will be the defaul value for that signal, not NaN.
So I wrote a wrapper around the XNet conversion library to handle going from signals to frames, or from frames to signals. Anyone looking to use a DBC file, on hardware that only supports frame API should use this conversion library, or at least use the XNet conversion sessions.
CAN Frame Signal Conversion Using XNet
Unofficial Forum Rules and Guidelines - Hooovahh - LabVIEW Overlord
If 10 out of 10 experts in any field say something is bad, you should probably take their opinion seriously.

Hello Hooovahh,
Nice work . It’s very useful.
I’m also converting CAN Raw data to Physical values in my project. Yes, your correct XNET APIs have some limitations. as you mentioned, there is one more limitation I found,
If your Message Data length (Payload) is 4 Bytes (example) and other CAN Frames are having more than 4 Bytes then its throwing Error (Error Code -1074384737).
While converting CAN Frames to signals, we will get different Payloads but, our selected signal message have 4 bytes then XNET will gives an error (at the time of Data Conversion).
As per attached Snap, My Signal is related to IDxBB and I’m sending two different Frames then XNET will not convert.
Hooovahh Wrote:
NI has since come out with XNet which supports reading and writing signals on XNet hardware. The XNet drivers also support converting Frames to Signals without needing hardware at all. This conversion has several limitations, and really only works for getting the latest value for a signal, not all values. And in addition to that if the signal was never seen, the value will be the default value for that signal, not NaN.
When we will send Frame by Frame then we will get all values (not only recent values). XNET will take previous value (if data is not present for Next iteration)
Please check this snippet for all values & NaN Display.
Munna

Frame Channel Conversion Library for LabwindowsCVI

Could someone help me to identify Frame Channel Conversion Library for LabwindowsCVI. I found a library for labview and it is working fine with my USB8473. But i really need to get it working with Labwindows. Have anyone tried to access the frchconvlib.dll from labwindows? Thanks in advance.

Unfortunately, the C API is not documented, nor is it stated as a supported interface.
With that said, you may be able to dig into the VI's of the Frame Channel Conversion Library and pull the function prototypes from the Call Library Function Node on the block diagram of each one. With this information, you could call the functions from the dll (usually located here: C:\Program Files\National Instruments\NI-CAN\CAN Frame Channel Conversion Library 1.0.2\Drivers) from within C.
Let me know your thoughts and if you have any success.
Regards,
Peter Flores
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Frame Channel Conversion Library

Hello everyone,
I'm currently using the Frame Channel Conversion Library (downloaded on the NI Site) and I noticed that there are troubles when using a.dbc containing channels with "scaling factor".
When I convert the .dbc in the .ncd format, the scaling factors are correctly translated and then correctly interpreted by the DLL of the Convert Frame to Channel.vi, but when I use directly the .dbc in the same function (i.e. Add Selected Channels From File.vi), I always get 0 in the scaled data.
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Thanks in advance.

This could be an issue of using extended 29 bit IDs with the conversion library. If you have extended Ids with your signal database, the NI-CAN driver allways expects to see the 30 th ID bit set additionally if you like to transmit an extended ID and you have to remove the 30 th bit if you provide the ID for the conversion VI. See the attached pictures for how to remove and add the 30th bit for NI-CAN.
This is only necessary if you use dbc files. The max export to ncd removes the 30th bit automatically.
DirkW
Attachments:
30thbit_add.jpg ‏49 KB
30thbit_removal.jpg ‏25 KB

Can PCM multi-channel wav (not DD or DTS) be sent over SPDIF

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Here is short demonstration of SPDIF transmission of 24bit/96 kHz between two sound cards with and without "bit accurate for playback" enabled:
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How can I enable/disable the transmission of a can frame? (filter etc...)

Hello,
I use the CAN
Transmit-periodic.vi in LV 8.5, I want to enable or disable the
transmission of a frame without stop the loop of my VI, does it exist
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Hi there
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