NI-CAN Frame API: Variable Periodic CAN Object

Hi,
I am developing an application that send CAN messages with NI-CAN Frame API.
Some of my messages have specification of variable periodic where
- On idle, NI-CAN will periodically send the message at 100ms period of last message
- On a user input, it will send at period of 10ms for short period (200ms) and back to idle.
In CAN Object Configuration, as I put period to 100ms, The idle data is correct but when I need to send the user input, the data is sent using the period of 100ms as well. If I put period to 10ms, even during idle data, the message are sent every 10ms.
If I configure the CAN Object's communication type to transmit data by call, the data is only sent once and not periodic.
Does the NI-CAN Frame API supports variable periodic CAN Object?
Is there suggested way to have such a message?
- Meadow -
LabVIEW 7.0 - 2011, Vision, RT, FPGA
TestStand 3.0 - 4.5

Hello,
In general, a clear function will flush all data associated to a task. Have you tried using nctClear()? Although this is a legacy driver so that may not be the case…I found this article that explains how to reset the device (same functions are available in the C API, see manual) which can help but according to this thread is not a 100% effective due to its limitations. Nevertheless, is better than nothing.
I hope this helps
Alejandro | Academic Program Engineer | National Instruments

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CAN periodic transmit message with different modes using Frame API's

I want to transmit a CAN message periodically using Frame API's. I am able to send messages which dont have modes inside the message. For some messages having multiplexer in ".ncd " files and inside that multiplexer having different modes. Now in order to send all the modes of that message periodically by configuring them once by using Frame API's i did not find a way. I am able to send messages but the last updated mode is only sent periodically. Is there any way that CAN message having different modes can be sent periodically, updating all modes periodically automatically using Frame API's.

Hello Kpraveen,
You could set the period for N*Period, N being the number of modes. You just need to make sure your application changes the modes fast enough to update each periodic frame.
For example, say you have 2 modes and the frame's period should be 10ms. That means that you would like that frame to go out twice every 10ms, updating mode 1 and then mode 2. So, that means that the frames period can be 5ms.
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O. Proulx
National Instruments
www.ni.com/support

Filtering can frames with frame api (part 1)

Hello,
I have problems to understand the filter techniques in the frame api for C/C++.
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m_attrList[0] =       NC_ATTR_BAUD_RATE;
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m_attrList[1] =
NC_ATTR_START_ON_OPEN;
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m_attrList[2] =       NC_ATTR_READ_Q_LEN;
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m_attrList[3] =       NC_ATTR_WRITE_Q_LEN;
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m_valueList[4] =    NC_CAN_ARBID_NONE; //handle all
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m_attrList[6] =       NC_ATTR_COMP_XTD;
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m_attrList[7] =       NC_ATTR_MASK_XTD;
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CANObject
- up to now all fine
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(...please continue on part 2)

for answer see part 2
DirkW
Message Edited by DirkW on 01-10-2006 04:01 PM

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: HI,
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Well, everything is in the Subject : "Baud Rate" AttrId not found for CAN frame API's ncGetAttr and ncSetAttr
Although it is listed in the LabVIEW Documentation, it is not in the enum's items gotten from `right click` -> `create` -> `contsant` on their `AttrId` connector.
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You are quite right about the ncGetAttr.vi however the ncSetAttr does have a Baud Rate item if you scroll further down.
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Hi,
I'm using a PXI 8461 to control 2 CAN-bus lines.
When I start the bus monitor in MAX, both work correctly (frames are coming in).
But I wasted a day now to try to make both lines work in my app.
I'm calling ncConfigCANNet.vi and ncOpen first with CAN0, then with CAN1. ncOpen with CAN0 gives me an objHandle, but when I cann ncOpen with CAN1 after that, I get objHandle=0 but no error!
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NI-CAN 2.7.2f2
LV 8.5.1
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100g Ritter Sport Chocolate per hour
-DB
Solved!
Go to Solution.

If you look at this vi from the NI-examples:
Multiple CAN Cards Frame API Single DAQmx Card Input.vi
this is what I'm doing. As I said, this example is behaving the same way as my program. CAN0 responds, CAN1 doesn't.
MAX is closed. And even if there was some other program allocating CAN1 there should be an error. But ncOpen runs without error and still returns null. Just like calling it with an error on the "Error In" terminal... but I have no error there.
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-DB

Is NI-CAN v2.3 & NI PCI-CAN/XS2 with Frame API Thread Safe?

Hi, I'm downloading a file from the host computer to the modules. When I downloaded the data to the four module at the same time (with 4 threads), I'm getting communication failure ~ 20% of the time. When I synchronized the software, so it will download two modules at a time (using one port from each card at a time). The communication failure disappeared. I just wonder if the NI-CAN software & PCI-CAN/XS2 are thread-safe. I'd appreciate if anyone have any suggestion.
Information of the software & hardware
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- OS: Windows 2000
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The NI-CAN software does support threads. What's the specific error
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CAN Channel to Frame API

Hi All,
In a bit of a jam...we're using CAN channel api to manage a few functions of a piece of hardware thats on a CAN bus. Works great. Code is attached as a picture.
We are duplicating the system and have loaded the entire PC up and had to resort to a USB based CAN card that doesn't support channel API. Yeah bad.
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Talk to me like a little kid on this one, CAN at frame level is completely new to me.
I am able to watch all the data on the bus via MAX and the bus monitor, so I thought this would be more a labview board type question.
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LV7.1, LV8.5
Attachments:
CANHelp.PNG ‏18 KB

Hi
I didn't know there is a genuine conversion library
I've been recently doing some work as vacation replacement for a colleague that had a CAN interface for a data logger.
Since the channel API is relatively slow the concept was to log everything in frame API and later convert it to channel by passing it through a virtual CAN bus. This is provided by NI at "ports" 255 and 254 or something like that. You should check the help docu which is not too bad.
The only caveat was that the simulated CAN does by default also simulate delays and transmission time on the bus, you have to explicitly set this to no or zero or something. On TX and RX this works differently one is a property node the other a method. and you have to be precise with the sequence of doing what.
But in the end it worked.
Unfortunately the program is now on the customer's PC. So I cannot be any more precise on the how-to-dos.
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7.1 -- 2013
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Where can I find the Frame API for CAN

Hello,
I'm fairly new to labview and working with CAN Buses. I am trying to read messages from a CAN Bus. I downloaded some examples from the web site, and I ran the programs, but it seems like I am missing a bunch of VI files for example, "ncConfigCANNet.vi" or "ncOpen.vi", all of which are part of the Frame API. I am wondering, where I can get these files, as I have been searching all over the web only to find nothing.
Thank you very much for any responses!
Solved!
Go to Solution.

Have you installed the NI-XNET driver ? If yes, have you checked the NI-XNET Compatibility Library for NI-CAN ?
See here for more details.
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847x USB-CANにおけるFrame APIのサポート内容

　USB CANインターフェース USB-8473 と Frame API for C を使用してプログラミングしていますが、まだ対向デバイスがないので実地にいろいろと確認できない状況です。
http://digital.ni.com/public.nsf/allkb/E1A44077DA6C819186257288006B76D7
上記ページに847xでのFrame API 制約等の記述がありますが、関数名等が NI-CAN Hardware and Software Manual Capter11 と一致しておりません。少し内容が古いのかとも思われますが、現行2.5に一致するものをご紹介いただけたらと思います。
基本的には、ネットワークオブジェクトのサポートだけで、CANオブジェクトはサポートしていないと理解しておりますが、細部に関して自信が持てずにおります。
１）
ncConfig() で指定可能なパラメータがボーレートとStartAtOpenの二者のみとのことですが、例えば NCATTR_WRITE_Q_LEN は、なにかデフォルト値が適用されるということでしょうか?
ncWriteMultはタイプスタンプ以外使用可能と思いますが。
２）
ncCreateNotification() は制約無しでしょうか?
３）
ncWaitForState() は、現在でもncRead/WriteMult() をサポートしていないのでしょうか?
以上、USB-CANに関する質問です。

平素よりNI製品をご利用頂きまして誠に有難うございます。
日本ナショナルインスツルメンツ技術部の宮本と申します。
お問い合わせの件に関しまして以下の通り回答いたします。
ご投稿いただいたリンク先の関数名がNI-CAN Hardware and Software Manualと一致していないのは、これらの関数名がLabVIEWで使用されている関数名になる為です。Frame API for Cをご使用いただいておりますので、大変お手数ですがマニュアルのIndex(I-Nの項目)をご参照いただき、どのC関数がどのLabVIEW関数と同様の働きをしているかご確認いただく必要がございます。例えば、CのncCloseObjectは、LabVIEWのncCloseに相当します。また、CのncOpenObjectは、LabVIEWのncOpenに相当します。
1)ncConfig関数での設定なのですが、以下ディレクトリのサンプルプログラムをご参照いただければ設定をご理解いただけると考えております。
C:\Program Files\National Instruments\NI-CAN\MS Visual C\Frame API examples\CAN Receive
2)ncCreateNotification関数は、上記リンク先、またマニュアル(11-39)にてサポートされている関数として記載されておりません。
3)上記リンク先にありますように、ncWaitForState関数は、Read MultipleとWrite Multipleをサポートしていないと認識しております。
上記内容をご確認頂き、ご不明な点がございましたらご返信くださいますようお願いいたします。
よろしくお願い致します。

Using Frame API for C, Need to change Data size for a TX Object

I need to Transmit different messages to the same ArbitrationID address. The Transmited messages have variable lengths. Can I call ncConfig on an object to change the NC_ATTR_CAN_DATA_LENGTH even after the call to ncOpenObject. Or do I have to Close the object and reopen it after the call to ncConfig?
Thanks!

Hello Genesis,
your second assumption is right. You do have to close, reconfigure and reopen the object in order to change the data length.
As long as you're using the CAN Object in the 'Transmit Data by Call' mode only, you might want to consider using the Network Interface for transmitting. When you use the Network Interface, you can change the ArbitrationID for each write call.
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Why do I get an error of B2010002, when I open an NI-CAN object?

I am using the configuration of the property page to setup the PCI-CAN card. I am using Extended Arbitration Number of 0xFEF100. My code is in VB 5.0. The code works with a number less than 0xFFFFF. The B201002 is an Implentation-specific error in NI-CAN driver. As soon as I try to open the CAN object this error is generated.

Hello-
A Status code of hex ....0002 tells us that it's a driver error (NC_ERR_DRIVER).
Here's some solutions:
-Be sure the card passes NI-CAN Diagnostics
-Map Port1 to CAN0 and Port2 (if exists) to CAN1. This is done in the NI-CAN configuration utility in Win NT/2000 or through Device Manager in Win 9X/ME.
-We have a limit of 50 CAN objects and 150 frames in the queues of these objects. It may be necessary to readjust these settings.
Kim L.
Applications Engineer
National Instruments

CAN Object Transmits Waveform on RTSI

I have a question to the above mentioned VI. The ncWriteObj.vi is placed in a For loop here. Does this mean that the For loop is executed once every time an RTSI event occurs???

Hi SVJ,
the For loop in the mentioned example is executed 8 times before the CAN object is started. Since there is a 8 element queue configured in the ncConfigCANObjRTSI.vi these 8 CAN frames are transmitted after starting the communication using ncAction. After 8 RTSI pulses when the queue is empty the object repeats the last frame until new frames are written into the queue using ncWriteObj (within the while loop).
If you encounter queue overflow problems please refer to the following knowledgebase:
http://digital.ni.com/public.nsf/allkb/862567530005F0A186256A3F005FAB83?OpenDocument
or the "NI CAN Hard- and Software manual" p. 10-150 ncWriteObj.
Message Edited by AndreasS on 11-10-2008 08:57 AM
Andreas S
Systems Engineer

NI-CAN Frame API: Variable Periodic CAN Object

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