NI USB 8472 - CAN communication

[ialonso]

Hello,

First of all, I will describe what I want to do. I have two boards communicated by CAN, both of them have a terminator. Now I would like to develop an automatic test. For that, I am trying to simulate one of them with a NI USB-8472 module. I also have a CAN CABLE WITH NO TERMINATION (193128B-01) and a CAN CABLE WITH A SINGLE TERMINATION (192017A-02). 

The first question would be, how do I have to connect my NI module with the board?

I tried to receive CAN messages from my board using ncReadNetMult.vi but I cannot see the messages, however I do not have any errors.

Also, if someone could tell me a good example to begin with, I would appreciate it so much.

Thanks in advance for your help.

[ialonso]

Hi again,

I was doing some tests with MAX and different wires (configurations). If I connect directly from DB9 connector to my board and I remove the terminator in my board I receive the CAN messages prefectly. If I put the resistor in my board, when I try to start the communication I get the 3FF6200C which indicates that there is a problem in the bus. In order to remove the error I connect the CAN CABLE NO TERMINATION, in that case there is no error but the communication does not work.

It seems like my board has a high speed CAN device. Which causes the communication problems I am having. Is it possible? If this is true, how can I solve this situation?

Thanks in advance.

[DirkW]

The 8472 does not bring any termination resistors and powers everything internally so you should be good on that side. However Termination is tricky and sometimes just one 120 ohms resistor is enough especially when you deal with short cables under 3 meters.

Besides that make sure your resistor is between CANH and CAN L. If you want to make it easier to debug you could use the breakout box  Ni sells and some non terminated cables. 

http://sine.ni.com/nips/cds/view/p/lang/en/nid/211322

-DirkW-

[ialonso · Accepted solution]

Hi,

Finally I resolved the problem. I write the solution in case it will help anyone.

NI USB-8472 is a low speed device and my board's CAN module is high speed, so they can't communicate if the high speed device has the terminator. In my case I can resolve the problem with a NI USB-8473 or how I do for the moment with an adapter like this: http://www.peak-system.com/PCAN-TJA1054.219.0.html?&L=1

I hope this message will be useful for anyone.

However, thank you for your replies and your time.

[Minions]

If either of the devices were software configurable, then this would not have been an issue.  The software allows the baud rate to be configured on-the-fly within the A2L file called out using the OPEN vi.