Laptop/Desktop configuration for High Speed CAN USB NI USB-8473

[Tejas_purandare]

Hi, We are evaluating NI USB 8473 for one of the upcoming project. My requirement is as follows. 1. The NI USB 8473 will be connected to a Laptop which will emulate more than one CAN Nodes and communicate with Other System. The system on other side would be built on a real time platform. 2. I will send different parameters at different update intervals over the CAN using CAN Open. 3. I need my application to support sustained bus load of 100% at 1 Mb/s over CAN (CAN Open) and test and prove that it works as specified. I would like to know the following: 1. Whether (NI USB 8473) would be a suitable selection for the requirement that I have mentioned above. 2. What would be the suitable Laptop configuration for me to get speed up to 1 Mb/s. (In terms of CPU, USB port, RAM, Operating System, Bus Speed etc...Lets assume we use NI Labview built application on the Laptop). 3. The PC / Laptop CPU Loading for this to run. - TCP

[labviewman]

I use the USB-8473 to simulate (and log all CAN bus data) as many 15 ECUs (J1939 at 250 Kbps), but regarding CPU usage, it depends on how you write your code.  A modem low-grade dual-core computer can easily handle a 100% loaded 1Mbps CAN bus, but it depends on your code...polling in a tight loop w/o any delay will waste CPU time, and what you do with the data (i.e. screen updates) will affect CPU usage.

I have experienced problems with all NI high-speed non-XNET CAN devices in regards to reliably sending out data for an extended period of time.  With my simulations (and a simplified version I sent NI), the CAN messages would run w/o problems for only for a few hours, then stop sending messages for no reason at all (no error codes).  I worked around the bug by detecting when the transmit buffer would fill-up, at which point I would reset the card.  NI was able to duplicate this but as far as I know, has not fixed the issue.

If you must use NI, it would be best to use an XNET card unless you can work around this NI-CAN problem.

BTW, NI CAN devices are only supported under Windows, and if CAN bus-off happens, you have to recover from the error yourself (other devices, even $5 PIC micros do this automatically).

I hope this helps,

Todd

[Tejas_purandare]

Thanks Todd for sharing your experience.

I need to have my interface that suits Laptops and Desktops.

May be XNET will have to sit on the PCI / PXI.

I am also asking NI if they have closed such open issues in their subsequent releases.

cheers,

TCP

[anekhoda]

If you open CAN port and handle references via loop Registers you shouldn't have any problem with USB-8473.

I run my code for weeks without any problems. "ref in -> ref. out"

[GPIB_Guru]

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@labviewman wrote:
BTW, NI CAN devices are only supported under Windows, and if CAN bus-off happens, you have to recover from the error yourself (other devices, even $5 PIC micros do this automatically).

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Note, it is a violation of the spec to have the interface automatically recover from CAN bus-off.

Per ISO 11898,

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section 4.14 "bus off"

A nodes is in the state "bus off" when it is switched off from the bus due to a request of fault confinement entity. In the "bus off" state, a node can neither send nor receive any frams. A node can leave the "bus off" state only upon a user request.

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