Can Dnet PCI card work at 16Mhz CAN bit timing?

[Lupita]

I am working with Labview 7.1 and Ni Dnet 1.4.1. I had a Dnet I/O Block that used to work at 11.0592 and now that it changed to 16 Mhz it is not able to go establish a POLL connection. The Dnet manufacturer claims the only thing that changed was the CAN bit timing. I am working with Labview 7.1. It seems to be a timing issue but adding pauses and wait VIs doesnt seem to solve the problem. Thank you.

[Krista H]

Hi Lupita,

It seems to me that the change in your device has caused this issue. When you say it no longer works what do you mean? Are you getting any errors?  If so what are they and what are thier descriptions? A little more information on how it's not working and how it is supposed to work would be helpfull.

[Lupita]

Hi Krista,

When running the SingleDevice.vi on the Ni-dnet example library. The old device runs just fine. The new one (16MHz) has an error:

0xBFF62001 (Timeout error) when attempting to write using  Write Devicenet IO.vi. Do you know if in fact the NI PCI card can work at that speed if the baud rate did not change (125k)? Thanks

[Paul M.]

Lupita,

You mention that the bit timing DID change, but later on say that the baud rate did NOT change. Are you sure the device is still operating at 125kBit? Chances are that we are operating at a different baud rate now. As long as your device conforms to the standard high-speed CAN physical layer, then the NI DeviceNet card will work with it. 

Bit timing parameters are not set in LabVIEW, but in Measurement and Automation Explorer.  You can configure the interface hardware baud rate or bit timings there. If you know the specific bit timing registers you want to use, you can also specfiy those there.  Hope this helps!

[frankwu]

Hi Lupita,

If a device runs at 125kbps, then NI-DNET can communicate with it (no matter what oscillator is in the device).
If a device uses a different oscillator, then the manufacturer should change its firmware to tune the CAN bit timing for the baud rate.

The problem may be that the new device doesn't run at 125k baud rate after the oscillator is changed.
You can check the problem by the following way. If it is true, please ask your device manufacturer to fix the CAN bit timing.
1. launch MAX
2. select you CAN card > Protocol > change to "CAN'
3. select you CAN port (CAN0) > Bus Monitor
4. connect your old device and make sure that 2 messages appears in the bus monitor
5. connect your new device. If no message appears, then the device doesn't run at 125kbps.

Regards,
Frank

[Lupita]

Hi,

I ran CAN and got the following CAN information (new device first). Is it possible that the NI-dnet card (CAN controller Intel 82527 and Philips 82c250 transceiver) is just not able to handle the new CAN transmission rate (1.45 Hz)?

I was able to establish communication with a SST card (SJA CAN controller and TJA transceiver)

Thank you.

[frankwu]

Do you use the same CAN card for bus monitor and DNET?
If Yes, then the card can capture the CAN packet.

Maybe you can connect both old and new device with the CAN card and try again.

[DirkW]

Hi,

Could you run the simple who? example to see you can find the device? If not please run the NI-Spy together with the simple who example. The NI SPY comes with the driver and you can run it from START>>PROGRAMS>>National Instruments. It logs all API calls and we could check whether or not the driver receives messages but the DNET API can not use them.

DirkW