No signal being seen on CANbus from NI Card

[NPrice]

I have a PCI CAN/DS Series 1 can PCI card installed in my computer and connected to a CAN network with 2 micros. Both micros are able to transmit and receive messages to each other on the CAN bus. When I try to send messages from the PCI card on the CAN bus, NIMax software says it is sending messages on the channel but nothing appears on the physical layer (2-wire). (I have an oscilloscope monitoring the bus and when the micros transmit you can see the data frames being transmitted).

Also the PCI card refuses to see any messages being sent on the CAN bus by the micros. The baud rates are the same and there is a 120ohm resistor terminating the CANH and CANL lines.

Any ideas?

Thanks,
Neil

[DirkW]

The PCI DS Card uses a Low Speed Transceiver on Port 2.
Therefore you can only use Speeds below 125 KBaud.
Try to remove the resistor from the cable you are use, because the low speed transceiver uses a special resistor on the board. Last but not least you need power on the bus to work with the low speed port. Be sure that the high speed port is internaly powered, so we will have power on the bus . The low speed bus is unable to use the internal power. So alternatively you can power the bus using the V+ and V- pins.
Hope that helps.

[ScottieB]

Dirk's answer is right on. I would be curious as to what port you are using, and whether you expect this to be a high speed or a low speed CAN network. Let us know and we can help you out. Was this card working before, or is it a new card? If the port you are using is bus powered and you do not have power on the bus, the transceivers will not transmit anything and you will see the behavior that you are seeing with MAX.

Hope this helps.

Scott B.
Applications Engineering
National Instruments

[NPrice]

Okay I think I've got it working now thanks. I didn't have power on the bus (not realising it was necessary for just one port). I am successfully transmitting data frames... just have to sync with the micros now! Incidentally - is there any technical documentation available for the PCI card I'm using? I couldn't find any online and didn't receive any with it.

Thanks,
Neil

[ScottieB]

All technical documentation should be found in the Hardware / Software manual. It includes a description of the API as well as specs on the card. Here is a link:

http://digital.ni.com/manuals.nsf/websearch/E1B63B10FEBBBBCB86256EA00008031D?OpenDocument&node=132100_US

Scott B.
Applications Engineer
National Instruments