Why are the CAN drivers so sloooooow?

[ct 126]

In my VC++ application using V1.4 of the drivers, I am communication with a device while I watch the bus with a scope. I have two frames to send to a device, but due to my protocol, I must wait for a response to the first before sending the second. I am using the ncCallback to get and process the response and send the second frame.

When I look at the scope, it takes about 10ms for the callback to run and generate the next frame. (Time measured from device response to next outgoing frame.) My effective communication rate is this manner is about 9600 Baud. 😞

Any ideas on how to speed this up?

[Randy Solomonson]

It may help to refer to the "Communication Types" section of the NI-CAN Programmer's Reference Manual (available at ni.com/manuals). Be sure that the transmit data periodically communication type is not being used.

It sounds like either the Transmit Value By Response or even Transmit Data By Call is more practical in this situation.

If this isn't the problem please drop us a support email.

Randy Solomonson
Application Engineer
National Instruments
support@ni.com