What is the buffer size the NI CAN-8473 allocates?

[vivekde]

Hi,

Need to know what is the buffer size of NI-USB 8473 device and does it follow queue structure. We are having requirement to fetch all the queue data that are in the buffer. What will happen to the packet in case I've missed out to read it and other packet has already come. In this case which packet will be read by us if we wish to read the buffer? Will the old one will be overwritten by the new?

Please help me in clearing my doubts....

Regards,

Vivek

[DirkW]

Hi,

The NI-USB devices have a totaly different approach for buffering write and read operations, then our Plug In boards. because it is USB , the driver buffers all the frames for Write operations in Host memory. For Read operations there is a small memory at the device but the driver transfers as fast as possible and buffers the frames in Host memory as well.

Thus you do not need to configure queues with the config function at all. I have not seen a overflow error so far, even with Full Speed USB.

Hope that helps.

DirkW

[Don_White]

This is odd because if I wait too long to call ncWaitForState then ncReadMult I start getting messed up data.

Looks like a ping-pong buffer gone astray.

(I have a Sleep() with a user defineable number of milliseconds in the loop that calls ncWaitForState/ncReadMult.)

Don White

Concord, CA.