"timestamp using fpga module on pxi-7831R"

[graduate student 44]

"i'm having a pxi-7831r listening to a digital signal initiated by the master card on the same chasis. each time it is triggered, it takes a timestamp relative to a 64bit clock counter (i used two U32 for the 64bit counter). the triggering frequency from master card is on the order of 50khz and i'll need to store all timestamps on the host computer eventually.

i'm new to fpga programming. what will be a good strategy for this problem? i'm thinking of making the fpga vi output the current timestamp to the host computer each time it is triggered, but that means it has to output two U32 integers 50000 times/s to the host vi. or should i build an array and store chunks of timestamps on the pxi and let the host vi read them o
nce a while? or anything else?"

[Westscape]

graduate student wrote:

> "i'm having a pxi-7831r listening to a digital signal initiated by the
> master card on the same chasis. each time it is triggered, it takes a
> timestamp relative to a 64bit clock counter (i used two U32 for the
> 64bit counter). the triggering frequency from master card is on the
> order of 50khz and i'll need to store all timestamps on the host
> computer eventually.
>
> i'm new to fpga programming. what will be a good strategy for this
> problem? i'm thinking of making the fpga vi output the current
> timestamp to the host computer each time it is triggered, but that
> means it has to output two U32 integers 50000 times/s to the host vi.
> or should i build an array and store chunks of timestamps on the pxi
> and let the host vi
read them once a while? or anything else?"

I would expect you will need to do some buffering. I have not tried your
specific application but have done some involving transfer of single
points synchronised by interrupts and it was difficult to get much above
the 10 to 12 KHz region.
There is an example of doing some buffered DAQ somewhere on ni.com
although I haven't tried it myself yet. I believe this made use of the
onboard RAM on the 7831R. It might be a good starting point.

[Westscape]

Just found the example here:
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=C065DB008AE1363DE034080020E74861&p_node=200449&p_source=external

typical long url!

Any trouble just search for 'fpga buffered' on ni.com it is the first
article.

[graduate student 44]

that makes sense. i'll give it a shot. THanks!