Continous Acq with 6220 and Reference Trigger??

[StephenKy]

Hi,

I'm using the NI-6220 DAQ card on Windows XP and the DAQmx C drivers.

My application needs to do the following:
Read samples continously at full speed (250,000 samps/sec)
Use an external digital singal runing at 1PPS (from a GPS device) to precisely time stamp the beginning of a second.
When the 1PPS comes in, transfer the last 1 sec of data (250,000 samples) to memory and keep going.
This process runs continously and I need to do processing while new samples are being taken.

The prolem I am running into is that if I use the "DAQmx_Val_FiniteSamps" with the "DAQmxCfgSampClkTiming" function, the line of code blocks until the DAQ reads all the data.  Therefore, there is never any time to process the data (i.e you have to stop reading.... process data... start reading... stop.  process data. start... etc).  This is unacceptable in that I need to continously sample.

If is use the "DAQmx_Val_ContSamps" setting with the "DAQmxCfgSampClkTiming" function, I get a error that say you can't use "DAQmx_Val_ContSamps" with a reference trigger.

Can anyone help or tell me who to cal at NI who can?

Thanks
Stephen

[lrallen]

Stephen,

The only product we have that can do this kind of timestamping is the 6608. See the link below and let me know if this is not what you need to do. 

6608: http://zone.ni.com/devzone/conceptd.nsf/webmain/2fad3b4e67ba766186256b9c00679f75

Regards,

L. Allen

[StephenKy]

Thanks for the reply.

Actually we have already designed a PCB which uses a GPS module and outputs a TTL level 1PPS from the GPS to PFI0 of the NI-6220 DAQ Card (the PCB also does other analog processing and sends signals to AI1-AI3).

So, we are locked into the 6220 Card.

Ideally, we need the 6220 to run in continous mode and accept reference triggers.

Any ideas?

Thanks
Stephen

[Justin_M]

Hi Stephen,

Take a look at the following example:

NI-DAQmx: Continuous Analog Input with Both Start and Reference (Stop) Triggers - LabVIEW - CVI - AN...

It looks like it's close to what you want to do.  Could be a good starting point...

Thanks,

Justin M
National Instruments