Hardware timestamped frequency measurement

[derekpleb]

Hello there,

I'm trying to get stream of counter / timer measurements with proper hardware timestamps corresponding to the start of the measurement using DAQMX.  I don't want a software timestamp like that provided in DAQ assistant.  I'm thinking I may need to initiate or arm some kind of internal trigger event.  The card would take the measurement as determined by the external signal and then send back the result with the exact time the counter was triggered into action.  I can't seem to find any counter timer code that does this.  I'm using a USB6221 to look at deceleration in free running mechanical assemblies.  I'd like to take readings at up 500Hz.

Anyone done this before?

Chris 

[derekpleb]

I got some support suggesting the use of two counters to achieve a time correlated counter/timer event.  This is pretty ugly but I will use it if I have to.  

It may be easier to do this by signal processing an analogue input with a suitably fast sample rate.  Ok there's no way I can detect edges as well as the 80Mhz counter clock but it may work if I average over an adequate number of cycles.  Has anyone else got a better idea than the official suggestion here?

 http://zone.ni.com/devzone/cda/epd/p/id/6169