NI-DAQmx Counter Frequency Measurement

Question

I need to measure the number of pulses obtained within a time period (3 secs).
So if i use channel 0 to generate a gate pulse for channel 1 how can i do other other things while waiting for my 3 seconds to be up ?
Has anyone got any VB6 code to do it. At the moment i have a task in Max to generate the pulse train with two leading edges every 3 secs.
I use this output to gate the second counter channel. I then have a task created in VB to count edges. Then i would like
DAQmxReadCounterU32 to NOT hold up execution while reading two samples.
something like......
while waiting for two samples
loop

Answer 1

Assuming you're doing buiffered event counting, you can monitor the status of the buffer without blocking by using the Read Properties.  I don't know the exact VB syntax, put the equivalent C funtion you need is:
DAQmxGetReadAvailSampPerChan(TaskHandle taskHandle, uInt32 *data)
You can use this function to poll within a loop and then call read only after a certain number of samples are available.  You can also continue to use the Read function but pass in a timeout of 0 or pass -1 for the number of samples to read.  Passing -1 will tell the driver to read all samples that are currently available and then return.  Depending on the method, you'll either have to handle timeout errors or check the actual number of samples read to see if you actually read anything, but neither method will block until samples become available.  You could also register a callback funtion for the Every N Samples Acquired Into Buffer Event and perform your read in that callback.  I hope this helps.