How to reduce delay caused by coding?

Question

Hi,
I am fairly new to C++ programming and using DAQ boards. I've been browsing this board for awhile and let me first thank everyone who has contributed - most threads were very helpful.
However this problem I have right now didn't come up in any searches so hopefully someone could help me out.
I am using the NI-6115 PCI DAQ board and I am trying to write a simple C program that continuously counts the number of input pulses to a counter within a time period.  The program also has to continuously output the result onto the screen.
 So basically this is what my code looks like:
 while( 1 ) {
        DAQmxErrChk (DAQmxReadCounterScalarU32(taskHandle,10.0,&data,NULL));
        count = data - data1;
        if ((long)count < 0)
            (uInt32)count = data + 16777216 - data1;
        data1 = data;
        printf("\rCount: %d.  Press Ctrl+C to interrupt.            ",count);
        fflush(stdout);
        DAQmxErrChk (DAQmxWaitForNextSampleClock(taskHandleCtr,10.0,0));
 The sample clock uses another counter's output pulse train as the source.
The problem is, the desired execution time of each iteration is around 40 - 50 microseconds.  With the above coding, I could only achieve 800 microseconds per iteration.  If  I set the sample clock any faster, an error will occur telling me that two sample clock pulses have occured before the "DAQmxWaitForNextSampleClock" instruction is reached.
Would it be the computer that I am running the program on?  The speed of the DAQ board?  Or just poor programming technique on my part?
Thanks in advance
Howard
Message Edited by HT156 on 05-14-2009 06:17 PM
Solved!
Go to Solution.

Answer 1

Thanks for you last reply David.
Since switching to a new OS is not an option for me, I have decided to reconsider my program logic in order to achieve an even faster time. 
I have decided to store the read counter values first then do the calculations later.  Also, I have omitted the part of continuously printing the results onto the screen.  Here's what remains of my code, which is incomplete.
while( 1 ) {
        DAQmxErrChk (DAQmxReadCounterScalarU32(taskHandle,10.0,&data,NULL));
        DAQmxErrChk (DAQmxWaitForNextSampleClock(taskHandleCtr,10.0,0));
However even with those two lines of codes I am only able to get down to 350 microseconds per iteration before WaitForNextSampleClock returns an error.  I was wondering if there is a faster read function to read the counter value than  DAQmxReadCounterScalarU32?  And is there a way to bypass the CPU and store the counter values direct onto the DAQboard?