Meaning of return value from DAQmxEveryNSamplesEventCallbackPtr

[CVilla]

When using DAQmxRegisterEveryNSamplesEvent, the function pointer type DAQmxEveryNSamplesEventCallbackPtr is declared as returning an int32.  Does NI-DAQmx do anything with this value?  All the examples I've seen only return 0.

Also I've tried to figure out where best to put the DAQmx C api questions.  It seems there are more questions in this forum than Measurement Studio C++.

[S_Hong]

Hi CVilla,

The return value from DAQmxRegisterEveryNSamplesEvent is the error code returned by the function in the event of an error or warning; a value of 0 indicates success, a positive value indicates a warning, and a negative value indicates an error. The NI-DAQmx C Reference Help is a great resource to use when programming DAQmx in C. This can be found in your Start Menu under National Instruments » NI-DAQ.

As for posting DAQmx C API questions, this is the proper forum to post such questions as programming DAQmx still falls under the umbrella of Multifunction DAQ.

I hope this helps,

[CVilla]

I guess my question was not clear.  I understand the return values when my code calls DAQmx functions.  The return value constants are in the header file.

What I do not understand, which is not described in the C api help file, is what does DAQmx do with the return code from my event function?

If I write a function and register it with DAQmxRegisterEveryNSamplesEvent like this:

DAQmxRegisterEveryNSamplesEvent(..., MyFunction, ...)

int32 MyFunction(...)
{
// do stuff here
if (ok)
    return 0;
else
    return -1;
}

When the DAQmx thread calls my function and I return a value, what does DAQmx do with the return value?  If I return -1 instead of 0 does DAQmx behave differently?  If so, how?

[ldp]

The return value from your C API callbacks is ignored by the API as of now.

Hope this helps.
LDP

[CVilla]

OK - thanks!