Callback function pointer in Matlab

I am trying to call a function from Matlab NI daqmx toolbox:

function [status, callbackData] = DAQmxRegisterEveryNSamplesEvent(uint64 task, int32 everyNsamplesEventType, uint32 nSamples, uint32 options, DAQmxEveryNSamplesEventCallbackPtr callbackFunction, void* callbackData)

This function requires a callbackFunction pointer as input but I have no idea how to create that in Matlab and matlab function handle doesn't work for it. Could anyone help me with this issue?

Answer 1

[Image Analyst]

You put an @ symbol in front of the argument when you call it. For example calling it might look like

[status, callbackData] = DAQmxRegisterEveryNSamplesEvent(task, everyNsamplesEventType,...
 nSamples, options, DAQmxEveryNSamplesEventCallbackPtr, @MyCallbackFunction, callbackData)

where you've assigned values for the other arguments. Then you'd define that MyCallbackFunction() function somewhere, like

function results = MyCallbackFunction()
% code...
% The function needs to know what will be given to it when DAQmxRegisterEveryNSamplesEvent() gives stuff to it
% and what kind of data DAQmxRegisterEveryNSamplesEvent() expects to get back after MyCallbackFunction has been executed.

[Qi Pian]

funtion handle like @function doesn't work.

I got this error when replacing function pointer with function handle:

" Error using DAQmxRegisterEveryNSamplesEvent

Expected input number 5, callbackFunction, to be one of these types:

int32

Instead its type was function_handle.

Error in DAQmxRegisterEveryNSamplesEvent (line 9)

validateattributes(callbackFunction, {'int32'}, {'scalar'},

'DAQmxRegisterEveryNSamplesEvent', 'callbackFunction', 5);"

[Image Analyst]

Then I don't know. Try calling NI tomorrow and asking for sample code.

[Qi Pian]

Thanks a lot!