DAQmxRegisterSignalEvent

int32 DAQmxRegisterSignalEvent (TaskHandle taskHandle, int32 signalID, uInt32 options, DAQmxSignalEventCallbackPtr callbackFunction, void *callbackData);

Purpose

Registers a callback function to receive an event when the specified hardware event occurs.
When you stop a task explicitly any pending events are discarded. For example, if you call DAQmxStopTask then you do not receive any pending events.

Parameters

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
signalID	int32	The signal for which you want to receive results. Value Description DAQmx_Val_SampleClock Sample clock DAQmx_Val_SampleCompleteEvent Sample complete event DAQmx_Val_ChangeDetectionEvent Change detection event DAQmx_Val_CounterOutputEvent Counter output event
options	uInt32	Use this parameter to set certain options. You can combine flags with the bitwise-OR operator ('|') to set multiple options. Pass a value of zero if no options need to be set. Value Description 0 The callback function is called in a DAQmx thread. This is the default value. DAQmx_Val_SynchronousEventCallbacks The callback function is called in the thread which registered the event. In order for the callback to occur, you must be processing messages. Note If you are receiving synchronous events faster than you are processing them, then the user interface of your application might become unresponsive.
callbackFunction	DAQmxSignalEventCallbackPtr	The function that you want DAQmx to call when the event occurs. The function you pass in this parameter must have the following prototype: int32 CVICALLBACK Callback (TaskHandle taskHandle, int32 signalID, void *callbackData); Upon entry to the callback, the taskHandle parameter contains the handle to the task on which the event occurred. The signalID parameter contains the value you passed in the signalID parameter of this function. The callbackData parameter contains the value you passed in the callbackData parameter of this function.
callbackData	void *	A value that you want DAQmx to pass to the callback function as the function data parameter. Do not pass the address of a local variable or any other variable that might not be valid when the function is executed.

Return Value

Name	Type	Description
status	int32	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. A negative value indicates an error.