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. |