• DAQmxAddGlobalChansToTask
• DAQmxClearTask
• DAQmxConfigureLogging
• DAQmxCreateTask
• DAQmxIsTaskDone
• DAQmxStartTask
• DAQmxStartNewFile
• DAQmxStopTask
• DAQmxWaitUntilTaskDone
• Events
  • DAQmxRegisterDoneEvent
  • DAQmxRegisterEveryNSamplesEvent
  • DAQmxRegisterSignalEvent
• Advanced
  • DAQmxGetNthTaskChannel
  • DAQmxGetNthTaskDevice
  • DAQmxTaskControl

int32 DAQmxAddGlobalChansToTask (TaskHandle taskHandle, const char channelNames[]);

Adds global virtual channels from MAX to the given task.

Input
Name	Type	Description
taskHandle	TaskHandle	The task to which to add the channels from MAX.
channelNames	const char []	The channels to add to the task. You can specify a list or range of channels. These channels must be valid channels available from MAX. If you pass an invalid channel, NI-DAQmx returns an error. This value is ignored if it is empty.

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.

int32 DAQmxClearTask (TaskHandle taskHandle);

Clears the task. Before clearing, this function aborts the task, if necessary, and releases any resources reserved by the task. You cannot use a task once you clear the task without recreating or reloading the task.

If you use the DAQmxCreateTask function or any of the NI-DAQmx Create Channel functions within a loop, use this function within the loop after you finish with the task to avoid allocating unnecessary memory.

Input
Name	Type	Description
taskHandle	TaskHandle	The task to clear.

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.

int32 DAQmxConfigureLogging (TaskHandle taskHandle, const char filePath[], int32 loggingMode, const char groupName[], int32 operation);

Configures TDMS file logging for the task.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
filePath	const char []	The path to the TDMS file to which you want to log data.
loggingMode	int32	Specifies whether to enable logging and whether to allow reading data while logging. Log mode allows for the best performance. However, you cannot read data while logging if you specify this mode. If you want to read data while logging, specify Log and Read mode.

Value		Description
DAQmx_Val_Off		Disable logging for the task.
DAQmx_Val_Log		Enable logging for the task. You cannot read data using DAQmx Read when using this mode. If you require access to the data, read from the TDMS file.
DAQmx_Val_LogAndRead		Enable both logging and reading data for the task. You must use DAQmx Read to read samples for NI-DAQmx to stream them to disk.

groupName	const char []	The name of the group to create within the TDMS file for data from this task. If you append data to an existing file and the specified group already exists, NI-DAQmx appends a number symbol and a number to the group name, incrementing that number until finding a group name that does not exist. For example, if you specify a group name of Voltage Task, and that group already exists, NI-DAQmx assigns the group name Voltage Task #1, then Voltage Task #2. If you do not specify a group name, NI-DAQmx uses the name of the task. For digital input tasks, NI-DAQmx creates a group for each virtual channel in the task. For each created group, NI-DAQmx appends a hyphen and the virtual channel name to the group name.
operation	int32	Specifies how to open the TDMS file.

Value		Description
DAQmx_Val_Open		Open an existing TDMS file, and append data to that file. If the file does not exist, NI-DAQmx returns an error.
DAQmx_Val_OpenOrCreate		Open an existing TDMS file, and append data to that file. If the file does not exist, NI-DAQmx creates a new TDMS file.
DAQmx_Val_CreateOrReplace		Create a new TDMS file, or replace an existing TDMS file.
DAQmx_Val_Create		Create a new TDMS file. If the file already exists, NI-DAQmx returns an error.

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.

int32 DAQmxCreateTask (const char taskName[], TaskHandle *taskHandle);

Creates a task . If you use this function to create a task, you must use DAQmxClearTask to destroy it.

If you use this function within a loop, NI-DAQmx creates a new task in each iteration of the loop. Use the DAQmxClearTask function within the loop after you finish with the task to avoid allocating unnecessary memory.

Input
Name	Type	Description
taskName	const char []	Name assigned to the task.

	Note This name may be changed internally. If you are using the C API, call DAQmxGetTaskName to verify whether the name was changed during creation. If you are using the CVI API, call DAQmxGetTaskAttribute with attribute ID DAQmx_Task_Name to verify the name change.

Output
Name	Type	Description
taskHandle	TaskHandle *	A reference to the task created in this function.

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.

int32 DAQmxIsTaskDone (TaskHandle taskHandle, bool32 *isTaskDone);

Queries the status of the task and indicates if it completed execution. Use this function to ensure that the specified operation is complete before you stop the task.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
Output
Name	Type	Description
isTaskDone	bool32 *	Indicates whether the measurement or generation completed.

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.

int32 DAQmxStartTask (TaskHandle taskHandle);

Transitions the task from the committed state to the running state, which begins measurement or generation. Using this function is required for some applications and optional for others.

If you do not use this function, a measurement task starts automatically when a read operation begins. The autoStart parameter of the NI-DAQmx Write functions determines if a generation task starts automatically when you use an NI-DAQmx Write function.

If you do not call DAQmxStartTask and DAQmxStopTask when you call NI-DAQmx Read functions or NI-DAQmx Write functions multiple times, such as in a loop, the task starts and stops repeatedly. Starting and stopping a task repeatedly reduces the performance of the application.

Input
Name	Type	Description
taskHandle	TaskHandle	The task to start.

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.

DAQmxStartNewFile(TaskHandle taskHandle, const char filePath[]);

Starts a new TDMS file the next time data is written to disk.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
filePath	const char []	The path to the TDMS file to which you want to log data.

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.

int32 DAQmxStopTask (TaskHandle taskHandle);

Stops the task and returns it to the state it was in before you called DAQmxStartTask or called an NI-DAQmx Write function with autoStart set to TRUE.

If you do not call DAQmxStartTask and DAQmxStopTask when you call NI-DAQmx Read functions or NI-DAQmx Write functions multiple times, such as in a loop, the task starts and stops repeatedly. Starting and stopping a task repeatedly reduces the performance of the application.

Input
Name	Type	Description
taskHandle	TaskHandle	The task to stop.

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.

int32 DAQmxWaitUntilTaskDone (TaskHandle taskHandle, float64 timeToWait);

Waits for the measurement or generation to complete. Use this function to ensure that the specified operation is complete before you stop the task.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
timeToWait	float64	The maximum amount of time, in seconds, to wait for the measurement or generation to complete. The function returns an error if the time elapses before the measurement or generation is complete. A value of -1 (DAQmx_Val_WaitInfinitely) means to wait indefinitely. If you set timeToWait to 0, the function checks once and returns an error if the measurement or generation is not done.

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.

Note: see Using Callback Functions for an example of how to use this through gRPC.

int32 DAQmxRegisterDoneEvent (TaskHandle taskHandle, uInt32 options, DAQmxDoneEventCallbackPtr callbackFunction, void *callbackData);

Registers a callback function to receive an event when a task stops due to an error or when a finite acquisition task or finite generation task completes execution. A Done event does not occur when a task is stopped explicitly, such as by calling DAQmxStopTask.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
options	uInt32	Use this parameter to set certain options. You can combine flags with the bitwise-OR operator ('

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. Windows This option is supported only on Windows.

	Note If you are receiving synchronous events faster than you are processing them, then the user interface of your application might become unresponsive.

callbackFunction	DAQmxDoneEventCallbackPtr	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 status, void *callbackData); Upon entry to the callback, the taskHandle parameter contains the handle to the task on which the event occurred. The status parameter contains the status of the task when the event occurred. If the status value is negative, it indicates an error. If the status value is zero, it indicates no error. If the status value is positive, it indicates a warning. The callbackData parameter contains the value you passed in the callbackData parameter of this function. Passing NULL for this parameter unregisters the event callback function.
callbackData	void *	A value that you want DAQmx to pass to the callback function as the function data parameter. Callback functions may be called even after a task is cleared. Do not pass the address of a local variable, a variable associated with a cleared task, or any other variable that might not be valid when the function is executed.

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.

Note: see Using Callback Functions for an example of how to use this through gRPC.

int32 DAQmxRegisterEveryNSamplesEvent (TaskHandle taskHandle, int32 everyNsamplesEventType, uInt32 nSamples, uInt32 options, DAQmxEveryNSamplesEventCallbackPtr callbackFunction, void *callbackData);

Registers a callback function to receive an event when the specified number of samples is written from the device to the buffer or from the buffer to the device. This function only works with devices that support buffered tasks. 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.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
everyNsamplesEventType	int32	The type of event you want to receive.

Value		Description
DAQmx_Val_Acquired_Into_Buffer		This event type is only supported for input tasks. Events occur when the specified number of samples are acquired into the buffer from the device.
DAQmx_Val_Transferred_From_Buffer		This event type is only supported for output tasks. Events occur when the specified number of samples are transferred from the buffer to the device.

nSamples	uInt32	The number of samples after which each event should occur.
options	uInt32	Use this parameter to set certain options. You can combine flags with the bitwise-OR operator ('

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. Windows This option is supported only on Windows.

	Note If you are receiving synchronous events faster than you are processing them, then the user interface of your application might become unresponsive.

callbackFunction	DAQmxEveryNSamplesEventCallbackPtr	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 everyNsamplesEventType, uInt32 nSamples, void *callbackData); Upon entry to the callback, the taskHandle parameter contains the handle to the task on which the event occurred. The everyNSamplesEventType parameter contains the value you passed in the everyNSamplesEventType parameter of this function. The nSamples parameter contains the value you passed in the nSamples parameter of this function. The callbackData parameter contains the value you passed in the callbackData parameter of this function. Passing NULL for this parameter unregisters the event callback function.
callbackData	void *	A value that you want DAQmx to pass to the callback function as the function data parameter. Callback functions may be called even after a task is cleared. Do not pass the address of a local variable, a variable associated with a cleared task, or any other variable that might not be valid when the function is executed.

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.

Note: see Using Callback Functions for an example of how to use this through gRPC.

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

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.

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 ('

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. Windows This option is supported only on Windows.

	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. Passing NULL for this parameter unregisters the event callback function.
callbackData	void *	A value that you want DAQmx to pass to the callback function as the function data parameter. Callback functions may be called even after a task is cleared. Do not pass the address of a local variable, a variable associated with a cleared task, or any other variable that might not be valid when the function is executed.

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.

int32 DAQmxGetNthTaskChannel (TaskHandle taskHandle, uInt32 index, char buffer[], int32 bufferSize);

Returns the Nth channel. This function takes the taskHandle, index, and bufferSize you specify and returns the Nth channel.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
index	uInt32	The Nth channel to return. The index starts at 1.
bufferSize	int32	The size, in bytes, of buffer. If you pass 0, this function returns the number of bytes needed to allocate.
Output
buffer	char []	The Nth channel in the index. If you pass NULL, this function returns the number of bytes needed to allocate.

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 negative value indicates an error. For this function, if you pass NULL for the buffer or 0 for the buffer size, this function returns the number of bytes needed to allocate.

int32 DAQmxGetNthTaskDevice (TaskHandle taskHandle, uInt32 index, char buffer[], int32 bufferSize);

Returns the Nth device. This function takes the taskHandle, index, and bufferSize you specify and returns the Nth device.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
index	uInt32	The Nth device you want to return. The index starts at 1.
bufferSize	int32	The size, in bytes, of buffer. If you pass 0, this function returns the number of bytes needed to allocate.
Output
buffer	char []	The Nth device in the index. If you pass NULL, this function returns the number of bytes needed to allocate.

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 negative value indicates an error. For this function, if you pass NULL for the buffer or 0 for the buffer size, this function returns the number of bytes needed to allocate.

int32 DAQmxTaskControl (TaskHandle taskHandle, int32 action);

Alters the state of a task according to the action you specify. To minimize the time required to start a task, for example, DAQmxTaskControl can commit the task prior to starting.

Input
Name	Type	Description
taskHandle	TaskHandle	The task used in this function.
action	int32	Specifies how to alter the task state.

Value		Description
DAQmx_Val_Task_Start		Starts execution of the task.
DAQmx_Val_Task_Stop		Stops execution of the task.
DAQmx_Val_Task_Verify		Verifies that all task parameters are valid for the hardware.
DAQmx_Val_Task_Commit		Programs the hardware as much as possible according to the task configuration.
DAQmx_Val_Task_Reserve		Reserves the hardware resources needed for the task. No other tasks can reserve these same resources.
DAQmx_Val_Task_Unreserve		Releases all previously reserved resources.
DAQmx_Val_Task_Abort		Abort is used to stop an operation, such as Read or Write, that is currently active. Abort puts the task into an unstable but recoverable state. To recover the task, call Start to restart the task or call Stop to reset the task without starting it.

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.