DataAcquisition

Interface to data acquisition device

Description

The DataAcquisition object provides access to the devices of a specified vendor.

Creation

Use the daq function to create a DataAcquisition object.

Properties

AutoSyncDSA — Automatically Synchronize DSA devices

false (default) | true

Automatically Synchronize DSA devices, specified as a logical true or false. Use this property to enable or disable automatic synchronization between DSA (PXI or PCI) devices in the same DataAcquisition. By default automatic synchronization capability is disabled.

Example: true

Data Types: logical

Channels — Device channels

Read-only: array of channel objects

This property is read-only.

Device channels, returned as an array of channel objects. Create channels with the functions addinput, addoutput, and addbidirectional.

Example: addinput(d,…)

Clocks — Device clock connections

Read-only: array of clock objects

This property is read-only.

Device clock connections, returned as an array of clock objects. Create clocks with the addclock function.

Example: addclock(d,…)

DigitalTriggers — Device digital trigger connections

Read-only: array of DigitalTrigger objects

This property is read-only.

Device digital trigger connections, returned as an array of DigitalTrigger objects. Use the addtigger function to add digital triggers to the DataAcquisition.

Example: addtrigger(d,…)

DigitalTriggerTimeout — Time allowed for occurrence of digital trigger

10 (default) | numeric | duration

Time allowed for occurrence of digital trigger, specified as a numeric value in seconds or a duration.

Example: 30

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | duration

ErrorOccurredFcn — Callback function to call when error occurs

function handle

Callback function to call when error occurs, specified as a function handle.

Example: @mycleanup

Data Types: function_handle

LogToDisk — Specify TDMS file logging

false (default) | true

Control whether to log data to TDMS file, specified as true or false (default).

Example: dq.LogToDisk = true

Data Types: logical

LogFileMode — Write mode for logging to TDMS file

"append" (default) | "overwrite" | "new"

Write mode for logging to TDMS file, specified as a string or character vector. The following values are supported:

• "append" — Append data to existing file. Old data is retained; new data comes after old data in a new channel group.

• "overwrite" — Overwrite existing file with new data. Old data is lost.

• "new" — Create a new file. If the file already exists, an error occurs.

Example: dq.LogFileMode = "overwrite"

Data Types: char | string

LogFileName — Name of TDMS file for logging data

string | char

Name of TDMS file to log data to, specified as a string or character vector. The default file name is of the format "recording_YYYYMMDD-HHMMSS.tdms".

Example: dq.LogFileName = "MyDataFile_2.tdms"

Data Types: char | string

NumDigitalTriggersRemaining — Number of digital triggers remaining in run

Read-only: 1 (default) | numeric

This property is read-only.

Number of digital triggers remaining in run, returned as a double.

Example: 1

Data Types: double

NumDigitalTriggersPerRun — Number of digital triggers per DataAcquisition run

numeric

Number of digital triggers per DataAcquisition run, returned as a double.

Example: 2

Data Types: double

NumScansAcquired — Number of data scans acquired since the last start

Read-only: numeric

This property is read-only.

Number of data scans acquired in background operation since the last start, returned as a uint64 value. This value is reset each time start is called, and does not reflect whether the scans have been read into MATLAB.

Example: 1000

Data Types: uint64

NumScansAvailable — Number of data scans acquired and available for reading

Read-only: numeric

This property is read-only.

Number of data scans available for reading, returned as a uint64 value. These scans have been acquired by the device input channels in a background operation, but have not yet been read into MATLAB. The value decreases with each call to read; and is reset by a call to start.

Example: 1000

Data Types: uint64

NumScansOutputByHardware — Number of scans generated as device output

Read-only: numeric

This property is read-only.

Number of scans generated as device output, returned as a uint64 value.

Example: 1024

Data Types: uint64

NumScansQueued — Number of scans prepared for device output

Read-only: numeric

This property is read-only.

Number of scans queued to the device output channels, returned as a uint64 value.

Example: 4000

Data Types: uint64

Rate — Data scan rate

numeric

Data scan rate, specified as a numeric value of samples per second.

Example: 44100

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

RateLimit — Lower and upper scan rate limits

Read-only: array of doubles

This property is read-only.

Lower and upper scan rate limits, returned as a 1-by-2 vector of doubles indicating minimum and maximum allowed scan rates in samples per second. The scan rate limits depend on the hardware and its configurations. In devices that multiplex channels to a converter, the rate limit is impacted by the number of channels you use. For more information, see Sampling.

Example: [8000 192000]

Data Types: double

Running — DataAcquisition running indication

Read-only: true | false

This property is read-only.

DataAcquisition running indication, returned as true or false.

Example: true

Data Types: logical

ScansAvailableFcn — Callback function when scans are available

function handle

Callback function to execute when scans are available from the input channels, specified as a function handle

Example: @read

Data Types: function_handle

ScansAvailableFcnCount — Number of acquired scans to trigger ScansAvailableFcn

numeric

Number of acquired scans to trigger ScansAvailableFcn, specified as a numeric value. The function handle specified in ScansAvailableFcn executes every time ScansAvailableFcnCount scans are acquired from the input channels. The default value is 1/10 the rate and the lower limit is 1/20 the rate of the corresponding DataAcquisition object.

Example: 8000

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

ScansRequiredFcn — Callback function when output scan data is required

function handle

Callback function to execute when scan data is required for device output channels, specified as a function handle.

Example: @write

Data Types: function_handle

ScansRequiredFcnCount — Number of scans to trigger ScansRequiredFcn

"auto" (default) | numeric

Number of queued scans to trigger ScansRequiredFcn, specified as a numeric value or "auto". The function handle specified in ScansRequiredFcn executes when NumScansQueued drops below the value specified in this property. The default value is 1/2 the rate and the lower limit is 1/20 the rate of the corresponding DataAcquisition object. If this property is set to "auto", it resets to the default value.

Example: 2000

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | char | string

UserData — Custom data

any data

Custom data, specified as any MATLAB^® data type and format.

Example: datetime('now')

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | struct | table | cell | function_handle | categorical | datetime | duration | calendarDuration | fi

Vendor — Data acquisition hardware vendor information

Read-only: vendor object

This property is read-only.

Data acquisition hardware vendor information, returned as a vendor object with the following properties:

ID
FullName
AdaptorVersion
DriverVersion
IsOperational

This object is the same as the corresponding vendor object returned by the daqvendorlist function.

WaitingForDigitalTrigger — Digital trigger waiting indication

Read-only: false (default) | true

This property is read-only.

Digital trigger waiting indication, returned as a logical.

Example: true

Data Types: logical

Object Functions

addinput	Add input channel to device interface
read	Read data acquired by hardware
readwrite	Simultaneously read and write device channel data
start	Start DataAcquisition background operation
stop	Stop background operation
removechannel	Remove channel from device interface
flush	Flush DataAcquisition input and output buffers
write	Write output scans to hardware channels
preload	Queue scan data for device output
addoutput	Add output channel to device interface
addbidirectional	Add digital bidirectional channel to device interface
resetcounters	Reset hardware scan count for all counter inputs
addclock	Add clock connection to device interface
removeclock	Remove clock from device interface
addtrigger	Add trigger connection to device interface
removetrigger	Remove trigger from device interface

Examples

Create a DataAcquisition

Create and configure a DataAcquisition object for interfacing with National Instruments™ devices.

d = daq("ni")
d.Rate = 20000;

Version History

Introduced in R2020a