Generate Digital Data Using a Shared Clock

This example shows how to share the clock with the analog input subsystem on your device with the digital subsystem to generate clocked data that is automatically synchronized. You do not need any physical connections to share the clock. For more information, see Automatic Synchronization.

Create a DataAcquisition object and add a digital output line from port 0 line 0 on Dev1. This example uses a NI USB-6351 with device ID Dev1.

d = daq("ni");
addoutput(d,"Dev1","Port0/Line0","Digital")

Note

Not all devices support clocked digital I/O operations with hardware timing. For these devices you can use software timed operations with single scan calls to read and write.

Devices that support clocked digital I/O operations might not support them on all ports. Check your device specifications.

Add an analog output channel to your DataAcquisition object using the addoutput function.

addoutput(d,"Dev1",0,"Voltage");
d.Channels

ans = 

    Index    Type     Device       Channel       Measurement Type          Range                  Name       
    _____    _____    ______    _____________    ________________    __________________    __________________

      1      "dio"    "Dev1"    "port0/line0"    "OutputOnly"         "n/a"                 "Dev1_port0/line0"
      2      "ai"     "Dev1"    "ai0"            "Voltage (Diff)"    "-10 to +10 Volts"    "Dev1_ai0"

The device generates digital data at the scan rate determined by its analog subsystem. Configure the scan rate and specify the data to output. In this example, 200 samples of digital data is generated in 2 seconds.

d.Rate = 100;
Tsec = 2;
dataAO = zeros(Tsec*d.Rate,1);
dataDO = randi([0 1],Tsec*d.Rate,1);

Output the generated digital data to the hardware channel using the write function.

write(d, [dataDO dataAO]);

You can check the NumscansOutputByHardware property to verify that the device has generated the specified data.

d

d = 

DataAcquisition using National Instruments(TM) hardware:

                     Running: 0
                        Rate: 100
           NumScansAvailable: 0
            NumScansAcquired: 0
              NumScansQueued: 0
    NumScansOutputByHardware: 200
                   RateLimit: [0.1000 2.8571e+06]

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