Data Acquisition Toolbox

Device-Specific Hardware Triggers

Most data acquisition devices possess the ability to accept a hardware trigger. Hardware triggers are processed directly by the hardware and are typically transistor-transistor logic (TTL) signals. Hardware triggers are used when speed is required because a hardware device can process an input signal much faster than software.

The device-specific hardware triggers are presented to you as additional property values. Hardware triggers for National Instruments and Agilent Technologies devices are discussed below and in Base Property Reference.

Note that the available hardware trigger support depends on the board you are using. Refer to your hardware documentation for detailed information about its triggering capabilities.

National Instruments

When using National Instruments hardware, there is an additional analog output trigger type available to you -- digital triggering.

If TriggerType is set to HwDigital, the trigger is given by an external TTL signal that is input directly into the hardware device. The following example illustrates how to configure a hardware digital trigger.

• ao = analogoutput('nidaq',1);
  addchannel(ao,0:1);
  set(ao,'TriggerType','HwDigital')
  

With this trigger configuration, ao will not start outputting data until the TTL signal is detected by the hardware on the appropriate pin.

The diagram below illustrates how you can connect a digital trigger signal to an MIO-16E Series board. PFI6/WFTRIG corresponds to pin 5.

Agilent Technologies

When using Agilent Technologies hardware, there are additional analog output trigger types that you must be aware of: digital triggering on a positive edge and digital triggering on a negative edge.

If TriggerType is HwDigitalPos, the trigger source is the positive edge of a digital signal. If TriggerType is HwDigitalNeg, the trigger source is the negative edge of a digital signal.

In both cases, the digital signal is an external TTL signal that is input directly into the hardware device. The example below illustrates how to configure such a trigger.

• ao = analogoutput('hpe1432',8);
  addchannel(ao,1);
  set(ao,'TriggerType','HwDigitalPos')
  

With this trigger configuration, ao will not start outputting data until the TTL signal is detected by the hardware.

When Did the Trigger Occur?

Events and Callbacks