Engineering Design NIDisk Guía de usuario descargar pdf (Pagina 21)

NIDisk User Guide

the display. The total headroom value is reflected in both the numerical readout and bar

display.

8. Acquisition and Playback Triggering

Triggering NIDisk from an External System

External triggering allows the user to initiate acquisition or playback in NIDisk via an

external control signal, in order to synchronize the NIDisk I/O process with an external

system. For example, an external system might begin neural data acquisition, collect pre-

trigger data for 5 seconds, then issue a trigger to NIDisk to begin playback stimulation. This

"hardware" triggering provides very high accuracy, typically on the order of 1 microsecond,

which is much more accurate than synchronizing the two systems from the keyboard.

Trigger signal

The external control signal is called EXT_TRIG. National Instruments (NI) boards typically

require a TTL-compatible trigger signal with a minimum duration of 10 nsec. Most NI

boards can trigger on either a rising or falling trigger signal, as specified by the Trigger

polarity parameter. This is useful because some external systems can provide only one type

of polarity. Be sure to consult the trigger specs of your specific I/O board, then confirm

that the external system can output a compatible trigger signal.

Trigger signal latency

Trigger latency is the time delay between the external trigger and the beginning of the

triggered I/O process. It is board-dependent but not CPU-dependent, and is typically < 1

microsecond.

Trigger signal connections

If you have an Engineering Design (ED) I/O panel, connect the external trigger to the TRIG

IN connector on the panel. If your ED panel does not have this connector, contact ED for

modification options.

If you have a National Instruments (NI) I/O panel, connect the external trigger to pin PFI-1.

Triggering instructions

To perform external triggering:

1. Connect the external trigger signal as described above.

2. On the acquisition or playback parameter screen in NIDisk, select External triggering,

then select the trigger polarity.

3. Click OK on the acquisition or playback summary screen. NIDisk will prepare the I/O

process and display a blank Acquiring data or Playing data box.

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 35 36

Sin comentarios

Engineering Design NIDisk Guía de usuario Pagina 21