Recipes for generating output upon a trigger

Starting a sequence upon a trigger

Just as a recording can be delayed until a trigger condition is met, the same can be done for analog or digital output:

from picodaq import *
from picodaq.stimulus import Triangle, Train
import matplotlib.pyplot as plt

pulse = Triangle(3*V, 20*ms)
train = Train(pulse, pulsecount=5)
with AnalogOut(rate=100*kHz) as ao:
    ao[0].stimulus(train)
    ao.trigger(3, polarity=1)
    ao.run()

This can be combined with recording:

import numpy as np

with AnalogOut(rate=100*kHz) as ao:
    with AnalogIn(channel=0) as ai:
        with DigitalIn(line=3) as di:
            ao[0].stimulus(train)
            ao.trigger(3, polarity=1)
            ao.run()
            adata, times = ai.readall(times=True)
            ddata = di.readall()

As the example shows, only the first edge in the trigger line matters. After that, the stimulus sequence is autonomous.

Repeated stimuli following a sequence of triggers

Triggered output can be combined with episodic recording. For instance, to produce a 2-s long pulse whenever a trigger is received, you might write:

from picodaq import *
from picodaq.stimulus import Triangle, Train
import matplotlib.pyplot as plt

pulse = TTL(2*s)
with DigitalOut(rate=100*kHz) as do:
    do[0].stimulus(Series(pulse, traincount=5))
    do.trigger(3, polarity=1)
    do.episodic()
    do.run()

If you call episodic() after defining the stimuli, the episode duration is computed automatically.

To continue forever, specify traincount=0. Note that if you do something like:

do[0].stimulus(pulse)

The current implementation assumes a single output train, which means that only the first trigger pulse would cause a stimulus to be generated.

One further restriction applies: episodic output of continuous wave data through the sampled() method of AnalogOut and DigitalOut is not supported. However, the Wave stimulus shape may be used.

Repeated stimuli with recording

Naturally, this can be combined with recording as well: