Execute code at a time offset in a loop in Builder

Builder
1

PsychoPy Builder components all have start and stop parameters to
control when stimuli are displayed, in particular this allows offsetting
the start of display.

I need to send a software event trigger at successive offset intervals from the start of the loop (whilst a video is playing).
This would be easy if it was a hardware trigger (eg using the parallel i/o component) but how can I easily do the same for a software trigger (to a separate application)?

I could use a code component and add code to run on every frame and monitor the time or count the number of frames but this is a pretty ugly solution.

2

It sounds like the sort of totally-custom use-case that absolutely needs a code component, but I donā€™t imagine it would be a very ugly one. For example, if you need something every 30 frames (0.5s) you could do this ā€œon every frameā€:

if frameN%30 == 0:
    win.callOnFlip(myParallalePort.setData, newValue)

Could you edit your post to indicate exactly what pattern of trigger timings you need?

3

A code component, ā€œrun every frameā€ with

if not frameN % 120:  # every 120 frames = 2 seconds on 60 Hz monitor
    # send software trigger here

looks OK? The % is a modulus operator in python. Itā€™s handy for this kind of interval-detection on an incrementing integer.

4

Thanks both. Thought I had another way executing $() code in teh text field of a text component however that is executed at the start of the repeat rather at the componentā€™s ā€˜startā€™ time, so I think Iā€™ll have to make do with the modulus approach.
(though a code component that permitted a delayed offset/execution time would be nice :slight_smile: )

5

You donā€™t have to use modulus maths to make this work - thatā€™s just a convenient way to know that the code gets run at a regular period.

You could also have:

#start of Routine
markSent = False

#each frame
if (someConditionHere) and not markSent:
    myParallelPort.setData(marker)
    markSent = True

Donā€™t worry that the if-statement is being run every frame - with regular components (like your text stimulus) that is being done anyway. The code above is essentially repeating the logic of standard components, except they have to track multiple ā€˜statusā€™ options rather than just sent/notsent.

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