Parallel Port Out Component

This component allows you to send triggers to a parallel port, USB2TTL8, or LabJack U3 device.

An example usage would be in EEG experiments to set the port to 0 when no stimuli are present and then set it to an identifier value for each stimulus synchronised to the start/stop of that stimulus. In that case you might set the Start data to be $ID (with ID being a column in your conditions file) and set the Stop Data to be 0.



Everything in a PsychoPy® experiment needs a unique name. The name should contain only letters, numbers and underscores (no punctuation marks or spaces).

Start :

The time that the stimulus should first appear. See Defining the onset/duration of components for details.

Stop :

Governs the duration for which the stimulus is presented. See Defining the onset/duration of components for details.


What information to save, how to lay it out and when to save it.

Start data0-255

When the start time/condition occurs this value will be sent to the parallel port. The value is given as a byte (a value from 0-255) controlling the 8 data pins of the parallel port.

Stop data0-255

As with start data but sent at the end of the period.

Sync to screenboolean

If true then the parallel port will be sent synchronised to the next screen refresh, which is ideal if it should indicate the onset of a visual stimulus. If set to False then the data will be set on the parallel port immediately.


Parameters for controlling hardware.

Port addressselect the appropriate option

You need to know the address of the parallel port you wish to write to. The options that appear in this drop-down list are determined by the application preferences. You can add your particular port there if you prefer.

RegisterU3 register to write to

When using a LabJack U3, you can select which register is used to write a data byte to. Register EIO is the default.

See also

API reference for U3

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