Port objects are optional. You only need to add them if you want to change properties from default. Note you can also change the default values themselves using pb_prefs at the MATLAB command line, which may be more convenient.
An object of type port provides options for a serial port for general I/O use, e.g. by a portSender or portReceiver element. You can add columns setting properties for one or more port objects in the optional table for objects not specific to trial (experiment, device, staircase objects). [Or in the coding method: Make port objects outside trials using function portObject, set properties, and input them to addToExperiment.]
All objects
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No default, changeable in pb_prefs
A string that is the name of the serial port, as accepted by Psychtoolbox IOPort('OpenSerialPort'). From Psychtoolbox documentation: On Windows this could be, e.g. <cds>"COM1"<cds>, <cds>"COM2"<cds>, etc.; on Mac it is a path to a BSD device file, e.g. <cds>"/dev/cu.usbserial-FT3Z95V5"<cds> for a serial-over-USB device with unique ID FT3Z95V5; on Linux e.g. <cds>"/dev/ttyS0"<cds> for the first real serial port, <cds>"/dev/ttyUSB0"<cds> for the first serial-over-USB device, etc.
Default, changeable in pb_prefs: none
A string that goes to Psychtoolbox IOPort('OpenSerialPort') input configString. See IOPort('OpenSerialPort') for more information.