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FAQ: How do I interface with the EyeLink Host PC analog card?
#1
By default, the Analog card option of the EyeLink Host PC will output 3 channels (gaze x, gaze y, & pupil size) of analog data per eye recorded. The break out board provided with the system will have these channels split out into BNC connectors for easy interfacing with other analog recording devices.

The Analog card also has 16 bit digital input/output channels which can be utilized by the Host PC. The digital inputs may be defined as buttons, used for controlling the EyeLink tracker, or recorded to the EDF data file. Similarly, The outputs may be controlled by using ‘write_ioport’ commands sent from your Display PC via the dedicated Ethernet link, or used by the EyeLink tracker for data strobes and other functions. The command requires the port address (typically 4 or 5 for the analog card) and the 16 bit Hex value you want written to the card

Code:
#write_ioport <ioport> <data>
;;          <ioport>: byte hardware I/O port address
;;          <data>: data to write
write_ioport 0x4 0xFF

See Section 7.4 Digital Inputs and Outputs of the User Manual for more information on setting up the analog card for sending and receiving TTL triggers.