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FAQ: How do I interface with the EyeLink Host PC analog card?
Sam
Research Support Specialist
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Joined: Aug 2020
Posts: 1,015

#1
09-09-2020, 02:52 PM
The optional Analog card for the EyeLink Host PC provides a way to stream the gaze data as analog voltages, as well as send and receive TTL signals between the eye tracker and other lab equipment.
  • Analog Output
    By default, the card outputs three channels of analog data for each eye being tracked:
    • Gaze X position
    • Gaze Y position
    • Pupil Size
    The included breakout board provides standard BNC connectors for these channels, making it easy to connect to other analog recording devices.

  • Digital Input/Output (I/O)
    The card also features 16 digital channels for two-way communication.
  • Digital Inputs: You can configure the inputs to function as a response button box, allowing participant responses to be sent directly to the Host PC. These digital signals can also be recorded as markers in the EDF data file.
  • Digital Outputs: You can control the outputs from your Display PC by sending write_ioport commands. This allows your experimental script to send TTL signals to synchronize with other equipment. The command requires the port address (typically 4 or 5 for the analog card) and the 16-bit Hex value you want to send.

    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.