A Open Soure Time Course Synchronize Tool for Visual Psychophysics Experiments
Many visual psychophysics experiments need synchronize time course of visual stimuli with other data collected in the experiments, like EEG, MRI, etc. A software trigger under a non-realtime operation system, e.g. Linux or Windows, faced unexpected delay in order of magnitude from 10 to 100ms. A hardware trigger was need for a realtime synchronization which was normally provided by well designed visual stimuli presentation systems. Here I provided a open source tool, VisSync (https://github.com/VisionShilin/VisSync), to resolve this problem whitout need a pre-designed hardware interface and the hardware cost of the tool was less than 20 dollars. A photosensitive diode and an Arduino board were all we need. The photosensitive diode was placed on the corner of the display which was stimulated by a high intensity flash included in the visual stimuli. The program running on the Arduino board read pin-input from the photosensitive diode in realtime and triggered a physical synchronize signal to the output pin according to a pre-setting threshold value. The precision of the synchronization was in order of magnitude 1µs using a Arduino board with 16MHz CPU frequency.
