Delay between parallel port trigger and photodiode measured display onset

[Michael]

Have you tried reading though similar posts already on this forum?

EGI Netstation - visual timing latencies

Hi, as far as I know, the best way to synchronize with the EGI is to implement an NTP client which connects to the NTP server running on the Netstation machine and keeps updated a local clock. By this way, there’s no need to explicitly send a sync command at the beginning of each trial (which by the way comes at the cost of an RTT): you just query the local clock. Some while ago (as part of the PsyScope project) I’ve implemented a little C module (and relatile python wrapper) that does exactly …

@gernot

The same results can be reproduced using a Matlab script, such that it is probably not the presentation software that is causing the problem

If the signal is somehow arriving “before” the stimulus is displayed, then yes, that likely indicates a problem with time synchronisation, as in the thread above.