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PST Serial Response Box, Refresh Detector

Hello! I am trying to use the Refresh Detector connected to the PST Response Box to calibrate the monitor in the Monitor Center. The button box is connected to COM1 and the refresh detector is connected to a “six pin hooded IDH connector” on the pst box. “It connects to a polarity keyed matching plug and sensor for the video refresh detector system”, says the manual. When I click “Get Photometer” the result is “No photometer found”. Could you please help me figure out how to make it work? Thank you.

Hi, a photometer and that refresh detector are two entirely different things. The refresh detector generates a “button press” event on the PST box (I think button 6 or 7) when a certain luminance is exceeded, which can be used to detect stimulus on-/offset. It cannot be used to do any monitor calibration whatsoever.

Hello Richard, thank you for your reply. I apologize for the confusion, I am trying to learn many things simultaneously as I go.

So, Monitor Center calibration is about colors, if I understand it correctly now. What I need is to make sure that when a stimulus is presented on the monitor, there is no delay, that the timing of a stimulus on the screen is exactly (or with a marginal error) what it is been recorded by the system. I need it for the ERP experiments.

I assume the refresh detector can help me with that. So, my goal is to write a program which would flash the screen between black and white and compare the coded timing of a flash and the refresh detector responses. I run your pstbox demo and instead of pushing a button as stimuli occurred I covered and uncovered the refresh detector with my hand – since it is associated with button 7. It did not produce any responses. How do I catch the detector’s response? Thank you.

Thanks for the clarification.

You’re right, the photo sensor can be used for this.

It appears that support for 5 buttons, and 5 buttons only (corresponding to the 5 hardware buttons on the response box), is hardcoded in the current implementation. You could try to change the line in psychopy/iohub/devices/serial/ that says self._nbuttons = 5 to self._nbuttons = 7. I cannot test this right now, but this might just work and produce press and release events. Ideally we would change the implementation to generate light_on and light_off events, I guess…

Thank you for the idea. I’ll be able to test it only on Monday and I’ll post the result here then.

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Great. I can’t seem to find our refresh detector, so testing this thing critically depends on you now :wink: If this turns out to be working, I will propose some changes to be included in future releases of PsychoPy.

I did test it and it works. I run the \psychopy\demos\coder\iohub\serial\ example while covering the refresh detector with my hand and simulate the button response by briefly letting light in. It does collect responses from button 7.

Thank you!