frequency of cursor position recording

[Paul Groot]

Well, if you would like to keep in sync with the refresh cycle of the
monitor, you should go for the Display.WaitForVerticalBlank function
instead of using a fixed sleep duration. A combination of the sleep
and display.CalculatedRefreshDuration functions will also work, but
that construction will not stay in phase with the real refresh cycle.
(Although this is not very critical for tracking mouse position.)

P.

2011/3/28 Ashtyster <ashtyster at gmail.com>:
> Hi Paul,
>
> thank you for your reply.
>
> So if I understand you correctly, I should just calculate temporal
> resolution from the output, and adjust the sleep value according to
> the temporal resolution I'd like to have?
>
> All best,
> A.
>
> On Mar 25, 11:54 pm, Paul Groot <pfc.gr... at gmail.com> wrote:
>> Hi Ashtyster,
>>
>> The sleep instruction simple puts the running script in 'idle'mode for
>> the specified number of milliseconds. Windows can use this time to
>> allow other processes to consume some CPU time. This construction is
>> often used in loops to prevent the system to become stalled. A
>> duration of about 20 milliseconds might be sensible on systems that
>> are connected to a display at 50Hz. The value could even slightly less
>> on systems with a typical refresh rate of 70-80Hz. However, windows
>> will probably update the mouse cursor position completely independend
>> of the refresh cycle, so the temporal resolution might be very
>> different...
>>
>> Also, the DoEvent function is probably a leftover from the standard
>> basic language. It is used to allow other applications to handle the
>> message queue. I would normally not include this call in eprime
>> experiments.
>>
>> best,
>> Paul
>>
>> 2011/3/25 Ashtyster <ashtys... at gmail.com>:
>>
>>
>>
>>
>>
>>
>>
>> > Hi!
>>
>> > I've gotten a bit confused trying to understand how to set the
>> > frequency of cursor position recording in E-Prime.
>>
>> > I am presenting images and recording mouse cursor positions while
>> > subjects view the images. I would like to set the "sampling rate" for
>> > the cursor position recording to 50 Hz. The in-line script has the
>> > following sampling rate preset:
>>
>> > 'Give some time back (required) - i.e. sampling rate.
>> > Sleep 20
>> > DoEvents
>>
>> > What I am confused about is what does this '20' value mean? Does it
>> > mean 20 cycles per second?
>>
>> > I would appreciate if somebody could answer this question.
>>
>> > All best,
>> > Ashtyster
>>
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