[visionegg] working code for fMRI exp: comments please
- From: Christoph Lehmann <lehmann@xxxxxxxxxxxx>
- To: visionegg@xxxxxxxxxxxxx
- Date: Fri, 02 May 2003 16:55:37 +0200
Hi
Here the code (main loop) of a small visionegg project, which waits for
a trigger on the parallel port, after a received trigger it updates the
screen with the next stimulus, and all mouse-responses are logged in a
file with the RT (relative to the actual stimulus). Also all stimuli are
logged into a file with stimulus-name and onset-time
What do you think about the timing-quality?
--
while (not pygame.event.peek((QUIT,KEYDOWN))):
while (not pygame.event.peek((QUIT,KEYDOWN))):
#log the mouse response (which button, and RT)
for event in pygame.event.get(pygame.locals.MOUSEBUTTONDOWN):
if event.button == 1:
response_log.append(VisionEgg.time_func() - stim_onset)
response_log.append('left')
elif event.button == 3:
response_log.append(VisionEgg.time_func() - stim_onset)
response_log.append('right')
#poll the LPT for the TTL trigger, sent by the MR scanner
#only poll the lpt, if the last pulse went to 0
#(counter = pulslength of the TTL signal)
counter = VisionEgg.time_func() - stim_onset
if counter > 1.1:
input_value = raw_lpt_module.inp(0x379) & 0x20 #pin nr 12
#if TTL signal on lpt, increment the stim_index
if (input_value == 0) and (stim_index < num_images - 1):
stim_index = stim_index + 1
break #leave the loop and update the screen
# draw the stimulus
stimulus.parameters.texture = preloaded_texture_list[stim_index]
screen.clear()
viewport.draw()
swap_buffers()
stim_onset = VisionEgg.time_func()
if stim_index == 1: #if it is the first stimulus, log start time
start_time = stim_onset
--
Andrew, if I sync buffer-swapping: does the swap_buffers() code wait for
the vsync pulse, and therefore during this time I will have an
unprecision in the RT?
thanks for any feedback.
the only thing not working properly is the fact, that with the code
above I wait for a TTL signal going from 1 to 0. Unfortunately the port
doesn't detect a TTL going from 0 to 1. Any help appreciated.
Christoph
--
Christoph Lehmann <lehmann@xxxxxxxxxxxx>
University Hospital of Clinical Psychiatry
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