Trigger error in low sample rate

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lbwair
Posts: 1
Joined: Wed Nov 28, 2018 10:26 am

Trigger error in low sample rate

Post by lbwair » Wed Nov 28, 2018 10:32 am

Hi,

I am a psychology student from VU Amsterdam. I am conducting EEG study with BioSemi equipment recently. However, I faced some problems. When I choose the sample rate lower than 2048, such as 512, the error trigger will send. The code (python) I use to send trigger is :

## Initial
try:
from ctypes import windll
global io
io = windll.dlportio # requires dlportio.dll !!!
except:
print 'The parallel port couldn\'t be opened'

## Function: Sending trigger
def sendCode(trigger, port=0x378):
global io
try:
io.DlPortWritePortUchar(port,trigger)
except:
print 'Failed to send trigger %s!'% trigger
pygame.time.delay(16)

You can check the figure of error trigger (actually I do not send code like 223, 31, 127):E6A00D9433FC53E8BA078050EB6F99BF.jpg

Would you please help me fix it,
Thank you everyone.
Attachments
E6A00D9433FC53E8BA078050EB6F99BF.jpg
E6A00D9433FC53E8BA078050EB6F99BF.jpg (28.8 KiB) Viewed 101 times

Coen
Site Admin
Posts: 924
Joined: Fri Mar 26, 2004 7:00 pm
Location: Amsterdam, Netherlands
Contact:

Re: Trigger error in low sample rate

Post by Coen » Wed Nov 28, 2018 12:42 pm

Use positive trigger logic (down-sampling uses OR function to calculate trigger of multiple samples)
Use "analog" trigger display to investigate the problem.

see viewtopic.php?f=7&t=1022

Best regards, Coen (BioSemi)

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