problem with sending different trigger to BrainVision Recorder with V-Amp, serial port

Lee

Dear community

Hi, I'm Lee, and it's my first time asking a question. Please understand If I'm not good at English.

I'm making simple oddball task for my ERP Experiment.

So I want to send different trigger at different stimuli.

but, BrainVision Recorder was received same trigger. just "S11".

at first, before start the experiment, I wrote the code like below at inline script(run).

import serial
import time

try:
	exp.port= serial.Serial('COM3')
	print 'serial port read', exp.port.name, exp.port.baudrate, exp.port.bytesize, exp.port.parity
except: 
	print 'serial port not read'

and the printed result of first inline script is here.

serial port read COM3 9600 8 N

and after each stimuli, I wrote the code like below.

value = var.triggervalue

t = time.time()
count = 0

try:	
	while (time.time()-t) < 0.005 : #500Hz: >4ms / 250Hz: >8ms
		exp.port.write(str(value)) # or whatever is appropriate
		count += 1
	print('trigger has been sent')
	print('value:',value,'    time:',time.time()-t,'    count:',count)
except:
	print 'trigger not sent'

self.sleep(200)

and the printed result is here. (value 1: prominent / value 2: odd)

trigger has been sent
('value:', 1, '  time:', 0.005000114440917969, '  count:', 58)

trigger has been sent
('value:', 1, '  time:', 0.00599980354309082, '  count:', 32)

trigger has been sent
('value:', 2, '  time:', 0.006000041961669922, '  count:', 36)

trigger has been sent
('value:', 1, '  time:', 0.006000041961669922, '  count:', 34)

trigger has been sent
('value:', 1, '  time:', 0.006000041961669922, '  count:', 67)

last, I end the experiment with this code

exp.port.close()

I expected this inline scripts would sent right trigger, but BrainVision Recorder received only "S11".

Why Recorder read the trigger only "S11", not "S1" nor "S2"? Where is "S11" from?

I read other forums(https://forumcogsci.nl/index.php?p=/discussion/491/solved-sending-different-triggers-via-serial-port etc), but I can't understand why and how I make mistake.

Could you explain what is wrong?

and I have one more question.

I send the trigger with "for" phrase, so I send lots of trigger at one time.

hhowcan I send the trig only one and long

If you could correct my mistake, I would be much appreciated.

eduard

Hi Lee,

I don't know how it works with serial ports, but when sending triggers through parallel ports, you have to unset after you changed a value. So every time you sent a value (say a 1), a little while later (for parallel ports ~10 ms) you send a zero. Like that you make sure that the triggers won't overlap or add up. Whether this is the reason why you only see S11, I don't know. Maybe you can experiment a little with the triggers (e.g. sending only number repeatedly, or sending different numbers than 1 and 2).

I send the trigger with "for" phrase, so I send lots of trigger at one time. how can I send the trig only one and long

I don't see where you used a for loop, but one straightforward way to adapt your code would be:

value = var.triggervalue

t = time.time()
count = 0 
trigger_sent= 0
try:	
	while (time.time()-t) < 0.005 : #500Hz: >4ms / 250Hz: 
                if trigger_sent == 0:
		    exp.port.write(str(value)) # or whatever is appropriate
		    count += 1
                    trigger_sent = 1
	print('trigger has been sent')
	print('value:',value,'    time:',time.time()-t,'    count:',count)
except:
	print 'trigger not sent'

self.sleep(200)

Eduard