From: Joerg Hansmann (info_at_jhansmann.de)
Date: 2001-05-20 13:11:35
Hi,
----- Original Message -----
From: Waldemar Neto <wpneto_at_o...>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Saturday, May 19, 2001 4:36 PM
Subject: Re: [buildcheapeeg] Re: Sound Card-Phase II
>Ok Joerg , thanks for information - one thing yet : if we plan to use the cheapEEG
> for real-time analysis purposes ( in Laptop or Desktops ) - like evoked potential
> task or EEG walking holter - does RS232 get too slow ?
On the RS232EEG side the uP samples 6 input channel voltages and sends
them via RS232 to the PC in a time interval of 1/256 Hz or 3.906 ms.
Because the AD-channles are not equipped with sample and hold but
instead are time-multiplexed there is a small delay that increases with the
channel number but never exceeds 3.9 ms. This channel number dependant
delay could be compensated by software on the PC-side with an interpolation.
After this compensation each channel will have the same constant delay of e.g. 5 ms.
I think this should be ok for evoked potential measurements, especially if you
record the stimulus on one of the spare channels or one of the 4 digital channles
provided by the RS232EEG.
> Sometimes I have already problems using (until ) parallel connection !
What OS are you using ? (I assume WIN9X ? )
Regards
Joerg
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