From: Waldemar Neto (wpneto_at_o...)
Date: 2001-05-20 16:56:49
Hi Joerg,
3.9 ms is a very good delay and the interpolation idea too.
Maybe be fine to do a simple test for real time on pragmatic effects on RS232 processing ( with any device feeding data - eg. calculator sending a senoidal function ) putting a short routine to see and watching the performance . If you already did it ( or saw it ) then there's no problem; otherwise, the practical effects may bring surprises (especially for Windows' "misjudgement bandwidth ")
One more thing: joining with the cheap eeg idea , would it be good to allow using DOS too ( for retrieve old PCs XT up to 486 ) ? Just wondering that it could amplify the beneficts of the project .
----- Original Message -----
From: Joerg Hansmann
To: buildcheapeeg_at_yahoogroups.com
Sent: Sunday, May 20, 2001 9:11 AM
Subject: Re: [buildcheapeeg] Re: Sound Card-Phase II, real-time analysis
>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 evokedpotential
> 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 ofe.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 ? )
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:30 BST