From: Brian Gr (brian_gr_at_hotmail.com)
Date: 2002-01-18 03:53:58
With a 256 Hz sample rate, 112Kb will support about 20 16 bit channels withone 16 bit sync word per frame. I would suggest rs232 is adequate for the current project. A QEEG type project with > 20 channels would require higher capacity channel, but one should ensure a project doesn't become 'gold plated' i.e. if the project scope creeps, so will the time to realize deliverables.
Brian
> > other interfaces (USB, Firewire, IrDA, whatever), which might
> > be needed when increasing the number of
> > channels and discovering that RS232 is not fast enough
>
> The device that I built ran at 9600 Baud and transmitted 5
> bytes at a 128 Hz rate. That worked as well or better than
> most machines out there. So what is this USB, Firewire, IrDA for?
> I thought you wanted a CHEAP brain monitor.
I would prefer a SCALABLE brain monitor. The basic modules
should preferably be inexpensive of course.. USB, Firewire,
etc are just examples of interfaces that may be needed /
wanted for some applications. For EEG "brain mapping" you
need quite a few channels (like 32 or even up to 128).
> So as not to keep this argument going for another few months, the
> present goal is to transmit RS232 data at 112.2 K Baud over
> fiber optic isolated transmitter receiver pairs. We will be able
> to satisfy the safety isolation ( 5,000 volts ) requirement with
> a 2 inch length of fiber. The transmitter and receiver will be
> on separate boards. Andreas has picked out the chips that should
> just "bolt" together, and we all agree that this is not the lowest
> cost solution, but should work without fiddling.
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