From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-01-07 17:48:44
--- In buildcheapeeg_at_yahoogroups.com, Doug Sutherland <wearable_at_earthlink.net> wrote:
> Andreas,
>
> Now you're speaking my language, the language of tiny,
> low power, unobtrusiveness. I want the whole EEG on my
> thumbnail, but then I want my whole system on my thumb
> nail (freaky thing is: it's getting close).
>
> > fits in less than 1/2 a euro-board. Don't expect the
> > through-hole version to be that small.
>
> Sounds awesome, but hard to build.
Not really, if your fine-motor skills are in order.
They say the secret is in the sauce. Well, in this case, it is in the
flux...
http://www.geocities.com/vk3em/smtguide/smtguide.htm
>
> > It runs on four 1.5V batteries.
>
> Assuming I already have regulated 5V from another
> supply (PT6302A) ... can I use that? My battery will
> be 12V, powering an embedded PC through 3A 5V
> switching regulator.
>
Hmm, it really does need a dual supply, so if you have -5V on hand
and regulate that and the +5V to +/- 3V...
The power-system is in a ever-changing state I'm afraid. Right now
I'm considering splitting up the amplifier and microcontroller so
that the amplifiers can run on higher voltages, but the minimum
requirement will probably remain +/- 2.5 or 2.7 volts.
> > I've cut away everything non essential, so forget
> > about expandability...
>
> Here's an idea. Leave two pins on the Uc set up for
> TTL serial to another uC. A second board can grab
What two pins? :-)
If you can do high-voltage (+12V) programming of AVR processors, the
reset pin can be used for I/O or as an analog input (EMG maybe?). But
other than that, there are no pins left. Ok, you can get rid of the
1kHz reference clock and free another pin, but the microcontroller's
internal oscillator has a 2% error margin....
Next step up from the ATtiny15 is AT90S4433...I think.
A better solution is probably to have another MCU "downstream" that
collects the data from different sources.
In this first prototype I will use a very simple 3-byte protocol:
First byte:
Bits 7-1: Left channel most significant bits
bit 0: sync bit = 1
Second byte:
Bits 7-1: Right channel most significant bits
bit 0: sync bit = 0
Third byte
Bits 7-5: Left channel least significant bits
Bits 4-2: Right channel least significant bits
bit 1: unused
bit 0: sync bit = 0
> PS. Please proto the TinyEEG to make sure it works.
No problems. As soon as I get the little snags sorted out...
/Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:36 BST