From: yaniv_vi_at_yahoo.com
Date: 2000-12-22 13:13:24
--- In buildcheapeeg_at_egroups.com, "Joerg Hansmann" <jhansmann_at_g...>
wrote:
> Hi,
>
> ----- Original Message -----
> From: <yaniv_vi_at_yahoo.com>
> To: <buildcheapeeg_at_egroups.com>
> Sent: Wednesday, December 20, 2000 7:22 AM
> Subject: [buildcheapeeg] to jeorg - about the infrared com ?
>
>
> > hi joerg
> > did you checked the irx board (and schematic ) for cheap efficent
> > irda comm ?
>
> Yes. I took a look at it.
> The IS1U20 irda receiver utilized in the circuit is very
interesting, because
> it performs pulse stretching for direct interfacing to a normal
uart-input.
> However SHARP writes in their datasheet, that IS1U20 is not
recommended
> for new design.
what does this mean ?
is there a problem to reuse this tested design ,you think ?
> The irda-Transmitter side is the worst part: A simple IR-emitter-
LED has to
> be pulsed with 3/16 of the baud-rate and that is obviously done by
> the pic16f84 per software.
>
> Lets assume baud=115200
> XTAL=10Mhz -> PIC instruction cycle time = 400 nSec
>
> A 3/16 baudrate pulse would be 1.628uSec and that would be only 4
instructions
> on the PIC. For processing one complete bit 21 instructions would
be used.
> That means timing is very critical and the communication could
probably
> be only half-duplex.
comm is only half duplex .
is it a problem ? your protocol isn't half duplex ?
>
> The AT90S4433 at ca. 7Mhz is nearly 3 times faster than the PIC at
10Mhz,
> however I make use of about 3 interrupts and want to use full duplex
> communication. So generating irda pulses in software is a concept
> I do not like very much.
>
> > when comparing it to the other alternative - take in nthe option
that
> > is the irx board you can use the irda c code in the ateml
processor .
>
> C code for PIC/Atmel will not be very portable because it is very
> machine dependent.
>
> > here's the address :
> >
> > http://www.media.mit.edu/~r/projects/picsem/irx2/
> >
> >
forget reusing code , is it just for 1st version -
faster and easier and cheaper option for you to amke irda connection ?
> > and another thing :
> > maybe now is the time to start integration check (of crrent
version)
> > with a biofeedback practicioner ?
>
> Perhaps a biofeedback practitioner could give some hints about
> feedback-protocols etc.
>
> > to ask him what he think of the sw and hw ?
>
> sw: that is the part of Rob.
>
> hw: It is still a raw pcb with some cables lying on my desktop.
>
> How should the integration check look like ?
let's assume for a minute you have a box and laptop is safe .
you or maybe rob (does he have a bfb machine ) should go to
bfb practicioner willing to help.
and use maybe basic software , but talk to him / check
with him about all aspects of h.w. - what does he think of
them - especially for personal use .
but i don't think it's need overstressing , because first
version won't be 100% - the next ones will be better with alot of
user feedback .
and also taLK WITH him about safety .
>
> > and in paralellel work on remaining h.w. subjects .
>
> A problem is safety.
> Recently there was a thread about bio-signal amplifiers on
de.sci.electronics
> One question was, wheather a battery powered laptop connected to an
EEG
> with optocouplers would be safe:
> The answer was : NO.
> Because in a Laptop high voltages are generated for display
background
> illumination. Under worst case conditions those voltages can kill a
test subject
> connected to the EEG.
>
o.k. so first we should make irda . but all the
devices i know use optocouplers and have fda approval .
so what's the reliability of this info ?
maybe it's depends on breakdown voltage of the optocouplers ?
but that's not so important because we'll make irda one .
and btw - i don't heard of anybody hhurt from this kind
of mallfunction yet .(just btw - not as rule)
> Even if the EEG is fully battery powered, the battery voltage of
let us assume 12VDC
> could lead to severe health damage if connected with low impedance
electrodes
> (like EEG-Electrodes) to the test subject.
> 10uA is the maximum current allowed under any condition.
> The existing design can not guarantee this and must therefore be
revised.
there 's one thing i dont' know
1. is this one of the things the fcc checks ?
2. what's exatly needs to be changed to make it safe and how hard it
will be ?
3. it seem that in life there are many potential 10UA sources ,
so this claim seem very very strict .
>
> > it may be possible to get somebody to help you , would you like
it ?
>
> Yes of course.
>
> Regards,
>
> Joerg
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:28 BST