Making a good antenna seems like the hardest part - a big ferrite
loopstick?

Cheerful regards,

Bob


On Thu, 18 Sep 2008 11:52:27 -0400, "Walter Banks"
<walter@bytecraft.com> said:
> Bob,
> 
> The original implementation was done on a Sanyo 5800 series CMOS
> 4 bit processor that was used for watches and small PDA's and in
> this case store labels. the processor was used because it was low power
> and an internal gate array that was designed to drive LCD segments.
> It will take some looking for the implementation notes here, its here
> we moved and the old mental index doesn't work here. The basic
> implementation sync'd the serial data with the carrier frequency. The
> carrier was 32.768Kz. I can't remember the data rate carrier /8 or 16
> maybe / 32. The data was manchester encoded so the carrier did a
> 180 deg shift on a data transition. The links were half duplex
> bi-directional with a range of about 300 feet in an electrically noisy
> environment .
> 
> The transmitter consisted of two output pins on the micro that
> always complimented each other to drive the tuned circuit that
> served as an antenna.  Data was added by exoring 11 with the
> port mask that was being output.
> 
> Input used the same two pins and a software detect of the phase
> shifts .
> 
> The system had a low data rate and enough redundancy to be
> quite reliable. It also had a layer of error correcting in the protocol.
> 
> When I get a chance I will pull notes. We used a similar system
> on a wireless transmitter that reported data out of an instrumented
> tooth brush (forces and direction information for a research project)
> 
> 
> 
> w..
> 
> 
> 
> 
> 
> 
> Bob Blick wrote:
> 
> > On Wed, 17 Sep 2008 17:26:49 -0400, "Walter Banks"
> > <walter@bytecraft.com> said:
> > > The Tx/Rx had everything in software.
> > >
> > > Yep bit banged RF
> >
> > That is way cool. I'd love to actually do something like that. Is there
> > any documentation or more info around?
> >
> > Thanks,
> >
> > Bob
> 
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