A86: Re: Radio Link- Revisted and Problem Explained
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A86: Re: Radio Link- Revisted and Problem Explained
I went to my local Radio Shack (which is where
you got your parts from, right?), and asked if they had any radio transciever
components. They said that they had the parts to build my own transceiver,
but none pre-built, and then they tried to sell me a stupid two-way childs
walkie-talkie.... So part numbers would be very helpful, or at
least, the general frequency on which your transceivers opperate.
Please accept my
apologies for my unresponsiveness to earlier mail message,
after all, I
was going through finals week at my school. When I first posted
my
idea for a calculator radio link with 4 transcievers, I neglected
to
mention my specific reason for using that many radio parts and not
just as few
as possible.
The calculator uses a noninterruptable
protocal for it's link transmissions.
What the sending unit will do is
lower the power on one wire and wait for the
other end to lower the
opposite wire, the recieving unit will interpret a 1 or
0 depending on
which wire it was and upon lowering both wires, the sending
unit will
raise the power of both wires.
Now what all of this has to do with radio
links is this: the signal has to
be continuous or the calcs will
generate transmissions errors from timeouts on
the port. If the
signal is digitized through a modem, the lowering-raising
patterns will
skip points and accidentally lower the wires when they need
constant
voltage. This is why we can't digitize the calc links with
modems.
My calc radio link works perfectly fine for a range of about a
100 feet. It
gets very little problems during calculator TI-OS
transfers because the
raising-lowering patterns have great tolerance for
interferences. I'm
assuming ztetris has a linking routine similar
to the TI-OS because it causes
few problems. I have found that very
few linking routines for the TI-86, TI85
and TI92 use continuous
bitstream (where the recieving unit must keep up with
the transmitting
unit or perish the connection) flow, but rather the raising
and lowering
routines.
If somebody manages to comeup with a modem radio link that
supports
continuous transmission like most analog communications, that
would be great,
but I'm sticking with my 2 frequency version because it
is simple and concise.
In response to earlier questions, I don't know the
exact part # of the
transcievers, I got the kind that have four
prongs. One prong was input, one
was output, and two were the
negative and positive power leads.
The wiring of the power leads was more
than obvious. As for the other two
prongs, I first tried to wire
them directly to the calc wires themselves, but
that caused the calc's
LCD to go black (i.e. too much power!), so I grabbed
the extra 3.3K ohm
resistors I had from my old calculator serial port link and
wired the
output prong first to the resistor and then to the link. I
then
wired the input prong directly to the link. I don't know how
much more
powerful the flow from the transcievers was compared to the
link, but the
resistor configuration happened to work
perfectly. I want to find some
transcievers that have the
correct power output because I can't leave the link
on for more than
about ten minutes before it gets really hot. Oh well.
Tim
Adkisson
<A HREF="mailto:honorIam2@aol.com">honorIam2@aol.com</A>