Cool: Re: TI-H: Radio/Infrared/Laser Communications

To: ti-hardware@lists.ticalc.org
Subject: Cool: Re: TI-H: Radio/Infrared/Laser Communications
From: Grant Stockly <gussie@alaska.net>
Date: Sun, 1 Nov 1998 00:53:08 -0900
Delivered-To: ti-hardware-outgoing@towerguard.unix.edu.sollentuna.se
In-Reply-To: <19981031235929.15314.qmail@hotmail.com>
Reply-To: ti-hardware@lists.ticalc.org


>You've never built a transmitter or receiver before? There are plenty of
>schematics on the web for them, but IS the TI-xx bi directional?
>I thought there was only one data line, and if you hooked up a t/r to
>it, then it would get an infinite loop of signals... I am not exactly
>sure about the TI part...

What needs to be done is a standard for 2 wire unidirection per wire
format.  A way of encoding each lines input and output.

Like this...


in this format, the red wire in calc A is high (other is low), and the
white wire in Calc B is low (other is high).

Then software handshake of say...5 '$69's  ;)

$00 low
$FF high
                  RED  WHT  HDS  HDS  HDS  HDS  HDS  RED  WHT
        Trans     $FF, $00, $69, $69, $69, $69, $69, $FF, $00....  Receive
Calc A                                                                   Calc B
        Receive   $00, $FF, $69, $69, $69, $69, $69, $00, $FF....  Trans

I guess the # of Handshakes could be reduced, but then whats to do for the
rest of the night?  ;)

Okay...so do you get the point?  We need 2 freqs, but only one
transmitter...  Oh..and a cheepo $2.50 avr that can be programmed from 4
wires off a parallel port...

I'll draw up the AVR code...  Won't be hard at all...

Grant

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