Hacking TI Calculator Interface

From: Richard A. Cini, Jr. <rcini_at_msn.com>
Date: Thu Jul 31 09:27:20 1997

On Thu, 31 Jul 1997 00:39:13 -0400, Roger Merchberger <zmerch_at_northernway.net>
wrote:


>>Use a diode to change the -12V to 0V, and resistors to change the +12V to
+5V .. it helps to have a cable to test first for that one, tho. On the
Tandy PDDs, the resistor value was 22K Ohms IIRC and any cheap .6V drop
diode would do (read: 1N914 -- everybody's buddy)<<

        It's funny that you said this. I just looked at an RS-232 level shifter
circuit on the MIT MiniBoard robotics controller that used a transistor, two
LEDs and a handful of resistors to accomplish that, but it needs 5v to
operate. Really what I need is a parasitic converter that's powered off of the
serial port itself. I've seen this done with a MAX232 or a Dallas 12?? chip.
Hmmmm, time to circuit-hunt.

-------------------------------------------------
Rich Cini/WUGNET
 e-mail: rcini_at_msn.com
 - ClubWin Charter Member (6)
 - MCPS Windows 95/Netowrking
Received on Thu Jul 31 1997 - 09:27:20 BST