Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!microsoft!alonzo
From: alonzo@microsoft.UUCP (Alonzo GARIEPY)
Newsgroups: comp.sys.handhelds
Subject: Re: Easy HP infra-red PC receiver.
Message-ID: <10169@microsoft.UUCP>
Date: 6 Jan 90 01:47:05 GMT
References: <5916@sdcc6.ucsd.edu>
Reply-To: alonzo@microsoft.UUCP (Alonzo GARIEPY)
Organization: Microsoft Corp., Redmond WA
Lines: 34

In article <5916@sdcc6.ucsd.edu> pa1409@sdcc13.ucsd.edu (Steven Haehnichen) writes:
| I recently ran across a gadget at Radio Shack that seemed too easy
| to be true, and still might be.  It's their "GP1U52X Infrared
| Receiver/Demodulator"  (Catalog # 276-137). 
| 
| Ok.. The three pins are GND, Vcc, and Vout... simple, eh?
| I connected the Vout to the Error line of my PC's parallel port
| and put an LED on it just for looks.  I stole the +/- 5 VDC from
| the key-board port and that was it.
| 
| BUT... Does it pick up HP-IR?  Yup. Along with every IR remote
| control I own. 
| 
| If you set it up so that the input is fed into the Error line of the
| parallel port (like mine), the fourth bit of port 0x379 will be 0 on an IR
| pulse. (first bit being the LSB) so something like this works to
| read it: (Turbo C)
| 
| IR = !(inportb(0x379) & 8)
| 
| Where IR is true on a IR pulse.

Chances are that this device will not work with the HP-28.  Modulation 
involves transmission of information on top of a carrier frequency.  
The frequency of the carrier used by the HP-28 is different than that 
used by remote controls.  Unless this device is smart enough to detect 
the carrier and switch (very unlikely), it won't properly detect the 
signal (although I am sure a great deal of noise will be generated).  
The other problem is that the signal from the HP-28 is very dependent 
on timing.  You need more than just pulse detection, and you need very 
accurate timing information.

Alonzo Gariepy
alonzo@microsoft