Xref: utzoo sci.electronics:10203 rec.audio:19373
Path: utzoo!utgpu!watserv1!watmath!att!cbnewsk!tob
From: tob@cbnewsk.ATT.COM (ted.o.burger)
Newsgroups: sci.electronics,rec.audio
Subject: Re: 2 way IR LED systems
Summary: HPs link is not two way
Keywords: HP calculator IR data communications
Message-ID: <2099@cbnewsk.ATT.COM>
Date: 20 Feb 90 19:38:31 GMT
References: <431@skipper.dfrf.nasa.gov> <6313@ncar.ucar.edu> <22296@uflorida.cis.ufl.EDU>
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 17

> In article <6313@ncar.ucar.edu> hpoppe@bierstadt.scd.ucar.edu (Herb Poppe) writes:
> >How about 2-way data communication (half or fuyll-duplex)?
> I think it's been done.  Some HP calculators have the ability
> to send data to the little HP printer via IR beam.  The printer
> checks for data corruption, and, if it detects an error, requests
> a retransmission.  Of course, this system requires a clear
> line of sight between sender and receiver, which would be a
Bob

Thr HP system is NOT a two way system.  The data is encoded in a (almost) full
error correcting format.  Their goal was to provide the link with minium cost to the
calculator so they could include it on the maximum number of calculators.
The calculator just has a single diode and the reciever is in the printer.
Only the people who want the printer have to spend the bucks to get the
IR receiver.

Ted