Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!microsoft!alonzo
From: alonzo@microsoft.UUCP (Alonzo Gariepy)
Newsgroups: comp.sys.handhelds
Subject: Re: HP28 IR link
Keywords: hp28 IR LED
Message-ID: <9007@microsoft.UUCP>
Date: 13 Nov 89 18:35:23 GMT
References: <2444@gmu90x.UUCP> <8538@microsoft.UUCP> <13512@orstcs.CS.ORST.EDU> <8615@microsoft.UUCP> <13672@orstcs.CS.ORST.EDU>
Reply-To: alonzo@microsoft.UUCP (Alonzo Gariepy)
Organization: Microsoft Corp., Redmond WA
Lines: 16

In article <13672@orstcs.CS.ORST.EDU> daver@guille.ECE.ORST.EDU (Dave Rabinowitz) writes:
> There are two bits which control the LED.  One turns on the LED modulated by
> the carrier, producing the 32768Hz signal, but the other turns on the LED
> independently of the oscillator.  A program which used this bit and toggled it
> fast enough (12uS on, 13uS off) could generate a 40KHz signal.  Be very
> careful!  The LED drive circuit assumes the LED will be on with well under a
> 50% duty cycle, so if you turn on the LED and leave it on accidently you could
> potentially damage the electronics.

Do you have the address of these bits?  It would save me a great deal of
effort.  Thanks for the clear explanation.  The warning about duty cycle
is very much appreciated; one could do this quite accidentally and lose
use of the LED.

Alonzo Gariepy
alonzo@microsoft