Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uunet!mcsun!hp4nl!cwi.nl!jurjen
From: jurjen@cwi.nl (Jurjen NE Bos)
Newsgroups: comp.sys.handhelds
Subject: HP48 and IR remote control: request for help
Keywords: Remote control, IR, HP48
Message-ID: <3632@charon.cwi.nl>
Date: 4 Jun 91 09:44:26 GMT
Sender: news@cwi.nl
Organization: STORC, Veldhoven
Lines: 17
Originator: jurjen@lijster.cwi.nl

About once a week, we get a request to convert our HP28 remote control program
to the HP48.  We have not succeeded in doing this yet.

The main reason that we did not succeed, is that the proper way to control the
hp48's IR LED has not been found.
A while ago somebody posted that bit 3 of address #11C controls the LED, but
this is not useable for a remote control for two reasons:
- The LED is turned on unmodulated, while a remote control needs a 30kHz
    modulated signal to work properly.  (Actually, I wrote a remote control
    program using unmodulated signals, and it works over 6 cm, no more.)
- The LED is not always turned on if the bit is set, so that the resulting
    program has unpredictable behaviour.  There is probably a disabling
    circuit that we do not know of.

Does anybody know where this bit is?  Please let us know.
On the HP28, there is a single bit that turns the LED on, modulated and all;
we hope that there is a correponding bit on the HP48.