Xref: utzoo sci.electronics:18820 comp.sys.handhelds:6403
Newsgroups: sci.electronics,comp.sys.handhelds
Path: utzoo!utgpu!watserv1!watdragon!dahlia!aehammond
From: aehammond@dahlia.uwaterloo.ca (nq)
Subject: HP28S serial interface
Message-ID: <1991Mar27.024649.17275@watdragon.waterloo.edu>
Keywords: hardware mods, HP28S
Sender: daemon@watdragon.waterloo.edu (Owner of Many System Processes)
Organization: University of Waterloo
Date: Wed, 27 Mar 1991 02:46:49 GMT
Lines: 28

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I am looking for some pointers to information on the HP28S scientific
calculator's hardware. Specifically, I wish to give it serial input
capabilities.

I've seen the reviews on HP28COM, but would like to do this myself.

Has anybody     1) done this
                2) know of someone who has/a book which describes it
                3) got any opinions on what is a good method

My thoughts on the subject were to maybe bridge on of the keys
and use an assembly program to read it.

How about the IO ports -- is the IR port write-only? (ie IN/OUT instructions)

While I have it open, is it feasible to add a 32K ram chip?

Any and all info, advice etc would be appreciated. (It was hard enough to 
figure out how to open the case).

Thanks for reading.

Don.

email DABOWMAN@SYSTEMS.WATSTAR.WATERLOO.EDU || 
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