Path: utzoo!attcan!uunet!cs.utexas.edu!samsung!brutus.cs.uiuc.edu!psuvax1!psuvm!cunyvm!byuvax!yoda!rhelps
From: rhelps@yoda.byu.edu
Newsgroups: comp.sys.handhelds
Subject: hp48 serial cable
Message-ID: <97rhelps@yoda.byu.edu>
Date: 28 Mar 90 00:41:49 GMT
Lines: 38

>Could someone who has hacked up a serial cable for their 48 send me
>  a pinout for the hp's serial port?  I'd like to do it, too -
>  a pinout for the hp's serial port?  I'd like to do it, too -
>  parts it will cost to make one.

Here it is.  But first a disclaimer.  Hewlett Packard will not support
home-made connections and niether will I.  If you try this you accept
ALL risks of possible damage

Pin numbering (unofficial).  Lay the calculator on the table and look into the
port.  Number the pins 1-4 from left to right.  Pin number 4 is closest
to the IR leds.

9 pin AT style RS232 connector.       HP connector
     2  (Rx)                              2
     3  (Tx)                              3
     5  (Gnd)                             4
     -----                                1 (Chassis ground ??)
I also shorted pins 1, 6, 7, and 8 on the nine pin connector.  I'm not sure
if this is strictly necessary but it works.

The most difficult job is finding suitable connectors for the HP plug.
They are neither standard size nor standard spacing.  I found some
slip-on connections at my local electronic supply store that
work well.  I had to squeeze them a little with pliers to get a tight fit
and I used Heat-shrink tubing to insulate them and provide them with rigidity.
Whatever you use BE GENTLE.  If you make a mistake you will have an expensive
repair job on your hands - not to mention the trauma of being separated
from your calculator for awhile.  One consolation though, The owners manual at
the back implies that if you accidentally short some pins no damage will
result.

The Kermit transfer protocol works well.  I use Procomm which is available
as shareware on many bulletin boards.  Just use standard upload and
download procedures and select Kermit as the protocol.

This cable works with my own programs as well as those on the HP bulletin
board.  I had a lot of trouble initially and thought it was the cable
but it turned out to be the XMODEM corrupted files discussed earlier on this
network.