Path: utzoo!attcan!uunet!snorkelwacker!mit-eddie!uw-beaver!ubc-cs!fs1!fs1.ee.ubc.ca!jthornto
From: jthornto@fs1.ee.ubc.ca (THORNTON JOHAN A)
Newsgroups: comp.sys.handhelds
Subject: Re: HP48SX: pin assignements and dumb question
Message-ID: <1302@fs1.ee.ubc.ca>
Date: 7 Jul 90 02:31:36 GMT
References: <1990Jul6.115520.10510@gorgo.ifi.unizh.ch>
Sender: root@fs1.ee.ubc.ca
Reply-To: jthornto@fs1.ee.ubc.ca (THORNTON JOHAN A)
Organization: Dept. of Electrical Engineering University of B.C.
Lines: 43


Here are the pinouts for the 48SX serial port:



                  4 3 2 1
     /------------|-|-|-|----\
    |   48SX                  |    Pin   Function    Standard RS232 pin eqv.
    |   ___________________   |                       (25 pin connector)
    |  |                   |  |     1  Chassis Ground       1
    |  | 4:         "THIS" |  |     2  Transmit Data        2
    |  | 3:           "IS" |  |     3  Receive Data         3
    |  | 2:          "THE" |  |     4  Signal Ground        7
    |  | 1:       "SCREEN" |  |
    |   -------------------   |
    |                         |
    | [A] [B] [C] [D] [E] [F] |
    | MTH PRG CST VAR  ^  NXT |
    |     .  .  .  .  .  .    |

If you're making a cable, just make a standard null modem cable.
(reverse RX and TX)

      48SX pin           RS232 pin

   CHG   1  - - - - - - - -  1  CHG     Chassis ground does not
                                        actually have to be connected.
    TX   2  ------\ /------  2  TX
                   X
    RX   3  ------/ \------  3  RX

   GND   4  ---------------  7  GND


I have a problem with my cable: the PC won't receive data from the HP.
Anybody have any ideas?  The loopbacks work on both sides.  I think it
may be a problem with signal levels - the HP supposedly doesn't use
standard RS232 voltage levels.  A line driver could be installed to raise
the voltage.  Netters?

.sig
>Johan Thornton
>UBC Electrical Engineering