            Connecting a modem to your HP48 or HP49G calculator

by E.Carta

Version 3.00


Warning: This is *NOT* a Hewlett-Packard official page. I assume no
responsibility about any damage you could get by following these
schematics.

0. Index.

   * 0. Index.
   * 1. Introduction.
   * 2. Pinout assignment (read carefully!)
        o 2.1. HP48-4pin Connector
        o 2.2. HP49G-10pin Connector
        o 2.3. DB9 Connector (RS-232)
        o 2.4. DB25 Connector (RS-232)
   * 3. Building the cable
        o 3.1. Project #1: HP48 - Building the whole cable
        o 3.2. Project #2: HP49 - Building the whole cable
        o 3.3. Project #3: HP48 and HP49 - Building the adapter for cable
          F1897-66000
        o 3.4. Project #4: HP48 - Building the adapter for cable
          F1015-80002
        o 3.5. Project #5: HP49 - Building the adapter for cable
          F1015-80002
   * 4. Testing the cable
        o 4.1. Testing the HP48-Modem Cable
        o 4.2. Testing the HP49-Modem Cable
   * 5. Getting the software
   * 6. Connecting your HP to a remore PC or a remote calculator
        o 6.1 Upload/Download files using Kermit protocol
             + 6.1.1. Download a file from a remote PC
             + 6.1.2. Upload a file to a remote PC
        o 6.2. Connect two HP calculators through the telephone line
   * 7. Solve connection problems
        o 7.1. "Connection doesn't work. Am I using a wrong modem?"
        o 7.2. "I connect my HP to the modem, then type ATI0, but nothing
          happens"
        o 7.3. "I get modem prompt, but it doesn't dial the number"
        o 7.4. "I can connect a remote server, but then I get no answer on
          terminal"
        o 7.5. "Files appear truncated after upload/download operations"
        o 7.6. Other problems -OR- problem persists
   * 8. Related documents
   * 9. Obtaining the last version of this document
   * 10. Contacting the author of this document

---------------------------------------------------------------------------

1. Introduction.

These pages explain how connecting any standard-modem to your HP48 or HP49
calculator.

Following instructions below, you'll be able to join BBS services, to chat
and to upload or download files, both on remote PCs and even on a remote HP
calculator !

You'll learn to build the connection cable and to get all the FREE required
software .

You need the computer only the first time, to transfer terminal programs to
your HP calculator. Then, you won't need other devices than your HP, the
cable and the modem.

Notice: you won't be able to send/receive fax, neither to access Internet
directly.

   * Please read carefully the pinout assignment section.
   * Be sure to check your cable before using it!

2. Pinout assignment.

   * I assume the calculator as a DTE, so RX means data TO calculator,
     while TX means data FROM calculator.
   * The MODEM is obviously a DCE, so TX and RX are always referred to the
     DTE (the calculator): TX means "Transmitted from calculator".
   * Pinout numbering is different (mirrored) in Male and Female
     connectors. So be careful!!!
   * Please read carefully the schematics below; for further information,
     refer to: http://www.freeweb.org/computer/enrico/hpcables.htm

2.1. HP48-4pin Connector

   * Connectors are seen in front view, with the HP logo on their top.
   * HP48 back view. I assume pin #4 is THE NEAREST TO THE IR-LEDS:

           LCD SCREEN
+--------------------'--------+
|  +-----------------------+  |
|  |    ....         OO    |  |
\  |    1234      (IR-LEDS)|  /
 \_|_______________________|_/

 PINOUT NUMBERING:

             HP48-4pin-M                        HP48-4pin-F

            [ 1  2  3  4 ]                     [ 4  3  2  1 ]

 PINOUT DESCRIPTION:
  1. SHIELD
  2. TX (TRANSMITTED = CALCULATOR OUTPUT)
  3. RX (RECEIVED = CALCULATOR INPUT)
  4. GND

2.2. HP49G-10pin Connector

   * Connectors are seen in front view, with the HP logo on their top.
   * The male connector in the upper-side of the calculator is seen in
     front view (LCD screen on the top) in this way:

            LCD SCREEN
/|-----------------------------|\
|    +---^-----------------+    |
|____| .....  <pin 1 to 5  |____|
|    | .....  <pin 6 to 10 |    |
|    \---------------------/    |
\-------------------------------/

 PINOUT NUMBERING:

             HP49G-10pin-M                       HP49G-10pin-F

          +-------/-\-------+                 +-------/-\-------+
          |  1  2  3  4  5  |                 |  5  4  3  2  1  |
          |  6  7  8  9  10 |                 | 10  9  8  7  6  |
          \-----------------/                 \-----------------/

 PINOUT DESCRIPTION:
  6. SHIELD
  7. TX (TRANSMITTED = CALCULATOR OUTPUT)
  8. RX (RECEIVED = CALCULATOR INPUT)
  9. GND

2.3. DB9 Connector (RS-232).


                 DB9-M                             DB9-F

          -------------------               -------------------
          \  1  2  3  4  5  /               \  5  4  3  2  1  /
           \   6  7  8  9  /                 \   9  8  7  6  /
            ---------------                   ---------------

 PINOUT DESCRIPTION:
  2. TX (MODEM INPUT = DATA FROM CALCULATOR)
  3. RX (MODEM OUTPUT = DATA TO CALCULATOR)
  4. DTR
  5. GND
  6. DSR
  7. RTS

2.4. DB25 Connector (RS-232).


                 DB25-M                              DB25-F

      ---------------------------          ---------------------------
      \  1  2  3 [..] 11 12 13  /          \  13 12 11 [..] 3  2  1  /
       \  14 15 [..] 23 24 25  /            \  25 24 23 [..] 15 14  /
        -----------------------              -----------------------

 PINOUT DESCRIPTION:
  2. RX (MODEM OUTPUT = DATA TO CALCULATOR)
  3. TX (MODEM INPUT = DATA FROM CALCULATOR)
  4. RTS
  6. DSR
  7. GND
 20. DTR


3. Building the cable.

The cable you need should connect the modem and the HP calculator directly
together. No PC is needed.

The HP calculators don't support RTS and DTR pins, required by most of the
modems. So, you have to connect them to the DSR pin, whose signal is
originated by the modem itself, at the end of the modem cable. Simply short
pins 4, 6, 20 (on modem DB25-M connector) or pins 4, 6, 7 (if your modem
uses a DB9-M).

A cable like this is not available, so you have to build it by yourself.

You have two ways to do it:

  1. Build the whole cable (see Project #1 or #2);
  2. Build an adapter between the PC-Link Cable and the modem (see Project
     #3, #4 or #5).

To know the pinout numbering used by me, please refer to the previous
section.

3.1. Project #1: HP48 - Building the whole cable.

What you need: a DB25-M connector (or DB9-M if your modem uses it), some
wires and a 4pin-F connector to plug into the HP48 port. Note that in the
calculator you only need to connect three pins (since SHIELD is not
mandatory); so you can get it by recycling the 3 (or 4)-pin female
connectors used into old computer mainboards (for example: CD-ROM cable,
HDD power-connector for portable computers, etc.).

Ask to a computer shop or, better, to a surplus-dealer in order to find a
computer connector that fits your HP48 port.

Building the cable: Solder the 4-pin-F connector to the DB25-M (or to the
DB9-M if your modem uses it).

Schematic:

     HP48-4-F            DB25-M             DB9-M
 SHIELD (1)-+-------------(SHIELD)
            +--------------------------------(SHIELD)
      TX 2-----+---------->2
               +----------------------------->3
      RX 3<-+--------------3
            +<--------------------------------2
     GND 4-----+-----------7
               +------------------------------5
                         4,6,20             4,6,7   <--SHUNTED

            Testing the cable                       Back to index

3.2. Project #2: HP49 - Building the whole cable.

What you need: a DB25-M connector (or DB9-M if your modem uses it), some
wires and a 10pin-F connector to plug into the HP49G port. Note that in the
calculator you only need to connect three pins (since SHIELD is not
mandatory), all in the bottom-row (pin 7 to 9); so you can get it by
recycling the 3 (or 4)-pin female connector used into old computer
mainboards (for example: HDD-led, turbo-led, keylock-switch, etc.), or get
it from some broken hardware (for example, an old mouse).

Ask to a computer shop or, better, to a surplus-dealer in order to find a
computer connector that fits the pins (6),7,8 and 9 in your HP49G.

Building the cable: Solder the 3-pin-F connector to the DB25-M (or to the
DB9-M if your modem uses it).

Schematic:

    HP49-10-F            DB25-M             DB9-M
 SHIELD (6)-+-------------(SHIELD)
            +--------------------------------(SHIELD)
      TX 7-----+---------->2
               +----------------------------->3
      RX 8<-+--------------3
            +<--------------------------------2
     GND 9-----+-----------7
               +------------------------------5
                         4,6,20             4,6,7   <--SHUNTED

            Testing the cable                       Back to index

3.3. Project #3: HP48 and HP49 - Building the adapter for cable
F1897-66000.

What you need: some wires, a DB9-M and DB25-M connector (or two DB9-M
connectors if your modem uses it) and the HP serial PC-Link cable. In this
section I'm referring to newer models of cable (like F1897, F1207B or
8120-6736), that can be used on both HP48 and HP49G. For older cables (like
F1015-80002) see section 3.4 or 3.5. The HP38 has the same pinout as the
HP49G, so you can use also a HP38 PC-Link.

NEVER (**NEVER**) plug this cable directly into your DB9 modem. You could
damage it!

To use this cable you need to build a DB9-DB25 adapter (or DB9-DB9 if your
modem uses a DB9 connector).

Using the adapter.

   * Build the adapter (see schematic below);
   * Plug the DB9-F termination of your serial cable to the DB9-M connector
     of the adapter and connect all in this way:

+-----------------+                      +-----------+   +---------+
|  HP CALCULATOR  |<-----------------><--|  ADAPTER  |-->|  MODEM  |
+-----------------+      PC-LINK         +-----------+   +---------+

Schematic of the adapter:

     (TO PC-LINK)       (TO MODEM)         (TO MODEM)
      DB9-M              DB25-M             DB9-M
   (SHIELD)-+-------------(SHIELD)
            +--------------------------------(SHIELD)
      TX 2-----+---------->2
               +----------------------------->3
      RX 3<-+--------------3
            +<--------------------------------2
     GND 5-----+-----------7
               +------------------------------5
                         4,6,20             4,6,7   <--SHUNTED

            Testing the cable                       Back to index

3.4. Project #4: HP48 - Building the adapter for cable F1015-80002.

What you need: some wires, a DB9-M and DB25-M connector (or two DB9-M
connectors if your modem uses it) and the HP serial PC-Link cable. In this
section I'm referring to older models of cable (like F1015-80002). For
newer cables (like F1897, F1207B or 8120-6736) see section 3.3. For using
this cable with the HP49G see next section.

NEVER (**NEVER**) plug this cable directly into your DB9 modem. You could
damage it!

To use this cable you need to build a DB9-DB25 adapter (or DB9-DB9 if your
modem uses a DB9 connector).

Using the adapter.

   * Build the adapter (see schematic below);
   * Plug the DB9-F termination of your serial cable to the DB9-M connector
     of the adapter and connect all in this way:

+----------+                      +-----------+   +---------+
|   HP48   |<-----------------><--|  ADAPTER  |-->|  MODEM  |
+----------+      PC-LINK         +-----------+   +---------+

Schematic of the adapter:

     (TO PC-LINK)       (TO MODEM)         (TO MODEM)
      DB9-M              DB25-M             DB9-M
   (SHIELD)-+-------------(SHIELD)
            +--------------------------------(SHIELD)
      TX 2-----+---------->2
               +----------------------------->3
      RX 3<-+--------------3
            +<--------------------------------2
     GND 5-----+-----------7
               +------------------------------5
                         4,6,20             4,6,7   <--SHUNTED

            Testing the cable                       Back to index

3.5. Project #5: HP49 - Building the adapter for cable F1015-80002.

What you need: some wires, a DB9-M and DB25-M connector (or two DB9-M
connectors if your modem uses it) and the HP serial PC-Link cable. In this
section I'm referring to older models of cable (like F1015-80002). For
newer cables (like F1897, F1207B or 8120-6736) see section 3.3. For using
this cable with the HP48 see previous section.

NEVER (**NEVER**) plug this cable directly into your DB9 modem. You could
damage it!

WARNING: This cable cannot be used as HP49G PC-Link. But can be used as
HP49G-Modem cable by building the adapter below.

To use this cable you need to build a DB9-DB25 adapter (or DB9-DB9 if your
modem uses a DB9 connector).

Using the adapter.

   * Build the adapter (see schematic below);
   * Plug the DB9-F termination of your serial cable to the DB9-M connector
     of the adapter and connect all in this way:

+-----------+                      +-----------+   +---------+
|   HP49G   |<-----------------><--|  ADAPTER  |-->|  MODEM  |
+-----------+      PC-LINK         +-----------+   +---------+

Schematic of the adapter:

     (TO PC-LINK)       (TO MODEM)         (TO MODEM)
      DB9-M              DB25-M             DB9-M
   (SHIELD)-+-------------(SHIELD)
            +--------------------------------(SHIELD)
      TX 8-----+---------->2
               +----------------------------->3
      RX 7<-+--------------3
            +<--------------------------------2
     GND 9-----+-----------7
               +------------------------------5
                         4,6,20             4,6,7   <--SHUNTED

            Testing the cable                       Back to index

4. Testing the cable.

Before using your new cable for the first time, check it!

4.1. Testing the HP48-Modem Cable.

No matter what method you've followed. The cable you use MUST have:

   * A HP48 4-pin connector on one side, and a DM25-M or DB9-M on the
     other;
   * A schematic like this (check with the ohmmeter):

     HP48-4-F            DB25-M             DB9-M
 SHIELD (1)-+-------------(SHIELD)
            +--------------------------------(SHIELD)
      TX 2-----+---------->2
               +----------------------------->3
      RX 3<-+--------------3
            +<--------------------------------2
     GND 4-----+-----------7
               +------------------------------5
                         4,6,20             4,6,7   <--SHUNTED

   * If you use pin #1 (on the HP48-4pin side), connect it to the shield.
     Otherwise, don't connect it (SHIELD is not mandatory).
   * Pin 4, 6, 20 on DB25 (or 4, 6, 7 if your modem uses a DB9 connector)
     are connected togheter because HP calculators don't support DTR and
     RTS signals.
   * All the pins should be insulated each from the others and each from
     the SHIELD (except pin #1). Check with the ohmmeter!.
   * DON'T USE cables with a different schematic. To fix the problem, read
     carefully the pinout assignment of the connectors and the schematic of
     the cable you are building.

4.2. Testing the HP49-Modem Cable.

No matter what method you've followed. The cable you use MUST have:

   * A HP49 10-pin connector on one side, and a DM25-M or DB9-M on the
     other;
   * A schematic like this (check with the ohmmeter):

    HP49-10-F            DB25-M             DB9-M
 SHIELD (6)-+-------------(SHIELD)
            +--------------------------------(SHIELD)
      TX 7-----+---------->2
               +----------------------------->3
      RX 8<-+--------------3
            +<--------------------------------2
     GND 9-----+-----------7
               +------------------------------5
                         4,6,20             4,6,7   <--SHUNTED

   * If you use pin #6 (on the HP49-10pin side), connect it to the shield.
     Otherwise, don't connect it (SHIELD is not mandatory).
   * Pin 4, 6, 20 on DB25 (or 4, 6, 7 if your modem uses a DB9 connector)
     are connected togheter because HP calculators don't support DTR and
     RTS signals.
   * All the pins should be insulated each from the others and each from
     the SHIELD (except pin #6). Check with the ohmmeter!.
   * DON'T USE cables with a different schematic. To fix the problem, read
     carefully the pinout assignment of the connectors and the schematic of
     the cable you are building.

5. Getting the software.

You need a terminal program to have your HP calculator to talk with the
modem.

Most of these programs are FREE and can be found in hpcalc archive:

* HP48 Terminal Emulation Programs:
http://www.hpcalc.org/utils/comms/terminal/
* HP49 Terminal Emulation Programs: http://www.hpcalc.org/hp49/utils/comms/

Running these programs, you'll be able to talk directly with your modem.
The same your do when using Telix or HyperTerminal on your PC.

Note that you can get the echo of your chars only if you connect to the
modem!

6. Connecting your HP to a remore PC or a remote calculator.

Run your favorite terminal program on the HP calculator.

To dial a number, simply type ATDTnnn (dial-tone) or ATDPnnn (dial-pulse),
when nnn is the number you have to talk with.

Example: to dial-tone number 555-1234, type ATDT 5551234 when running
terminal.

The welcome-message or login-request will soon appear on the screen.

6.1 Upload/Download files using Kermit protocol.

This is the most interesting feature.

You can download/upload any file from/to remote services, using Kermit
protocol.

Be sure you set binary transfer both in local (HP calculator) and in remote
(PC, or another calculator).

The trick is to start the process on remote device, using terminal program.
Then, quit the terminal program and start the Kermit of your HP to complete
the operation. Keeping the modem offhook during all the time.

Then you can re-start the terminal program and close the remote connection.

Kermit official web page is http://www.columbia.edu/Kermit.

6.1.1. Download a file from a remote PC.

Assuming you have logged-in, are running the terminal program, and the
remote Kermit-server is called KERMIT.

Prompt> KERMIT  ;Start remote Kermit server

Kermit> BIN     ;Set to binary. Also used: SET FILE TYPE BINARY

Kermit> SEND FILENAME  ;Ask to send a remote file called FILENAME

"Kermit is ready to send FILENAME. Please run your local Kermit client..."

Now you have to quit from your terminal program.

From the stack, type

RECV   ;Start local Kermit client

Your Kermit client (built in HP calculator ROM) will download the file in
current directory.

Now, restart your terminal program:

"File FILENAME has been sent successfully."

Kermit> QUIT   ;quit remote Kermit server

Prompt>

6.1.2. Upload a file to a remote PC.

Assuming you have logged-in, are running a terminal program, and the remote
Kermit-client is called KERMIT.

Prompt> KERMIT   ;Start remote Kermit client

Kermit> BIN      ;Set to binary. Also used: SET FILE TYPE BINARY

Kermit> RECEIVE  ;Ask the remote client to wait for a file

"Kermit is ready to receive a file. Please run your local Kermit server..."

Now you have to quit from your terminal program.

From the stack, type

-35 SF  ;set to binary

'FILENAME' SEND  ;ask to send a local file called FILENAME

Your Kermit server (built in HP calculator ROM) will upload the file to the
remote client.

Now, restart your terminal program:

"File FILENAME has been received successfully."

Kermit> QUIT  ;quit remote Kermit client

Prompt>

6.2. Connect two HP calculators through the telephone line.

Connect each HP calculator to a standard modem. Then, run a terminal
program on both calculators.
From client calculator, type:

ATA   ;Set client-side modem in autoanswer-mode

From server calculator, type ATDTnnn (dial-tone) or ATDPnnn (dial-pulse),
when nnn is the phone-number of client calculator.

Client and server calculators will connect to each other.
Now, quit both terminal programs (order is not important) and type, from
the stack:

RECV   ;on the client HP.

'OBJECT' SEND   ;on the server HP.

Be sure both calculators are in binary mode, and Kermit are configured in
the same way.

Client HP calculator will receive the 'OBJECT' from the server calculator.

To hang-up, just type:

ATH0

from the terminal program on both calculators.

7. Solve connection problems.

After having tested the cable, connect it to the modem, and send some
command. For example, ATI0 or ATI3 (get modem status), followed by ENTER.
You should read the modem prompt ("OK") on the terminal screen. Otherwise,
you have a connection problem.

7.1. "Connection doesn't work. Am I using a wrong modem?".

You can use any HAYES-standard modem. I used successfully an old Hayes 2400
and a newer 3COM Voice-Faxmodem V90-56000. A 2400 modem is enough, and,
anyway, 9600bps is the highest speed for the HP serial interface.

7.2. "I connect my HP to the modem, then type ATI0, but nothing happens".

Check the cable, and verify that pins 4,6,20 on DB25 (or 4,6,7 if your
modem uses a DB9) are shunted together.

If you are sure the problem is not in the cable, is probably in the modem.
Please refer to your modem manual, and check the proper init string.

If you would find a init-string that allows a correct connection between
the modem and hp48-terminal, you could save it in the modem NVRAM (see
modem manual, the command is usually &W).

7.3. "I get modem prompt, but it doesn't dial the number".

From the terminal program send a the command:

ATX3  <ENTER>  ;Ignore line-signal.

7.4. "I can connect a remote server, but then I get no answer on terminal".

It could be a problem with the init-string. Disconnect, and send to modem
following AT command:

AT&D0&R1  <ENTER>

then re-try the connection.

7.5. "Files appear truncated after upload/download operations".

It probably depends by the small buffer in HP calculator serial interface.
And because there's no handshake between calculator and the modem.

You could force the modem to transmit data with a lower speed. Send the
command:

AT&Nx

where x is the speed:

   * 1 for 300bps
   * 2 for 1200bps
   * 3 for 2400bps
   * 4 for 4800bps
   * 6 for 9600bps

7.6. Other problems -OR- problem persists.

Contact me and explain your problems.

8. Related documents.

   * Description of some HP38, HP48 and HP49G cables & adapters
     http://www.freeweb.org/computer/enrico/hpcables.htm
   * Building the HP49G serial PC-Link cable:
     http://www.freeweb.org/computer/enrico/cable49g.htm
   * HP48 Documentation files: http://www.hpcalc.org/docs/misc/
   * HP49 Documentation files: http://www.hpcalc.org/hp49/docs/misc/
   * The HP48 and HP49G FAQ: http://www.hpcalc.org
   * Kermit official page: http://www.columbia.edu/Kermit
   * C.Curtis, D.L.Majhor, Modem Connections Bible, Sams, ISBN
     0-672-22446-1

9. Obtaining the last version of this document.

Primary address for this page is:
http://www.freeweb.org/computer/enrico/hp2modem.htm

Secondary address: http://studenti.ing.unipi.it/~s172776/hp2modem.htm

PK-zipped version: (16Kb)
http://www.freeweb.org/computer/enrico/hp2modem.zip

Text-Only version: http://www.freeweb.org/computer/enrico/hp2modem.txt

10. Contacting the author of this document.

Feel free to contact me for any problem or question.

My E-mail addresses are:

   * enrico@ieee.org
   * s172776@studenti.ing.unipi.it

-------------------------

Written by E.Carta, enrico@ieee.org, Telecommunications Engineering Student
at the University of Pisa (Italy).
URL: http://www.freeweb.org/computer/enrico/hp2modem.htm
Last Revised: Mar 01, 2000 - Version 3.00.

