HP41 - RS232 - PC Interfacing


Dear HP41 and PC enthusiasts :

I need detailed information about the wiring between a 9pin PC COM1 serial port and the 25pin port of the HP-IL/RS232 Interface HP82164.

Tony Duell describes a solution for his Linux software tool, but unfortunately his document includes only the wiring between two 25pin connectors.

As I find out some different wiring diagramms exist, describing RS232 inferface connections between 25pin/25pin or 9pin/9pin or 9pin/25pin connections :-(

I am looking for a RS232 solution which works for HP41 and HP71.

Waiting for your help - Christoph Klug


Obviously I use the wiring scheme in my LIF Utilities distribution to link my handhelds to my own PC, which has a DE-9 serial port.

I use a normal PC modem cable -- the same one I use for my modem, actually, plugged into the PC. It has a DE-9 socket on the PC end, a DB25 plug on the 'modem' end, and is wired in the normal way for such cables (I will look up the wirelist if you really can't find the wiring for such a cable). There are no crossovers or the like in the cable.

I then connect that to the 'PC' socket of the adapter I documented in the LIF Utilities distribution, and plug the other end of the adapter into my 82164 with the internal DIP jumper set to the DTE position (this is, IMHO, the only sane way to use the 82164).


Dear Tony,

thanks - that information helps : You use a standart 9pin to 25pin RS232 connection :-)

Best regards - Christoph Klug


Standard pin usage is as follows:

9-pin  desc  dir   25-pin
1 (DCD) I 8
2 RD 1 3
3 TD O 2
4 DTR O 20
5 GND 7
6 DSR I 6
7 RTS O 4
8 CTS I 5
9 (RI) I 22

The "I" and "O" above for "input" and "output" refer to what's connected to the DB-9 end. The DCD and RI are only used for modems, which you're not dealing with right now. All the DB-25 pins are defined except for 9, 10, 18, and 25 which are reserved, but it's rare to see more than the "big 8" actually used. Those are the ones shown above, minus RI. The FSI164A HPIL-RS232 interface converter used the extra pins for more channels. I just got the standard model, so I only have two channels; but there was the option to go up to 8, and they all went through the DB-25. The extra channels only had TD & RD, no handshaking lines.

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