making HP39GS Serial Cable (RS-232)

[ilkka777]

(05-02-2019 09:14 PM)rprosperi Wrote:  You are asking the SERIAL port and not the USB port, right? (it has both)

Assuming you mean the serial port, see notes on this page:

https://commerce.hpcalc.org/serialcable.php

This is about the 50g, but the serial port in the 39gs is the same h/w as the 50g.

Also, more details here:

https://www.allenwan.com/hpcalcserialcable/

This post had good set of links, some of those you mentioned too:
https://www.hpmuseum.org/forum/thread-75...rial+cable

Still too little information around the web or im not finding any.

So far I gathered
* Voltage levels all positive (as claimed), 3.3V and Vcc from battery around 5-6V
* USB connector is same as Minolta DiMAGE S-304/404/414
* bits are sent like 8N2 as far as I understand?: no parity, two stop bits, 8 bit data, one start bit
-> technical interfacing guide explains how to create HP objects, like lists or matrices *)
* idle state between byte transmissions (stop bits)
* not sure how end of transmission is signaled?
* still unsure how handshake is done when transmitting serial (from menu send to another HP39GS thru serial)

*) downloaded some HP objects, in hex editor there can be easily seen the header, file name and HP Object with prolog & epilogue (please notice it uses 4bit nibbles, LSB (or should I say "least significant nibble") first, so it is harder to read when two nibbles of different fields are located in one same byte)