making HP39GS Serial Cable (RS-232)

[rprosperi]

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/