HP50g - RS-232 cable

[Claudio L.]

(10-12-2016 03:12 PM)joeres Wrote:  But can you explain to me, why the level shifter can not simply supply with the power from the 50g?

Thank you and best regards,
Joerg

I meant those ready-made circuits you can buy at sparkfun, etc. are wired to take power from the PC side. You'd have to modify them to get power from the calc, I have no idea how easy (or not) could that be as I haven't had one of them in my hands. I think the old MAX232 needs 5V (not sure, as I haven't used it in almost 10 years), I can't recall if the calc supplies 5V or 3.3V on the serial port. That info should be on comp.sys.hp48 if you dig a little.
Powering from the calc was not trivial, I vaguely recall reading discussions at comp.sys.hp48 about problems when the calc powered off.