I look at this schematic of the HP48SX:

https://www.hpcalc.org/details/3543

It shows that the screendriver-circuit are two SED1181 serial connectet.

I think that is unusual because the datasheet of the SED1181 claims
that it build together with an SED1191 for a matrix-lcd.

I wonder if it is possible to grab the two data-bit in a microcontroller
and translate it for an oled for a much better readable display.
Did knows the code that generate the LCD-Signal to the output bits?

I still like my old HP48, but the low contrast of the early graphic-lcd,
are very poor by todays standard.

Of course it is now only an idea. :-)

Olaf