HP-48GX cards other than RM/ROM?

[Jeff_Birt]

I dug out my HP-48s to play with and got to wondering if there were every any other types of expansion cards made for the GX other than RAM/ROM. The Port 2 connector has some signals related to the LCD and I watched a video at lunch today of HHC 2018 that talked about the 50G LCD projector connector which insinuated that the 'something' might be done with these signals on the 48.

After spending some time searching the interwebs I have not found any such device or project. Perhaps the physical constraints of creating such a card made using the relatively simple, and external, serial port connection a more attractive option.