From Donald Papp on Hackaday:
Back when LCD character displays based on the HD44780 controller were the bee’s knees, a way to make them easier to work with came in the form of “backpack” PCBs, which provided an accessible serial interface and superior display handling at the same time. [Barbouri] has updated that idea with a backpack board that mounts to OLED displays using the US2066 display driver, and provides an I2C interface with powerful and convenient high-level functions that make the display simple to use.
On the software side, the backpack uses this I2cCharDisplay driver project which provides functions like cursor control, fading, display shifting, and of course writing characters or strings. While [Barbouri] designed the board specifically to accommodate Newhaven Slim Character OLED displays, it should in theory work with any US2066-based OLED character display. [Barbouri]’s design files for the Slim-OLED Display backpack board are available for download directly from the project page (link is near the bottom), or boards can be purchased directly from OSH Park.