Abstract: Hitachi LCD display ( 16x2 ) controlled via I2C, Input is done via single rotating push knob...;-)
You need to find a LCD display that understands 4-bit data, Hitachi HD44780 etc.
As you see, the nibble P0:P4 is used for data, P4 Register select, P5 is the enable, P6 is a LED(!?), and P7 could be Read/Write (pull-upp with 5-10k) or what ever.

For example JAL sources,  you have to dig into the ShipEnvironment project's Zip file. But the PCF8574 is easy to use but fast and expensive...

And the Eagle files is

NB. This PCB you need to make longer to fit behind the display

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