Olimex LCD16x2

Nice stuff by the way.

Things to know:

Power

As acknowledged by the schematics, the controller is using 3.3V, while the display is using 5V. So if you're doing your own wiring (like using a Nano, Teensy or whatever), you need to connect both the 3.3V and 5V power pins.

Reset

The reset pin can't be overlooked ! If you're not connecting it, you risk some strange behaviour, because the MCU and he display might go out of sync. If you're using an Arduino Uno, it will just work because the reset is wired. If you're doing your own wiring (for example on the Nano), you should wire the display reset to the Nano reset. On Teensy, things are more complicated, because the reset isn't accessible or propagated.