I found tutorial about connecting HD44780 display to Raspberry Pi.
In this tutorial there is no contrast potentiometer. Vo is connected to ground.
Tutorial author says:
In order to control the contrast you can adjust the voltage presented to Pin 3. This must be between 0 and 5V. I tied this pin to ground.
Is this common and correct way to use this display?
I never seen that before (Vo connected to GND).