Hello, I'm analyzing this project where they are using 3 push buttons, a LCD module, a potentiometer and some leds. I'm wondering why pin 7-10 and 15-16 is not connected to anything on the LCD module? I have tried to look at the datasheet, and I am still a bit uncertain.

Here are the circuit diagram attached.

Thank you in advance.

 

Hi M25,
The LCD is using just the 4 High nibble bits, the data is sent in two 4 Bit bytes, a common way of using the LCD.
Pins 15 are 16 are the LCD backlight LEDs.
E

 

There are two ways of interfacing with an 8-bit parallel LCD.
You can interface in 8-bit mode or in 4-bit mode. Most people choose 4-bit mode because it frees up four GPIO pins.

Some LCD interfaces have 14 pins and others have 16 pins. Usually, pins 15 and 16 are used for back-lighting.

Edit: Eric types faster than I can.