LCD module

[metoo25]

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.

 

[Nigel Goodwin]

Look up 4 bit mode and 8 bit mode.

 

[Visitor]

The LCD is a character LCD. These typically display 2 lines of 16 characters.

This type of display can (usually) use either 8 data bits or 4. Four-bit mode is used to cut down on the number of port pins required.

Pins 15 & 16 are used for the LCD backlight. Some displays have a backlight, others don't. Quick tip – the backlight uses LEDs. Some displays have the required current-limiting resistor built in, some do not.

 

[gophert]

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.

Pins 7-10 can be connected so you can transfer all 8-bits (ascii character or LCD command) in one parallel clock cycle. By leaving them disconnected, you can only transfer 4 bits at a time and it needs two clock cycles for each character or command code. It is just a trade off of how many pins would be needed to control the display vs efficiency of the code. Most people want the extra 4 I/O pins on the microcontroller for other things. But if you have plenty of free pins, go for it.