Hello everyone, today we are going to learn how to use a liquid crystal display. I use a Hitachi HD44780 LCD, a 16×2 display (16 columns and 2 rows, 32 characters in total), that is cheap and easy to get.
The display has 16 pins: 2 for the power, 2 for the backlight, 1 for contrast adjustement, 3 control lines and 8 for writing data. However, in this post I am going to transfer data in 4bit: so I only use 4 of these last pins. Let’s analyze the pins in detail.
Below, a table with every pin’s name and function:
|4||RS||Register select signal|
|7||D0||Data bus line|
|8||D1||Data bus line|
|9||D2||Data bus line|
|10||D3||Data bus line|
|11||D4||Data bus line|
|12||D5||Data bus line|
|13||D6||Data bus line|
|14||D7||Data bus line|
|15||BL+||+5V for blacklight|
|16||BL-||GND for blacklight|
Here a more accurated descriptions of certain pins:
- Pin 3 (V0) is usually connected to a potentiometer, so that the user can apply a voltage variation (from 0 to +5V): in this way, he can adjust the LCD contrast.
- Pin 4 (RS) is used to control in which lcd memory you want to write. You can select the data register, that hold data which will be printed on the screen, or the instructions register, that is where the LCD look for istructions on what to do.
- Pin 7 to 14 (D0-D7) are control lines that send or receive data to or from LCD’s registers.
For further information, look up the datasheet.
Because of the number of used pins, there will be a lot of wires, but don’t worry, it’s quite simple. Here’s the scheme: