Arduino Tutorial - LCD

About LCD 16x2

Pinout

LCD has up to 16 pins. In the most common uses, we do NOT use all pins.

With the support of LiquidCrystal library, we even can use LCD WITHOUT knowing the meaning of these pins. However, if you are curious or want to know in-depth, let's see these pins and their functionality:

• GND pin: needs to be connected to GND (0V).
• VCC pin: the power supply for the LCD, needs to be connected to VCC (5V).
• Vo (LCD Contrast) pin: controls the contrast and brightness of the LCD, can be connected to 5V (the highest contrast and brightness), or connected to a potentiometer (to adjust to the contrast and brightness)
• RS (Register Select) pin: There are two kinds of data that need to send to LCD: command (to control LCD) and data. These two are sent on the same data bus. RS pin tells the LCD whether the data on the data bus is the commands or the data.
• If we want to send the command to control LCD, we need to set RS pin to LOW (like set the cursor to a specific location, clear the display ...).
• If we want to send the data to display on LCD, we need to set RS pin to HIGH.
• R/W (Read/Write) pin: is to select READ mode or WRITE mode.
• If we want to read data from LCD, this pin needs to be set to HIGH.
• If we want to send data to LCD, this pin needs to be set to LOW. Since we’re just using this LCD as an OUTPUT device, we’re going to tie this pin LOW.
• EN (Enable) pin: is used to enable the LCD. HIGH to enable the LCD, LOW to disable the LCD.
• D0-D7 (Data Bus) pins: carries data and command between Arduino and LCD. There are two modes to send data: 4-bit mode and 8-bit mode.
• A-K (Anode & Cathode) pins: are used to power the LCD backlight. A pin needs to be connected to VCC. K pin needs to be connected to GND.

4-bit mode and 8-bit mode

• 8-bit mode: 8 bits of a byte are sent at the same time in pin D0 to D7.
• 4-bit mode: 8 bits of a byte is sent two times, each time 4 bits in pin D4 to D7.

8-bit mode is faster than the 4-bit mode, but use more pins than 4-bit mode. The mode selection is performed at the initialization process by sending a command to LCD.

This tutorial uses 4-bit mode, which is the most common-used.

In this mode, LCD's pins:

• 6 pins (RS, EN, D4, D5, D6, and D7) are connected to Arduino's pin.
• 4 pins (D0, D1, D2, and D3) are NOT connected.
• 6 remaining pins are connected to GND/VCC or potentiometer.

LCD pin table in 4-bit mode

LCD PIN	CONNECTED TO
01	GND	GND
02	VCC	5V
03	Vo	5V or potentiometer's pin
04	RS	An Arduino's pin
05	R/W	GND
06	EN	An Arduino's pin
07	D0	NOT connected
08	D1	NOT connected
09	D2	NOT connected
10	D3	NOT connected
11	D4	An Arduino's pin
12	D5	An Arduino's pin
13	D6	An Arduino's pin
14	D7	An Arduino's pin
15	A	5V
16	K	GND

LCD Coordinate

LCD 16x2 includes 16 columns and 2 rows. the conlums and rows are indexed from 0.

How It Works

This section is the in-depth knowledge. DON'T worry if you don't understand. Ignore this section if it overloads you, and come back in another day. Keep reading the next sections.

The process of sending data (to be displayed) to LCD:

1. Arduino sets RS pin to HIGH (to select data register)
2. Arduino writes data to D4 → D7 pins (data bus).
3. LCD receives data on the data bus.
4. LCD stores the received data in the data resistor since the RS pin is HIGH. Then, LCD displays the data on the screen

The process of sending command (to control) to LCD (e.g, blink LCD, set the cursor to a specific location, clear the display ...):

1. Arduino sets RS pin to LOW (to select command register)
2. Arduino writes command to D4 → D7 pins (data bus).
3. LCD receives data on the data bus.
4. LCD stores the received data in the command resistor since the RS pin is LOW. Then, LCD takes action based on the value of the command.

Arduino - LCD

Controlling LCD is a quite complicated task. Fortunately, thanks to the LiquidCrystal library, this library simplifies the process of controlling LCD for you so you don't need to know the low-level instructions. You just need to connect Arduino to LCD and use the functions of the library. The using LCD is a piece of cake.