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2. VL is used to adjust the contrast. It connected in series the potentiometer is not greater than
a 5KΩ. This experimental used one 1KΩ of resistor to set contrast. There are high potential
connection and low potential connection. It connected in series 1KΩ resistance then
connected to GND.
Basic Operation
Read status
Input
RS=L, R/W=H, E=H
Output
D0~D7=status word
Write command
Input
RS=L, R/W=L,
D0~D7=command code, E=
high pulse
Output
none
Read data
Input
RS=H, R/W=H, E=H
Output
D0~D7=data
Write data
Input
RS=H, R/W=L, D0~D7=data,
E= high pulse
Output
none
output of the sketch on a 2x16 LCD
The LCDs have a parallel interface, meaning that the microcontroller has to manipulate several
interface pins at once to control the display. The interface consists of the following pins:
A register select (RS) pin that controls where in the LCD's memory you're writing data to. You can
select either the data register, which holds what goes on the screen, or an instruction register,
which is where the LCD's controller looks for instructions on what to do next.
A Read/Write (R/W) pin that selects reading mode or writing mode
An Enable pin that enables writing to the registers
8 data pins (D0 -D7). The states of these pins (high or low) are the bits that you're writing to a
register when you write, or the values you're reading when you read.
There's also a display constrast pin (Vo), power supply pins (+5V and Gnd) and LED Backlight
(Bklt+ and BKlt-) pins that you can use to power the LCD, control the display contrast, and turn on
and off the LED backlight, respectively.
The process of controlling the display involves putting the data that form the image of what you
want to display into the data registers, then putting instructions in the instruction register. The
LiquidCrystal Library simplifies this for you so you don't need to know the low-level instructions.
The Hitachi-compatible LCDs can be controlled in two modes: 4-bit or 8-bit. The 4-bit mode
requires seven I/O pins from the Arduino, while the 8-bit mode requires 11 pins. For displaying
text on the screen, you can do most everything in 4-bit mode, so example shows how to control a
2x16 LCD in 4-bit mode.
Circuit
To wire your LCD screen to your Arduino, connect the following pins:
LCD RS pin to digital pin 12
LCD Enable pin to digital pin 11
LCD D4 pin to digital pin 5
LCD D5 pin to digital pin 4
LCD D6 pin to digital pin 3
LCD D7 pin to digital pin 2