LCD (Liquid Crystal Display):
LCD screen is an electronic
display module and find a wide range of applications. A 16x2 LCD display is
very basic module and is very commonly used in various devices and circuits.
These modules are preferred over seven segment and other multi
segment LED's. The reasons being: LCDs are economical; easily
programmable; have no limitation of displaying special & even custom
character (unlike in seven segments), animation and so on. A 16x2
LCD means it can display 16 characters per line and there are 2 such
lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD
has two registers, namely, Command and Data.
The command register stores the command instructions given to the LCD. A command
is an instruction given to LCD to do a predefined task like initializing it,
clearing its screen, setting the cursor position, controlling display etc. The
data register stores the data to be displayed on the LCD. The data is the ASCII
value of the character to be displayed on the LCD. Click to learn more about
internal structure of a LCD.
Block Diagram of LCD:
LCD stands for liquid crystal display. They come in
many sizes 8x1 , 8x2 ,10x2, 16x1 , 16x2 , 16x4 , 20x2 , 20x4 ,24x2 , 30x2 ,
32x2 , 40x2 etc . Many multinational companies
like Philips Hitachi Panasonic make their own special kind
of lcd's to be used in their products. All the lcd’s performs the same
functions (display characters numbers special characters ASCII characters
etc).Their programming is also same and they all have same 14 pins (0-13)
or 16 pins (0 to 15).
The wiring for the LCD is as follows:
1 : GND
2 : 5V
3 : Contrast (0-5V)
4 : RS (Register Select)
5 : R/W (Read Write) - GROUND THIS
PIN
6 : Enable or Strobe
7 : Data Bit 0
8 : Data Bit 1
9 : Data Bit 2
10: Data Bit 3
11: Data Bit 4
12: Data Bit 5
13: Data Bit 6
14: Data Bit 7
15: LCD Backlight +5V
16: LCD Backlight GND
1) Write a program to
Display “ABCDEFG” on the Lcd using 8 Bit Mode:
Now ready to write code to Display on LCD.
Turn on your Raspberry Pi and Open the terminal window.
Create a new text file “lcd1.py” by typing
the following:
Sudo nano lcd1.py
After that write following code to the
Text editer page:
import RPi.GPIO as IO
import time
import sys
IO.setmode (IO.BCM #board usage
gpio pin , bcm usasge pin mnumber IO.setup(6,IO.OUT)
# initialize all 10 GPIO Pins as a
outputs
IO.setup(22,IO.OUT)
IO.setup(21,IO.OUT)
IO.setup(20,IO.OUT)
IO.setup(16,IO.OUT)
IO.setup(12,IO.OUT)
IO.setup(25,IO.OUT)
IO.setup(24,IO.OUT)
IO.setup(23,IO.OUT)
IO.setup(18,IO.OUT)
def send_a_command (command):
pin=command
PORT(pin);
IO.output(6,0)
#put
rs=0; means lcd work in command mode
IO.output(22,1)
# first put the value of en pin is 1 then
time.sleep(0.05)
# after some delay put zero
IO.output(22,0)
pin=0
PORT(pin);
def send_a_character
(character):
pin=character
PORT(pin);
IO.output(6,1)
# put rs=1; means lcd work in data mode
IO.output(22,1) )
# first put the value of en pin is 1 then
time.sleep(0.05)
# after some delay put zero
IO.output(22,0)
pin=0
PORT(pin);
def PORT(pin):
# assig PIN by taking
PORT value
if(pin&0x01
== 0x01):
IO.output(21,1) # if bit0 of
8bit 'pin' is true, pull PIN21 high
else:
IO.output(21,0) # if bit0 of
8bit 'pin' is false, pull PIN21 low
if(pin&0x02
== 0x02):
IO.output(20,1) # if bit1 of 8bit
'pin' is true, pull PIN20 high
else:
IO.output(20,0) # if bit1 of 8bit 'pin' is
false, pull PIN20 low
if(pin&0x04
== 0x04):
IO.output(16,1) # if bit2 of 8bit 'pin' is true, pull PIN16 high
else:
IO.output(16,0) # if bit2 of 8bit 'pin' is false, pull
PIN16 low
if(pin&0x08
== 0x08):
IO.output(12,1) # if bit3 of 8bit 'pin' is true, pull PIN12 high
else:
IO.output(12,0) # if bit3 of 8bit 'pin' is false, pull PIN12 low
if(pin&0x10 == 0x10):
IO.output(25,1) # if bit4 of 8bit 'pin' is true, pull PIN25 high
else:
IO.output(25,0) # if bit4 of 8bit 'pin' is false, pull PIN25 low
if(pin&0x20
== 0x20):
IO.output(24,1) # if bit5 of 8bit 'pin' is true, pull PIN24 high
else:
IO.output(24,0) # if bit5 of 8bit 'pin' is false, pull PIN24 low
if(pin&0x40
== 0x40):
IO.output(23,1) # if bit6 of 8bit 'pin' is true, pull PIN23 high
else:
IO.output(23,0) # if bit6 of 8bit 'pin' is false, pull PIN23 low
if(pin&0x80
== 0x80):
IO.output(18,1) # if bit7 of 8bit 'pin' is true, pull PIN18 high
else:
IO.output(18,0) # if bit7 of 8bit 'pin' is false, pull
PIN18 low
while 1:
send_a_command(0x01);
# CLEAR DISPLAY SCREEN
send_a_command(0x38);
# INITIALIZE 16*2 line LCD
send_a_command(0x0E);
# DISPLAY ON CURSOR BLINKING
send_a_character(0x41);
# ASCII code for 'A'
send_a_character(0x42);
# ASCII code for 'B'
send_a_character(0x43);
# ASCII code for 'C'
send_a_character(0x44);
# ASCII code for 'D'
send_a_character(0x45);
# ASCII code for 'E'
send_a_character(0x46);
# ASCII code for 'F'
send_a_character(0x47);
# ASCII code for 'G'
time.sleep(1)
After writing the code we checked it, save
and exit the text editor with
“Ctrl + x” then “y” then “enter”.
To Running this Code Type:
sudo python lcd1.py
then
You will see the ABCDEFG is Display on the
LCD.
Circuit
Diagram:
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