Environment
- Raspberry Pi 3B+
- Raspbian GNU/Linux 9.4
- Python 3
- SunFounder I2C LCD Module Display 16×2
Setup I2C
$ sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Code
#!/usr/bin/python3
import smbus2 as smbus
import time
# Define some device parameters
I2C_ADDR = 0x27 # I2C device address, if any error, change this address to 0x3f
LCD_WIDTH = 16 # Maximum characters per line
# Define some device constants
LCD_CHR = 1 # Mode - Sending data
LCD_CMD = 0 # Mode - Sending command
LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line
LCD_LINE_3 = 0x94 # LCD RAM address for the 3rd line
LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th line
LCD_BACKLIGHT = 0x08 # On
ENABLE = 0b00000100 # Enable bit
# Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005
# Open I2C interface
# bus = smbus.SMBus(0) # Rev 1 Pi uses 0
bus = smbus.SMBus(1) # Rev 2 Pi uses 1
def lcd_init():
# Initialise display
lcd_byte(0x33, LCD_CMD) # 110011 Initialise
lcd_byte(0x32, LCD_CMD) # 110010 Initialise
lcd_byte(0x06, LCD_CMD) # 000110 Cursor move direction
lcd_byte(0x0C, LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
lcd_byte(0x28, LCD_CMD) # 101000 Data length, number of lines, font size
lcd_byte(0x01, LCD_CMD) # 000001 Clear display
time.sleep(E_DELAY)
def lcd_byte(bits, mode):
# Send byte to data pins
# bits = the data
# mode = 1 for data
# 0 for command
bits_high = mode | (bits & 0xF0) | LCD_BACKLIGHT
bits_low = mode | ((bits << 4) & 0xF0) | LCD_BACKLIGHT
# High bits
bus.write_byte(I2C_ADDR, bits_high)
lcd_toggle_enable(bits_high)
# Low bits
bus.write_byte(I2C_ADDR, bits_low)
lcd_toggle_enable(bits_low)
def lcd_toggle_enable(bits):
# Toggle enable
time.sleep(E_DELAY)
bus.write_byte(I2C_ADDR, (bits | ENABLE))
time.sleep(E_PULSE)
bus.write_byte(I2C_ADDR, (bits & ~ENABLE))
time.sleep(E_DELAY)
def lcd_string(message, line):
# Send string to display
message = message.ljust(LCD_WIDTH, " ")
lcd_byte(line, LCD_CMD)
for i in range(LCD_WIDTH):
lcd_byte(ord(message[i]), LCD_CHR)
if __name__ == '__main__':
lcd_init()
while True:
# Send some test
lcd_string("Hello ", LCD_LINE_1)
lcd_string(" World", LCD_LINE_2)
time.sleep(3)
Reference
