lcd.py

#!/usr/bin/python
 import RPi.GPIO as GPIO
import time


# 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             - NOT USED
# 8 : Data Bit 1             - NOT USED
# 9 : Data Bit 2             - NOT USED
# 10: Data Bit 3             - NOT USED
# 11: Data Bit 4
# 12: Data Bit 5
# 13: Data Bit 6
# 14: Data Bit 7
# 15: LCD Backlight +5V**
# 16: LCD Backlight GND


class lcd:
    def __init__(self):
        """ Default constructor """
        # Define GPIO to LCD mapping
        self.LCD_RS = 7
        self.LCD_E  = 8
        self.LCD_D4 = 25
        self.LCD_D5 = 24
        self.LCD_D6 = 23
        self.LCD_D7 = 18

        # Define some device constants
        self.LCD_WIDTH = 16    # Maximum characters per line
        self.LCD_CHR = True
        self.LCD_CMD = False
        
        self.LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
        self.LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line

        # Timing constants
        self.E_PULSE = 0.0005
        self.E_DELAY = 0.0005

        # Initialise GPIO for lcd
        self.gpio_init()

        # Initialise lcd
        self.lcd_init()

    def gpio_init(self):
        """ Initialise GPIO for LCD """
        GPIO.setwarnings(False)
        GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
        GPIO.setup(self.LCD_E, GPIO.OUT)  # E
        GPIO.setup(self.LCD_RS, GPIO.OUT) # RS
        GPIO.setup(self.LCD_D4, GPIO.OUT) # DB4
        GPIO.setup(self.LCD_D5, GPIO.OUT) # DB5
        GPIO.setup(self.LCD_D6, GPIO.OUT) # DB6
        GPIO.setup(self.LCD_D7, GPIO.OUT) # DB7

    def gpio_clearup(self):
        """ Clean up GPIO for LCD """
        GPIO.cleanup()

    def lcd_init(self):
        """ Initialise LCD display """
        self.lcd_byte(0x33, self.LCD_CMD) # 110011 Initialise
        self.lcd_byte(0x32, self.LCD_CMD) # 110010 Initialise
        self.lcd_byte(0x06, self.LCD_CMD) # 000110 Cursor move direction
        self.lcd_byte(0x0C, self.LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
        self.lcd_byte(0x28, self.LCD_CMD) # 101000 Data length, number of lines, font size
        self.lcd_byte(0x01, self.LCD_CMD) # 000001 Clear display
        time.sleep(E_DELAY)
     
    def lcd_byte(self, bits, mode):
        """ Send bytes directly to GPIO pins """
        # bits = data
        # mode = True  for character
        #        False for command
        GPIO.output(self.LCD_RS, mode) # RS

        # High bits
        GPIO.output(self.LCD_D4, False)
        GPIO.output(self.LCD_D5, False)
        GPIO.output(self.LCD_D6, False)
        GPIO.output(self.LCD_D7, False)
        if bits&0x10==0x10:
        GPIO.output(self.LCD_D4, True)
        if bits&0x20==0x20:
        GPIO.output(self.LCD_D5, True)
        if bits&0x40==0x40:
        GPIO.output(self.LCD_D6, True)
        if bits&0x80==0x80:
        GPIO.output(self.LCD_D7, True)

        # Toggle 'Enable' pin
        self.lcd_toggle_enable()

        # Low bits
        GPIO.output(self.LCD_D4, False)
        GPIO.output(self.LCD_D5, False)
        GPIO.output(self.LCD_D6, False)
        GPIO.output(self.LCD_D7, False)
        if bits&0x01==0x01:
        GPIO.output(self.LCD_D4, True)
        if bits&0x02==0x02:
        GPIO.output(self.LCD_D5, True)
        if bits&0x04==0x04:
        GPIO.output(self.LCD_D6, True)
        if bits&0x08==0x08:
        GPIO.output(self.LCD_D7, True)

        # Toggle 'Enable' pin
        self.lcd_toggle_enable()

    def lcd_toggle_enable(self):
        # Toggle enable
        time.sleep(self.E_DELAY)
        GPIO.output(self.LCD_E, True)
        time.sleep(self.E_PULSE)
        GPIO.output(self.LCD_E, False)
        time.sleep(self.E_DELAY)

    def lcd_string(self, message,line):
        # Send string to display
        message = message.ljust(self.LCD_WIDTH," ")

        self.lcd_byte(line, self.LCD_CMD)

        for i in range(self.LCD_WIDTH):
          lcd_byte(ord(message[i]), self.LCD_CHR)

if __name__ == '__main__':
    display = lcd()
    try:
        # Main program
        while True:
            # Send some test
            lcd_string("Rasbperry Pi",LCD_LINE_1)
            lcd_string("16x2 LCD Test",LCD_LINE_2)

            time.sleep(3) # 3 second delay

            # Send some text
            lcd_string("1234567890123456",LCD_LINE_1)
            lcd_string("abcdefghijklmnop",LCD_LINE_2)

            time.sleep(3) # 3 second delay

            # Send some text
            lcd_string("RaspberryPi-spy",LCD_LINE_1)
            lcd_string(".co.uk",LCD_LINE_2)

            time.sleep(3)

            # Send some text
            lcd_string("Follow me on",LCD_LINE_1)
            lcd_string("Twitter @RPiSpy",LCD_LINE_2)

            time.sleep(3)
    except KeyboardInterrupt:
        pass
    finally:
        display.gpio_clearup()
        display.lcd_byte(0x01, display.LCD_CMD)
        display.lcd_string("Goodbye!", display.LCD_LINE_1)