#!/usr/bin/python
    #
    # HD44780 LCD Test Script for
    # Raspberry Pi
    #
    # Author : Matt Hawkins
    # Site   : http://www.raspberrypi-spy.co.uk
    # 
    # Date   : 03/08/2012
    #
    
    # 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
    
    #import
    import RPi.GPIO as GPIO
    import time
    
    # Define GPIO to LCD mapping
    LCD_RS = 26
    LCD_E  = 19
    LCD_D4 = 13 
    LCD_D5 = 6
    LCD_D6 = 5
    LCD_D7 = 11
    LED_ON = 15
    
    # Define some device constants
    LCD_WIDTH = 16    # Maximum characters per line
    LCD_CHR = True
    LCD_CMD = False
    
    LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
    LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line 
    
    # Timing constants
    E_PULSE = 0.00005
    E_DELAY = 0.00005
    
    def main():
      # Main program block
    
      # Initialise display
      lcd_init()
    
      # Toggle backlight on-off-on
      GPIO.output(LED_ON, True)
      time.sleep(1)
      GPIO.output(LED_ON, False)
      time.sleep(1)
      GPIO.output(LED_ON, True)
      time.sleep(1)
    
      # Send some centred test
      lcd_byte(LCD_LINE_1, LCD_CMD)
      lcd_string("Rasbperry Pi",2)
      lcd_byte(LCD_LINE_2, LCD_CMD)
      lcd_string("Model B",2)
    
      time.sleep(3) # 3 second delay
    
      # Send some left justified text
      lcd_byte(LCD_LINE_1, LCD_CMD)
      lcd_string("1234567890123456",1)
      lcd_byte(LCD_LINE_2, LCD_CMD)
      lcd_string("abcdefghijklmnop",1)
    
      time.sleep(3) # 3 second delay
    
      # Send some right justified text
      lcd_byte(LCD_LINE_1, LCD_CMD)
      lcd_string("Raspberrypi-spy",3)
      lcd_byte(LCD_LINE_2, LCD_CMD)
      lcd_string(".co.uk",3)
    
      time.sleep(30)
    
      # Turn off backlight
      GPIO.output(LED_ON, False)
    
    def lcd_init():
      GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
      GPIO.setup(LCD_E, GPIO.OUT)  # E
      GPIO.setup(LCD_RS, GPIO.OUT) # RS
      GPIO.setup(LCD_D4, GPIO.OUT) # DB4
      GPIO.setup(LCD_D5, GPIO.OUT) # DB5
      GPIO.setup(LCD_D6, GPIO.OUT) # DB6
      GPIO.setup(LCD_D7, GPIO.OUT) # DB7
      GPIO.setup(LED_ON, GPIO.OUT) # Backlight enable  
      # Initialise display
      lcd_byte(0x33,LCD_CMD)
      lcd_byte(0x32,LCD_CMD)
      lcd_byte(0x28,LCD_CMD)
      lcd_byte(0x0C,LCD_CMD)  
      lcd_byte(0x06,LCD_CMD)
      lcd_byte(0x01,LCD_CMD)  
    
    def lcd_string(message,style):
      # Send string to display
      # style=1 Left justified
      # style=2 Centred
      # style=3 Right justified
    
      if style==1:
        message = message.ljust(LCD_WIDTH," ")  
      elif style==2:
        message = message.center(LCD_WIDTH," ")
      elif style==3:
        message = message.rjust(LCD_WIDTH," ")
    
      for i in range(LCD_WIDTH):
        lcd_byte(ord(message[i]),LCD_CHR)
    
    def lcd_byte(bits, mode):
      # Send byte to data pins
      # bits = data
      # mode = True  for character
      #        False for command
    
      GPIO.output(LCD_RS, mode) # RS
    
      # High bits
      GPIO.output(LCD_D4, False)
      GPIO.output(LCD_D5, False)
      GPIO.output(LCD_D6, False)
      GPIO.output(LCD_D7, False)
      if bits&0x10==0x10:
        GPIO.output(LCD_D4, True)
      if bits&0x20==0x20:
        GPIO.output(LCD_D5, True)
      if bits&0x40==0x40:
        GPIO.output(LCD_D6, True)
      if bits&0x80==0x80:
        GPIO.output(LCD_D7, True)
    
      # Toggle 'Enable' pin
      time.sleep(E_DELAY)    
      GPIO.output(LCD_E, True)  
      time.sleep(E_PULSE)
      GPIO.output(LCD_E, False)  
      time.sleep(E_DELAY)      
    
      # Low bits
      GPIO.output(LCD_D4, False)
      GPIO.output(LCD_D5, False)
      GPIO.output(LCD_D6, False)
      GPIO.output(LCD_D7, False)
      if bits&0x01==0x01:
        GPIO.output(LCD_D4, True)
      if bits&0x02==0x02:
        GPIO.output(LCD_D5, True)
      if bits&0x04==0x04:
        GPIO.output(LCD_D6, True)
      if bits&0x08==0x08:
        GPIO.output(LCD_D7, True)
    
      # Toggle 'Enable' pin
      time.sleep(E_DELAY)    
      GPIO.output(LCD_E, True)  
      time.sleep(E_PULSE)
      GPIO.output(LCD_E, False)  
      time.sleep(E_DELAY)   
    
    if __name__ == '__main__':
      main()