#!/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()