WalkerWiki - wiki.alanwalker.uk

  #!/usr/bin/python
  #--------------------------------------
  #  LCD Test Script
  #
  
  #--------------------------------------
  
  # The wiring for the LCD is as follows:
  # 1 : GND
  # 2 : 5V
  # 3 : Contrast (0-5V)*          -   Sets the LCD Contrast
  # 4 : RS (Register Select)      -   GPIO pin 26 - Physical pin 37
  # 5 : R/W (Read Write)          -   GROUND THIS PIN
  # 6 : Enable or Strobe          -   GPIO pin 19 - Physical pin 35
  # 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                -   GPIO pin 13 - Physical pin 33
  # 12: Data Bit 5                -   GPIO pin 06 - Physical pin 31
  # 13: Data Bit 6                -   GPIO pin 05 - Physical pin 29
  # 14: Data Bit 7                -   GPIO pin 11 - Physical pin 23
  # 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
  
  
  # Define some device constants
  LCD_WIDTH = 40    # Maximum characters per line
  LCD_CHR = True
  LCD_CMD = False
  
  # Do I need to change line 2 address for 40 char display?
  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 = 0.0005
  E_DELAY = 0.0005
  
  def main():
    # Main program block
    
    GPIO.setwarnings(False)
    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
  
  
    # Initialise display
    lcd_init()
  
    while True:
  
      # Send some test
      lcd_string("Rasbperry Pi",LCD_LINE_1)
      lcd_string("40x2 LCD Test",LCD_LINE_2)
  
      time.sleep(3) # 3 second delay
  
      # Send some text
      lcd_string("Another Example :)",LCD_LINE_1)
      lcd_string("Now do your own",LCD_LINE_2)
  
      time.sleep(3)
  
  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 = 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
    lcd_toggle_enable()
  
    # 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
    lcd_toggle_enable()
  
  def lcd_toggle_enable():
    # Toggle enable
    time.sleep(E_DELAY)
    GPIO.output(LCD_E, True)
    time.sleep(E_PULSE)
    GPIO.output(LCD_E, False)
    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__':
  
    try:
      main()
    except KeyboardInterrupt:
      pass
    finally:
      lcd_byte(0x01, LCD_CMD)
      lcd_string("Goodbye!",LCD_LINE_1)
      GPIO.cleanup()