Adafruit_CharLCD.py

#!/usr/bin/python

#
# based on code from lrvick and LiquidCrystal
# lrvic - https://github.com/lrvick/raspi-hd44780/blob/master/hd44780.py
# LiquidCrystal - https://github.com/arduino/Arduino/blob/master/libraries/LiquidCrystal/LiquidCrystal.cpp
#

from time import sleep

class Adafruit_CharLCD:

    # commands
    LCD_CLEARDISPLAY 		= 0x01
    LCD_RETURNHOME 		= 0x02
    LCD_ENTRYMODESET 		= 0x04
    LCD_DISPLAYCONTROL 		= 0x08
    LCD_CURSORSHIFT 		= 0x10
    LCD_FUNCTIONSET 		= 0x20
    LCD_SETCGRAMADDR 		= 0x40
    LCD_SETDDRAMADDR 		= 0x80

    # flags for display entry mode
    LCD_ENTRYRIGHT 		= 0x00
    LCD_ENTRYLEFT 		= 0x02
    LCD_ENTRYSHIFTINCREMENT 	= 0x01
    LCD_ENTRYSHIFTDECREMENT 	= 0x00

    # flags for display on/off control
    LCD_DISPLAYON 		= 0x04
    LCD_DISPLAYOFF 		= 0x00
    LCD_CURSORON 		= 0x02
    LCD_CURSOROFF 		= 0x00
    LCD_BLINKON 		= 0x01
    LCD_BLINKOFF 		= 0x00

    # flags for display/cursor shift
    LCD_DISPLAYMOVE 		= 0x08
    LCD_CURSORMOVE 		= 0x00

    # flags for display/cursor shift
    LCD_DISPLAYMOVE 		= 0x08
    LCD_CURSORMOVE 		= 0x00
    LCD_MOVERIGHT 		= 0x04
    LCD_MOVELEFT 		= 0x00

    # flags for function set
    LCD_8BITMODE 		= 0x10
    LCD_4BITMODE 		= 0x00
    LCD_2LINE 			= 0x08
    LCD_1LINE 			= 0x00
    LCD_5x10DOTS 		= 0x04
    LCD_5x8DOTS 		= 0x00



    def __init__(self, pin_rs=25, pin_e=24, pins_db=[23, 17, 21, 22], GPIO = None):
	# Emulate the old behavior of using RPi.GPIO if we haven't been given
	# an explicit GPIO interface to use
	if not GPIO:
	    import RPi.GPIO as GPIO
   	self.GPIO = GPIO
        self.pin_rs = pin_rs
        self.pin_e = pin_e
        self.pins_db = pins_db

        self.GPIO.setmode(GPIO.BCM)
        self.GPIO.setup(self.pin_e, GPIO.OUT)
        self.GPIO.setup(self.pin_rs, GPIO.OUT)

        for pin in self.pins_db:
            self.GPIO.setup(pin, GPIO.OUT)

	self.write4bits(0x33) # initialization
	self.write4bits(0x32) # initialization
	self.write4bits(0x28) # 2 line 5x7 matrix
	self.write4bits(0x0C) # turn cursor off 0x0E to enable cursor
	self.write4bits(0x06) # shift cursor right

	self.displaycontrol = self.LCD_DISPLAYON | self.LCD_CURSOROFF | self.LCD_BLINKOFF

	self.displayfunction = self.LCD_4BITMODE | self.LCD_1LINE | self.LCD_5x8DOTS
	self.displayfunction |= self.LCD_2LINE

	""" Initialize to default text direction (for romance languages) """
	self.displaymode =  self.LCD_ENTRYLEFT | self.LCD_ENTRYSHIFTDECREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode) #  set the entry mode

        self.clear()


    def begin(self, cols, lines):

	if (lines > 1):
		self.numlines = lines
    		self.displayfunction |= self.LCD_2LINE
		self.currline = 0


    def home(self):

	self.write4bits(self.LCD_RETURNHOME) # set cursor position to zero
	self.delayMicroseconds(3000) # this command takes a long time!
	

    def clear(self):

	self.write4bits(self.LCD_CLEARDISPLAY) # command to clear display
	self.delayMicroseconds(3000)	# 3000 microsecond sleep, clearing the display takes a long time


    def setCursor(self, col, row):

	self.row_offsets = [ 0x00, 0x40, 0x14, 0x54 ]

	if ( row > self.numlines ): 
		row = self.numlines - 1 # we count rows starting w/0

	self.write4bits(self.LCD_SETDDRAMADDR | (col + self.row_offsets[row]))


    def noDisplay(self): 
	""" Turn the display off (quickly) """

	self.displaycontrol &= ~self.LCD_DISPLAYON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def display(self):
	""" Turn the display on (quickly) """

	self.displaycontrol |= self.LCD_DISPLAYON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noCursor(self):
	""" Turns the underline cursor on/off """

	self.displaycontrol &= ~self.LCD_CURSORON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def cursor(self):
	""" Cursor On """

	self.displaycontrol |= self.LCD_CURSORON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noBlink(self):
	""" Turn on and off the blinking cursor """

	self.displaycontrol &= ~self.LCD_BLINKON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noBlink(self):
	""" Turn on and off the blinking cursor """

	self.displaycontrol &= ~self.LCD_BLINKON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def DisplayLeft(self):
	""" These commands scroll the display without changing the RAM """

	self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVELEFT)


    def scrollDisplayRight(self):
	""" These commands scroll the display without changing the RAM """

	self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVERIGHT);


    def leftToRight(self):
	""" This is for text that flows Left to Right """

	self.displaymode |= self.LCD_ENTRYLEFT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode);


    def rightToLeft(self):
	""" This is for text that flows Right to Left """
	self.displaymode &= ~self.LCD_ENTRYLEFT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def autoscroll(self):
	""" This will 'right justify' text from the cursor """

	self.displaymode |= self.LCD_ENTRYSHIFTINCREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def noAutoscroll(self): 
	""" This will 'left justify' text from the cursor """

	self.displaymode &= ~self.LCD_ENTRYSHIFTINCREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def write4bits(self, bits, char_mode=False):
        """ Send command to LCD """

	self.delayMicroseconds(1000) # 1000 microsecond sleep

        bits=bin(bits)[2:].zfill(8)

        self.GPIO.output(self.pin_rs, char_mode)

        for pin in self.pins_db:
            self.GPIO.output(pin, False)

        for i in range(4):
            if bits[i] == "1":
                self.GPIO.output(self.pins_db[::-1][i], True)

	self.pulseEnable()

        for pin in self.pins_db:
            self.GPIO.output(pin, False)

        for i in range(4,8):
            if bits[i] == "1":
                self.GPIO.output(self.pins_db[::-1][i-4], True)

	self.pulseEnable()


    def delayMicroseconds(self, microseconds):
	seconds = microseconds / float(1000000)	# divide microseconds by 1 million for seconds
	sleep(seconds)


    def pulseEnable(self):
	self.GPIO.output(self.pin_e, False)
	self.delayMicroseconds(1)		# 1 microsecond pause - enable pulse must be > 450ns 
	self.GPIO.output(self.pin_e, True)
	self.delayMicroseconds(1)		# 1 microsecond pause - enable pulse must be > 450ns 
	self.GPIO.output(self.pin_e, False)
	self.delayMicroseconds(1)		# commands need > 37us to settle


    def message(self, text):
        """ Send string to LCD. Newline wraps to second line"""

        for char in text:
            if char == '\n':
                self.write4bits(0xC0) # next line
            else:
                self.write4bits(ord(char),True)


if __name__ == '__main__':

    lcd = Adafruit_CharLCD()

    lcd.clear()
    lcd.message("  Adafruit 16x2\n  Standard LCD")