rpi_charlcd.py

# -*- coding: utf-8 -*-
#
# Source: https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code
#
# Written by Limor Fried, Kevin Townsend and Mikey Sklar for Adafruit
# Industries. BSD license, all text above must be included in any
# redistribution
#
# 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
#
# Modified by Danilo Bargen (https://github.com/dbrgn/)


from time import sleep


class CharLCD(object):

    # 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
            GPIO.setmode(GPIO.BCM)

        self.GPIO = GPIO
        self.pin_rs = pin_rs
        self.pin_e = pin_e
        self.pins_db = pins_db

        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.delay_microseconds(3000)  # this command takes a long time!

    def clear(self):
        self.write4bits(self.LCD_CLEARDISPLAY)  # command to clear display
        self.delay_microseconds(3000)  # 3s sleep, clearing the display takes a long time

    def set_cursor(self, col, row):
        self.row_offsets = [0x00, 0x40, 0x14, 0x54]
        if row > self.numlines:
            row = self.numlines - 1  # we count rows starting with 0
        self.write4bits(self.LCD_SETDDRAMADDR | (col + self.row_offsets[row]))

    def no_display(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 no_cursor(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 no_blink(self):
        """ Turn on and off the blinking cursor """
        self.displaycontrol &= ~self.LCD_BLINKON
        self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

    def scroll_Left(self):
        """ These commands scroll the display without changing the RAM """
        self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVELEFT)

    def scroll_right(self):
        """ These commands scroll the display without changing the RAM """
        self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVERIGHT)

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

    def right_to_left(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 no_autoscroll(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.delay_microseconds(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.pulse_enable()

        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.pulse_enable()

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

    def pulse_enable(self):
        self.GPIO.output(self.pin_e, False)
        self.delay_microseconds(1)  # 1 microsecond pause - enable pulse must be > 450ns
        self.GPIO.output(self.pin_e, True)
        self.delay_microseconds(1)  # 1 microsecond pause - enable pulse must be > 450ns
        self.GPIO.output(self.pin_e, False)
        self.delay_microseconds(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 = CharLCD()

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