Ruby Library for Parallax 16 x 2 Serial LCD for Raspberry Pi

lcd.rb

#  LIBRARY FOR CONTROL PARALLAX 16x2 SERIAL LCD DISPLAY ON A RASBERRY PI
#
#              Wiring Diagram
#          PI                   LCD
#        ****************************
#         pin 8 (TX)  ------->  RX
#         pin 6 (GND) ------->  GND
#         pin 2 (5V)  ------->  5V
#
#
#  Datasheet available at:
#  http://www.parallax.com/dl/docs/prod/audiovis/seriallcd-reve.pdf
#
#
#
#
#
#
# *********************************************************************
#                              Example
# *********************************************************************
#  require '/home/pi/lcd'
#
#  lcd = Display.new('/dev/ttyAMA0', 9600)
#  lcd.clear #<-----turn on backlight and clear any text
#
#  # lcd.scroll(text, line and direction option, speed)
#  # text variable accepts any string
#  # line and direction options  1 - Right to left row 1
#  #                            2 - Right to left row 2
#  #                            3 - Left to right row 1
#  #                            4 - Left to right row 2
#  # speed - supplied to delay, smaller number the faster scroll.
#  #         Best results between 0.15 to 0.25

#  lcd.scroll("Your text goes here", 1, 0.2)

require 'serialport'

class Display

    BLINK = 24.chr
    OFF = 18.chr
    ON = 17.chr
    FRAME_OFF = 21.chr
    FRAME_ON = 22.chr
    NEWLINE = 13.chr
    NOTE = 220.chr
    PLAY = 212.chr
    CLEAR = 12.chr
    CURSOR = 22.chr

    def initialize (serial_path, baudrate)
        serial_path, baudrate = serial_path.to_s, baudrate.to_i
    #OPEN UP SERIAL PORT
        @display = SerialPort.new serial_path, baudrate
    #TURN OFF BLINKING CURSOR
        @display.write(BLINK)
    #TURN OFF CURSOR
        @display.write(CURSOR)
    #TURN ON BACKLIGHT
        @display.write(ON)
    end

    def clear
        @display.write(CLEAR)
    end

    def frame_off
        @display.write(FRAME_OFF)
    end

    def frame_on
        @display.write(FRAME_ON)
    end

    def off
        self.clear
        self.scroll("Turning off display...", 1)
        sleep(2)
        @display.write(CLEAR)
        @display.write(OFF)
    end

    def print(text)
        text=text.to_s
        @display.write(text)
    end

    def posCursor(pos)
        pos=pos.chr
        @display.write(pos)
    end

    def wipe(top_bottom, speed)
        self.scroll("                 ", top_bottom, speed)
    end

    def scroll(text, top_bottom, speed)
        top_RtoL=[143,142,141,140,139,138,137,136,135,134,133,132,131,130,129,128]
        top_LtoR=[128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143]
        bottom_RtoL=[163,162,161,160,159,158,157,156,155,154,153,152,151,150,149,148]
        bottom_LtoR=[148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163]
        width=15  #WIDTH OF SCREEN STARTING FROM ZERO
        head = 0

        case top_bottom
            when 1
                lcd_array = top_RtoL
            when 2
                lcd_array = bottom_RtoL
            when 3
                lcd_array = top_LtoR
            when 4
                lcd_array = bottom_LtoR
        end

    # RIGHT TO LEFT SCROLLING
        if top_bottom == 1 || top_bottom == 2
            text=text.to_s << " "
            x=0
            if text.length<16
                text_with_padding=text
    #ADD PADDING TO TEXT TO FILL SCREEN
                while x<17-text_with_padding.length
                    text_with_padding << " "
                end
                length = text_with_padding.length
            else
                text_with_padding=text
                length=text.length
            end
    #SCROLL ALL THE WAY THROUGH THE TEXT
            while head < length-1
                if head >=15
                    pos=15
                else
                    pos=head
                end
                self.posCursor(lcd_array[pos])
                if head > width
                    start_pos=head-pos
                else
                    start_pos=0
                end
                if head>=width
                    chars_to_display=width+1
                else
                    chars_to_display=head+1
                end
                @display.write(text_with_padding[start_pos,chars_to_display])
                sleep(speed)
                head += 1
            end
    #RETURN TEXT TO THE BEGINNING
        end
    #LEFT TO RIGHT SCROLLING
        if top_bottom == 3 || top_bottom == 4
            text=" " << text.to_s << " "
            length=text.length
            while head < length
                self.posCursor(lcd_array[0])
                if head>=width
                    chars_to_display=width
                else
                    chars_to_display=head
                end
                @display.write(text[length-head,chars_to_display+1])
                sleep(speed)
                head += 1
            end
        end
    end

end