Ruby Serial Library for 4x20 LCD (NHD-0420D3Z-NSW-BBW)

lcd.rb

# RUBY LIBRARY FOR SERIAL COMM RS-323 TO 4X20
# LCD COMPATIBLE WITH THE NEW HAVEN DISPLAY COMMANDS
#
# LCD MODEL# NHD-0420D3Z-NSW-BBW
#
# SPEC SHEET LOCATED:
# http://www.newhavendisplay.com/specs/NHD-0420D3Z-NSW-BBW.pdf
#
# HOOK UP PIN 1 TO TX ON RASBERRY PI
#         PIN 2 TO GND
#         PIN 3 TO 5V
#
# *********************EXAMPLE USAGE***************************
#
# lcd=Display.new(path_to_serial, baudrate) #initializes lcd
# lcd.print("Hello World", 1) #Prints hello world on line 1
#
# *************************************************************

require 'serialport'

class Display
    CMD = 254.chr
    CMD_POS = 69.chr
    ROW_1=0.chr
    ROW_2=64.chr
    ROW_3=20.chr
    ROW_4=84.chr

    HOME = 70.chr
    OFF = 66.chr
    ON = 65.chr
    BLINK_OFF = 76.chr
    LEFT = 73.chr
    RIGHT = 74.chr
    CLEAR = 81.chr


    def initialize (serial_path='/dev/ttyAMA0', baudrate=9600)
        serial_path, baudrate = serial_path.to_s, baudrate.to_i
        #OPEN UP SERIAL PORT
        @display = SerialPort.new serial_path, baudrate
        sleep(0.1)
        #TURN OFF CURSOR
        cmd(BLINK_OFF)
        sleep(0.01)
    end

    def cmd(command)
        @display.write(CMD)
        @display.write(command)
        sleep(0.01)
    end

    def clear
        cmd(CLEAR)
    end

    def off
        cmd(CLEAR)
        cmd(OFF)
    end

    def on
        cmd(ON)
    end

    def write(command)
        @display.write(command)
    end

# ALIGN OPTIONS 1=CENTER, 2= LEFT, 3=RIGHT
    def print(text, line=1, align=1)
        clear_line(line)
        text=text.to_s
        posLine(line)
        if text.length >= 21
            extra_text=text.length-20
            text_array=*(0..extra_text)
            @display.write(text[0,20])

            text_array.each do |it|
                posLine(line)
                @display.write(text[it, 20])
                sleep(0.15)
            end
            sleep(0.5)
            text_array.reverse.each do |it|
                posLine(line)
                @display.write(text[it, 20])
                sleep(0.1)
            end

        else
            padding=20-text.length
            case align
                when 1 #CENTER ALIGN
                    padding = padding/2
                    while padding >= 1
                        text=" " << text
                        padding-=1
                    end
                # DON'T NEED TO MAKE CHANGES FOR LEFT ALIGN
                when 3 #RIGHT ALIGN
                    while padding >= 1
                        text=" " << text
                        padding -= 1
                    end
            end
            @display.write(text)
        end
    end

    def posLine(line)
        cmd(CMD_POS)
        case line
            when 1
                @display.write(ROW_1)
            when 2
                @display.write(ROW_2)
            when 3
                @display.write(ROW_3)
            when 4
                @display.write(ROW_4)
        end
        sleep(0.01)
    end

    def posCursor(pos)
        pos=pos.chr
        cmd(pos)
    end

    def clear_line(line)
        posLine(line)
        @display.write("                    ")
        posLine(line)
    end

    LINE_1 = *(0..19)
    LINE_2 = *(64..83)
    LINE_3 = *(20..39)
    LINE_4 = *(84..103)

    LINE_1_R = LINE_1.reverse
    LINE_2_R = LINE_2.reverse
    LINE_3_R = LINE_3.reverse
    LINE_4_R = LINE_4.reverse

    #TO-DO ADD SCROLLING TEXT

end