------------------------------------------------------------------------
--  LCD driver
--  Author : David Li, Eric Cheun, Felicia Cheng, Wilson Kwan
--  Date   : 2000 winter
--  Architecture : Display
--  Description: to initialize the LCD and wait for the user
--  to input the characters.
------------------------------------------------------------------------

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
library work;
use work.CDMA_pkg.all;

entity lcddriver is
	port(
        clock, clk_en: in std_logic;
        resetn		: in std_logic;

		-- input from outside such as a keypad
		message		: in std_logic_vector (2 downto 0); 

		-- lcd register select signal
		lcd_select	: out std_logic; 
		lcd_data	: out std_logic_vector(7 downto 0);
		lcd_rw		: out std_logic;
		lcd_enable	: out std_logic;

		-- detect if there is any incoming message
		enable		: in std_logic
	);
end lcddriver;

-- Architecture Description

architecture Display of lcddriver is

	TYPE STATE_TYPE IS (initial, display, entrymode, clear, waiting, verify,
		putchar, homecursor);
	SIGNAL state,next_state: STATE_TYPE;

	-- Clear screen.
	constant CLR:   std_logic_vector(7 downto 0) := "00000001";
	-- Display ON, with cursor.
	constant DON:   std_logic_vector(7 downto 0) := "00001110";
	-- Set Entry Mode to increment cursor automatically after each character
	-- is displayed.
	constant SEM:   std_logic_vector(7 downto 0) := "00000110";
	-- Home cursor
	constant HOME:  std_logic_vector(7 downto 0) := "00000010";
	-- Function set for 8-bit data transfer and 2-line display
	constant SET:   std_logic_vector(7 downto 0) := "00111000";

	-- The numbers and symbols
	constant zero:	std_logic_vector(7 downto 0) := "00110000";
	constant one:	std_logic_vector(7 downto 0) := "00110001";
	constant two:	std_logic_vector(7 downto 0) := "00110010";
	constant three:	std_logic_vector(7 downto 0) := "00110011";
	constant four:	std_logic_vector(7 downto 0) := "00110100";
	constant five:	std_logic_vector(7 downto 0) := "00110101";
	constant six:	std_logic_vector(7 downto 0) := "00110110";
	constant seven:	std_logic_vector(7 downto 0) := "00110111";
	constant eight:	std_logic_vector(7 downto 0) := "00111000";
	constant nine:	std_logic_vector(7 downto 0) := "00111001";
	constant star:	std_logic_vector(7 downto 0) := "00101010";
	constant pound:	std_logic_vector(7 downto 0) := "00100011";

	-- Some potentially useful puctuation.
	constant SP:    std_logic_vector(7 downto 0) := "00100000"; -- Space

	constant big_delay: integer :=14;
	constant small_delay: integer :=2;
	constant reg_setup: integer :=1;
	constant lastposition: integer:=16;

begin

	lcd_rw<='0';
	process (clock,resetn,enable)

		variable position: integer range 0 to lastposition;
		variable count: integer range 0 to big_delay;

	begin

		wait until clock'event and clock = '1';

		IF resetn = '0' THEN -- test resetn
			state<=initial;
			position:=0;
			count:=0;
		elsif clk_en = '1' then
			case state is
				WHEN initial => -- to set the function
					if count=reg_setup then
						lcd_enable<='1';
					else
						lcd_enable<='0';
					end if;
					lcd_data<=SET;
					lcd_select<='0';
					if count=small_delay then
						state<=display;
						count:=0;
					else
						count:=count+1;
					end if;

				WHEN display => -- to set display on
					if count=reg_setup then
						lcd_enable<='1';
					else
						lcd_enable<='0';
					end if;
					lcd_data<=DON;
					lcd_select<='0';
					if count=small_delay then
						state<=entrymode;
						count:=0;
					else
						count:=count+1;
					end if;

				WHEN entrymode => 
					-- to set entry mode, increment after each character
					-- is displayed
					if count=reg_setup then
						lcd_enable<='1';
					else
						lcd_enable<='0';
					end if;
					lcd_data<=SEM;
					lcd_select<='0';
					if count=small_delay then
						state<=clear;
						count:=0;
					else
						count:=count+1;
					end if;

				WHEN clear => -- clear the screen
					if count=reg_setup then
						lcd_enable<='1';
					else
						lcd_enable<='0';
					end if;
					lcd_data<=CLR;
					lcd_select<='0';
					if count=big_delay then
						state<=waiting;
						count:=0;
					else
						count:=count+1;
					end if;

				when waiting => -- wait for input
					if enable='0' then
						state<=verify;
					end if;

				when verify =>
					if enable='1' then
						if position=lastposition then
							state<=homecursor;
							position:=0;
						else
							state<=putchar;
						end if;
					end if;

				when putchar=> -- display the character on the LCD
					if count=reg_setup then
						lcd_enable<='1';
					else
						lcd_enable<='0';
					end if;
					case message is
						when "000" => lcd_data<=zero;
						when "001" => lcd_data<=one;
						when "010" => lcd_data<=two;
						when "011" => lcd_data<=three;
						when "100" => lcd_data<=four;
						when "101" => lcd_data<=five;
						when "110" => lcd_data<=six;
						when "111" => lcd_data<=seven;
						--when "1000" => lcd_data<=eight;
						--when "1001" => lcd_data<=nine;
						--when "1010" => lcd_data<=star;
						--when "1011" => lcd_data<=pound;
						when others => lcd_data<=SP;
					end case;
					lcd_select<='1';
					if count=small_delay then
						state<=waiting;
						position:=position+1;
						count:=0;
					else
						count:=count+1;
					end if;

				when homecursor=>
					if count=reg_setup then
						lcd_enable<='1';
					else
						lcd_enable<='0';
					end if;
					lcd_data<=HOME;
					lcd_select<='0';
					if count=big_delay then
						state<=putchar;
						count:=0;
					else
						count:=count+1;
					end if;

			end case;
		end if;
	end process;

end Display;