lcddriver.vhd

LCD dispay driver in VHDL

-- EE552 Sign Language Glove Project
--References:
--www.ee.ualberta.ca/~elliott/ee552/studentAppNotes/2000_w/interfacing/lcd_driver/lcddriver.vhd
--and
--www.ee.ualberta.ca/~elliott/ee552/studentAppNotes/1997f/lcd/lcd.html

library ieee;
use ieee.std_logic_1164.all;

library work;
use work.LCD_pkg.all;

entity LCDdriver is 
generic( big_delay: integer := 2000; -- delay needed for slow instructions
		 small_delay: integer :=100; -- delay needed for fasttructions
		 setup_delay: integer := 50  -- initial delay

);
		port(
        clock: in std_logic;
        reset: in std_logic;
        message: in std_logic_vector( LCDdatasize - 1 downto 0 );
        enable: in std_logic;
        lcd_data: out std_logic_vector( LCDdatasize - 1 downto 0 );
        lcd_rs: out std_logic;
        lcd_rw: out std_logic;
        lcd_enable: out std_logic;
        LED1: out std_logic_vector( LEDseg - 1 downto 0 );
        LED2: out std_logic_vector( LEDseg - 1 downto 0 )
		);
      
end entity LCDdriver;

 
-- Architecture Description
 
architecture Display of LCDdriver is
 

type state_type is (initial, display, entrymode, clear, waiting, verify, putchar, homecursor);

signal state: state_type;
signal prev_state: state_type;


begin
        
  process (clock,reset)

    variable position: integer range 0 to lastposition; 
    variable count: integer range 0 to big_delay;
    variable initcount: integer range 0 to big_delay;
  begin
    
    if reset = '0' then     --active low reset

    	  state <=initial;
	      position:=0;
	      count:=0;
		  initcount:=0;
    	  LED1 <= "1000000";
		  LED2 <= "1000000";
    
	elsif clock'event and clock = '1' then  
      case state is
 
       when initial => -- set SET (initalization step)
		  if initcount < big_delay then  --create delay at beginning
			 initcount :=initcount + 1;
		  else
		 
		  if count < setup_delay then
	          lcd_enable <= '1';  -- enable LCD
		  else
			  lcd_enable <= '0';
		  end if;
	
	   	  LED1 <= "1111001";--1
          lcd_data <=SET;  -- send SET instruction
          lcd_rs<='0';  -- instruction mode
		  lcd_rw<='0';

          -- when count = small delay, go onto the next state
          if count = small_delay then 
			prev_state <= initial;
            state<=display;
            count:=0;
          else-- else increment the count 
            count:=count+1;
          end if;
		end if;          
        when display => -- to set DISPLAY (initalization step)
		  if count < setup_delay then
	          lcd_enable <= '1';  -- enable LCD
		  else
			  lcd_enable <= '0';
		  end if;

	      LED1 <= "0100100";--2
          lcd_data<=DON;
          lcd_rs<='0';
		  lcd_rw<='0';
          if count=small_delay then
			prev_state <= display;
            state<=clear;
            count:=0;
          else
            count:=count+1;
          end if;


		when clear => -- clear the screen (initalization step)

		  if count < setup_delay then
	          lcd_enable <= '1';  -- enable LCD
		  else
			  lcd_enable <= '0';
		  end if;

		  LED1 <= "0110000"; --3
          lcd_data<=CLR;
          lcd_rs<='0';
		  lcd_rw<='0';
          if count = big_delay then                         
			if prev_state = homecursor then
				state<=putchar;
			elsif prev_state = display then
	            state<=entrymode;   
			end if;
			prev_state <= clear;
            count:=0; 
          else                          
            count:=count+1;   
          end if;     
     
        when entrymode => -- to set ENTRY MODE (initalization step)
		LED1 <= "0011001";--4

		  if count < setup_delay then
	          lcd_enable <= '1';  -- enable LCD
		  else
			  lcd_enable <= '0';
		  end if;

          lcd_data<=SEM;
          lcd_rs<='0';
		  lcd_rw<='0';
          if count=small_delay then
			prev_state <= entrymode;
            state<=waiting;
            count:=0;
          else
            count:=count+1;
          end if;
                 
        when waiting => -- wait enable to go low (i.e. current input done)
			LED1 <= "0010010";--5
          if enable='1' then
	            state<=verify;
          end if;
            
        when verify =>  -- wait enable to go high (i.e. next input coming)
          -- if recieved an enable (incoming data)
		LED1 <= "0000010";  --6
          if enable='0' then
            -- if end of display is reached, goto state homecursor
            if position=lastposition then
			  prev_state <= verify;
              state<=homecursor;
              position:=0;
            else -- else goto putchar
              state<=putchar;
            end if;
          end if;
            
        when putchar=>  -- display the character on the LCD                    
	   	LED1 <= "0000000";--8

		  if count < setup_delay then
	          lcd_enable <= '1';  -- enable LCD
		  else
			  lcd_enable <= '0';
		  end if;

          lcd_data <= message; --send msg to LCD
          lcd_rs<='1'; -- set to data mode
	      lcd_rw<= '0';
		if count=big_delay then
			prev_state <= putchar;
            state<=waiting; -- go back to waiting when done
            position:=position+1; --increment the position for next char
            count:=0;
          else
            count:=count+1;
          end if;
          
        when homecursor=>  --resets the cursor back to beginning of line
		LED1 <= "1111000";--7
        
		  if count < setup_delay then
	          lcd_enable <= '1';  -- enable LCD
		  else
			  lcd_enable <= '0';
		  end if;
  
          lcd_data<= HOME;  --sets cursor to beginning
          lcd_rs<='0';
  		  lcd_rw<='0';

		 if count = big_delay then
		    prev_state <= homecursor;
            state<=clear; 
            count:=0;      
          else
            count:=count+1;
          end if;
          
      end case;
    end if;
  end process;
end architecture Display;