lcd display

Altera_Forum · ‎12-07-2012

hi i'm beginner to vhdl. i'm write a vhdl code to display characters on lcd using de2 board. it display different characters for different input from 000 to 111.

i'm already compile the code in quartus and there are no error. however when i download the program on de2 board the lcd was not display anything.

where am i done wrong....please help me...tq

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

entity lcd is

port ( w : in std_logic_vector( 2 downto 0);

rs : out bit;

rw : out bit;

db : out bit_vector(7 downto 0);

lcd_on :out bit;

lcd_blon : out bit);

end lcd;

architecture main of lcd is

signal output : std_logic_vector(2 downto 0);

begin

process(output)

begin

lcd_on<='1';

lcd_blon<='1';

output <= w;

case output is

when "000"=>

rs<='1';

rw<='0';

db<=x"4E",x"4F",x"52",x"4D",x"41",x"4C";

when "001"=>

rs<='1';

rw<='0';

db<=x"4C",x"45",x"56",x"45",x"4C",x"20",x"31";

when "010"=>

rs<='1';

rw<='0';

db<=x"4C",x"45",x"56",x"45",x"4C",x"20",x"32";

when "011"=>

rs<='1';

rw<='0';

db<=x"4D",x"4F",x"44",x"45",x"52",x"41",x"54",x"45";

when "100"=>

rs<='1';

rw<='0';

db<=x"46",x"4C",x"4F",x"4F",x"44",x"20",x"5A",x"4F",x"4E",x"45";

when "101"=>

rs<='1';

rw<='0';

db<=x"44",x"41",x"4E",x"47",x"45",x"52",x"20",x"5A",x"4F",x"4E",x"45";

when "110"=>

rs<='1';

rw<='0';

db<=x"45",x"58",x"54",x"52",x"45",x"4D",x"45",x"4C",x"59",x"20",x"44",x"41",x"4E",x"47",x"45",x"52";

when "111"=>

rs<='1';

rw<='0';

db<=x"4D",x"41",x"58",x"49",x"4D",x"55",x"4D",x"20",x"5A",x"4F",x"4E",x"45";

end case;

end process;

end main;

Altera_Forum · ‎12-10-2012

anyone have suggestion please...

thank you..

Altera_Forum · ‎12-10-2012

You don't have any delay in your code. For example in this linedb<=x"4D",x"41",x"58",x"49",x"4D",x"55",x"4D",x"20 ",x"5A",x"4F",x"4E",x"45";the synthesizer will just see that you assign all those values to db successively with no delay, and will just simplify it todb<=x"45";

You need to add a clock input to your process and do things in sequence, for example by using a state machine, a counter to know which data word to send next, and possibly another counter to implement delays. The LCD datasheet should tell you how much you will need to wait between two states.