DE2 Quartus debounced circuit

Hello,

I made a simplest program for hex counter it supposed to count push-button clicks.

It present the result on a single 7seg display and 4 LEDs, unfortunately I've got a bouncing problem.

I'm using a Altera Cyclone II BAIXUN ASK2CB dev. board it has on board push-button

Can you please suggest how can i debounce it, so the bits go one by one?

Here is my code:

========================================

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.STD_LOGIC_ARITH.ALL;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity test is

port (Y : out std_logic_vector (6 downto 0); -- 7 seg digit

B : out std_logic;

pb : in std_logic;

count : out std_logic_vector(3 downto 0);

reset :in std_logic

);

end entity test;

architecture Behavioral of test is

signal c: std_logic_vector(3 downto 0) :=(others => '0'); --initializing count to zero.

begin

counting: process(pb,reset) is

begin

if rising_edge (pb) then

if(c = "1111") then -- when count reaches its maximum(that is 15) reset it to 0

c <="0000";

end if;

c <= c+'1'; --increment count at every positive edge of clk.

end if;

if(reset='0') then --when reset equal to '0' make count equal to 0.

c <=(others => '0'); -- c ="0000"

end if;

case c is

when "0000"=>Y<="1000000";-- 0

when "0001"=>Y<="1111001";-- 1

when "0010"=>Y<="0100100";-- 2

when "0011"=>Y<="0110000";-- 3

when "0100"=>Y<="0011001";-- 4

when "0101"=>Y<="0010010";-- 5

when "0110"=>Y<="0000010";-- 6

when "0111"=>Y<="1111000";-- 7

when "1000"=>Y<="0000000";-- 8

when "1001"=>Y<="0010000";-- 9

when "1010"=>Y<="0001000";-- A

when "1011"=>Y<="0000011";-- b

when "1100"=>Y<="1000110";-- C

when "1101"=>Y<="0100001";-- d

when "1110"=>Y<="0000110";-- E

when "1111"=>Y<="0001110";-- F

when others=>Y<="1111111";-- in other cases balnk

end case;

end process counting;

B<='0';

count<=c;

end architecture Behavioral;

==========================================

you shouldn't use the push button as clock input, it isvery unreliable and sensitive to bounces, as you discovered.

Instead, use a regular clock (I'm sure the board has an oscillator you can use) and monitor the pb signal on each clock cycle. You can detect a change on the button status by comparing the current value of pb with the previous one. You will also probably need to implement a delay for proper debouncing.

Thank you Daixiwen!

I see, anyway i tried to make a delay but nothing seem to work yet, still trying.

I'm a beginner, so i'll will be really glad if you can help me with solving upon my code,

to understand it better! If its not to much to ask!

Hi Daixiwen and thanks,

Sorry for a long time no answer. Finally solved the problem. using the following code:

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

entity debounce is

generic(

counter_size : INTEGER := 19); --counter size (19 bits gives 10.5ms with 50MHz clock)

port(

Digit : out std_logic_vector (6 downto 0); -- 7 seg digit

hex_count : out std_logic_vector(3 downto 0); -- Hexadecimal result

clk, reset, button : in std_logic; --input signals

Digit_en : out std_logic); -- 7 seg digit enable

end debounce;

architecture logic of debounce is

signal counter : std_logic_vector(3 downto 0) :=(others => '0'); --initializing count to zero.

signal flipflops : std_logic_vector(1 downto 0); --input flip flops

signal counter_out : std_logic_vector(counter_size downto 0) := (others => '0'); --counter output

signal counter_set : std_logic; --sync reset to zero

signal result : std_logic; --debouncer result

begin

counter_set <= flipflops(0) xor flipflops(1); --determine when to start/reset counter

process(clk)

begin

if(clk'event and clk = '1') then

flipflops(0) <= button;

flipflops(1) <= flipflops(0);

if(counter_set = '1') then --reset counter because input is changing

counter_out <= (others => '0');

elsif(counter_out(counter_size) = '0') then --stable input time is not yet met

counter_out <= counter_out + 1;

else --stable input time is met

result <= not flipflops(1);

end if;

end if;

end process;

process(result)

begin

if(reset='0') then --when reset equal to '0' make count equal to 0.

counter <=(others => '0'); -- c ="0000"

elsif(result'event and result = '1') then

if(counter = "1111") then -- when count reaches its maximum(that is 15) reset it to 0

counter <="0000";

end if;

counter <= counter+'1'; --increment count at every positive edge of clk.

end if;

case counter is

when "0000"=>Digit<="1000000";-- 0

when "0001"=>Digit<="1111001";-- 1

when "0010"=>Digit<="0100100";-- 2

when "0011"=>Digit<="0110000";-- 3

when "0100"=>Digit<="0011001";-- 4

when "0101"=>Digit<="0010010";-- 5

when "0110"=>Digit<="0000010";-- 6

when "0111"=>Digit<="1111000";-- 7

when "1000"=>Digit<="0000000";-- 8

when "1001"=>Digit<="0010000";-- 9

when "1010"=>Digit<="0001000";-- A

when "1011"=>Digit<="0000011";-- b

when "1100"=>Digit<="1000110";-- C

when "1101"=>Digit<="0100001";-- d

when "1110"=>Digit<="0000110";-- E

when "1111"=>Digit<="0001110";-- F

when others=>Digit<="1111111";-- in other cases balnk

end case;

end process;

Digit_en<='0';

hex_count<=counter;

end;