Incrementing Seven Segment by Using Push Buttons

[khan303]

My fpga is spartan 3E-100 Cp132 (BASYS2). I have four push buttons as my inputs and I want to increment the four digits on 7-segment of the board by using them. The VHDL code is below:

 entity main is
    port(b1,b2,b3,b4 : in STD_LOGIC;
          clk         : in STD_LOGIC;
          sseg        : out STD_LOGIC_VECTOR(0 to 6);
          anodes      : out STD_LOGIC_VECTOR(3 downto 0);
          reset           : in STD_LOGIC
          );
end main;

architecture Behavioral of main is
    signal bcd1, bcd2, bcd3, bcd4 : STD_LOGIC_VECTOR (3 downto 0);
    signal clk2 : STD_LOGIC;
    signal pushbuttons : STD_LOGIC_VECTOR(3 downto 0);
    signal db_pushbuttons : STD_LOGIC_VECTOR(3 downto 0);
    signal counter : STD_LOGIC_VECTOR(1 downto 0);
    signal clk_divider : STD_LOGIC_VECTOR(20 downto 0);
    component Debounce is
        port( cclk : in STD_LOGIC;
                inp : in STD_LOGIC_VECTOR(3 downto 0);
                cclr : in STD_LOGIC;
                db  : out STD_LOGIC_VECTOR(3 downto 0)
                );
    end component;
begin
    pushbuttons <= b4 & b3 & b2 & b1;
    Db : Debounce port map
            ( cclk => clk2,
              inp => pushbuttons,
              cclr => reset,
              db  => db_pushbuttons);

process (clk)
begin
    if rising_edge(clk) then
        if clk_divider <= "1100001101010000" then
            clk_divider <= clk_divider + 1;
            clk2 <= '0';
        else
            clk_divider <= (others => '0');
            clk2 <= '1';
        end if;
    end if;
end process;

process (clk2, reset)
begin
    if reset = '1' then
        -- do something here
        bcd1 <= "0000";
        bcd2 <= "0000";
        bcd3 <= "0000";
        bcd4 <= "0000";
    elsif rising_edge(clk2) then
        counter <= counter + 1;
        if db_pushbuttons(0) = '1' then -- db_b1
            if bcd1 <= "1000" then
                bcd1 <= bcd1 + 1;
            else
                bcd1 <= "0000";
            end if;
        elsif db_pushbuttons(1) = '1' then -- db_b2
            if bcd2 <= "1000" then
                bcd2 <= bcd2 + 1;
            else
                bcd2 <= "0000";
            end if;
        elsif db_pushbuttons(2) = '1' then -- db_b3
            if bcd3 <= "1000" then
                bcd3 <= bcd3 + 1;
            else
                bcd3 <= "0000";
            end if;
        elsif db_pushbuttons(3) = '1' then --db_b4
            if bcd4 <= "1000" then
                bcd4 <= bcd4 + 1;
            else
                bcd4 <= "0000";
            end if;
        end if;
    end if;
end process;

process (counter, bcd1, bcd2, bcd3, bcd4)
    variable display : STD_LOGIC_VECTOR(3 downto 0);
begin
    case counter is
        when "00" => anodes <= "1110"; display := bcd1;
        when "01" => anodes <= "1101"; display := bcd2;
        when "10" => anodes <= "1011"; display := bcd3;
        when "11" => anodes <= "0111"; display := bcd4;
        when others => null;
    end case;

    case display is
        when "0000" => sseg <= "0000001"; --0
        when "0001" => sseg <= "1001111"; --1
        when "0010" => sseg <= "0010010"; --2
        when "0011" => sseg <= "0000110"; --3
        when "0100" => sseg <= "1001100"; --4
        when "0101" => sseg <= "0100100"; --5
        when "0110" => sseg <= "0100000"; --6
        when "0111" => sseg <= "0001111"; --7
        when "1000" => sseg <= "0000000"; --8
        when "1001" => sseg <= "0000100"; --9
        when others => sseg <= "0010000"; --e, represents error
    end case;
end process;
end Behavioral;

Every pushbutton should increment the corresponding 7-segment digit (b1 --> rightmost digit and b4--> leftmost digit) by one. The problem is when I push the button, it does the job but not increment it by one but some arbitrary number. The reason is that it increments by one at every rising edge of the clock 2, which happens too quickly due to the frequency of this clock. How can I manage to get rid of this problem? I tried several debouncing code for the push buttons but they weren't helpful so much. I am totally stuck here. I mean there should be a way to do it, right? By the way, the debouncing code that I have been using with the code above is

entity Debounce is
    port(cclk       :   in STD_LOGIC;
          inp    :  in STD_LOGIC_VECTOR(3 downto 0);
          cclr  :  in STD_LOGIC;
          db     :  out STD_LOGIC_VECTOR(3 downto 0)
         );
end Debounce;

architecture Behavioral of Debounce is
    signal delay1, delay2, delay3 : STD_LOGIC_VECTOR(3 downto 0);
begin
    process (cclk, cclr)
    begin
        if cclr = '1' then
            delay1 <= "0000";
            delay2 <= "0000";
            delay3 <= "0000";
        elsif rising_edge(cclk) then
            delay1 <= inp;
            delay2 <= delay1;
            delay3 <= delay2;
        end if;
    end process;
    db <= delay1 and delay2 and delay3;
end Behavioral;

Any help will be appreciated, thanks in advance!

 

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You should add a synchronizer for the four button inputs and then run it into the debounce code.
You need to perform an edge detection on the db output of your Debounce code to get only a single pulse, otherwise it will increment as long as the button is pressed.

You're dividing the input clock by 50,002. You probably wanted to do by 50,000 so you need to replace the <= with < and compare with the value 49,999.

You should also synchronize the release of reset, otherwise you will have issues with recovery/removal timing. You will also require a debounce on the reset if it's using a pushbutton.

Regards

 

[khan303]

Thanks for the reply! Now I have a sense that I am finally close to the solution. But if you explain how I can add a synchronizer to the code a bit further, I will be very glad. I mean first thing that comes to my mind is to add a signal in the Debounce code to hold the previous values of the pushbuttons, and if they are 1's than I shouldn't increment the bcd's at all. But incrementation is already happening in the main code, so how can I make changes to the Debounce code so as to get the desired result? By the way, my mistake that I divided the input clock by 50,002 not 50,000. Thanks for the heads-up.

 

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To synchronize the cross clock domain signal register it 2-3 times in the new clock domain before using it. The synchronized signal can then be debounced followed by edge detection in the new clock domain.