main.vhd

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-- Company: 
-- Engineer: 
-- 
-- Create Date:    11:08:11 08/16/2013 
-- Design Name: 
-- Module Name:    main - Behavioral 
-- Project Name: 
-- Target Devices: 
-- Tool versions: 
-- Description: 
--
-- Dependencies: 
--
-- Revision: 
-- Revision 0.01 - File Created
-- Additional Comments: 
--
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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity main is
    Port ( --CLK : in STD_LOGIC;
           LED146 : out STD_LOGIC;
           LED147 : out STD_LOGIC;
           STATPIN : out STD_LOGIC;
           XMIT : out STD_LOGIC;
           BUTTON : in STD_LOGIC;
           ADC_CLK : in STD_LOGIC;
           ADC_DATA : in STD_LOGIC_VECTOR( 7 downto 0 ) );
end main;

architecture Behavioral of main is
    constant MIN_SPAN : unsigned ( 15 downto 0 ) := X"0258"; -- 600 -> 10us
    constant MAX_SPAN : unsigned ( 15 downto 0 ) := X"04B0"; -- 1200 -> 20us

    signal eventSpan : unsigned ( 15 downto 0 ) := ( others => '0' );
    signal eventPeak : unsigned ( 7 downto 0 ) := ( others => '0' );

    signal count : unsigned ( 25 downto 0 ) := ( others => '0' );
    signal inEvent : boolean := false;

    -- Serial port items
    signal baudCount : unsigned ( 15 downto 0 );
    signal baudClk : STD_LOGIC;

    type SER_BUFFER is array( 63 downto 0 ) of STD_LOGIC_VECTOR( 7 downto 0 );
    signal xmitBuffer : SER_BUFFER;
    signal xmitInIndex : unsigned( 5 downto 0 ) := ( others => '0' );
    signal xmitOutIndex : unsigned( 5 downto 0 ) := ( others => '0' );
    signal xmitState : unsigned( 1 downto 0 ) := ( others => '0' );

begin

    -- Generate the RS-232 baud rate clock
    baudTick : process( ADC_CLK )
    begin
        if( rising_edge( ADC_CLK ) ) then
            baudCount <= baudCount + 63;
            baudClk <= baudCount( 14 );
        end if;
    end process baudTick;

    transmit : process( baudClk )
        variable shiftCount : unsigned( 3 downto 0 );
        variable xmitByte : STD_LOGIC_VECTOR( 7 downto 0 );
    begin
        if( rising_edge( baudClk ) ) then
            case xmitState is
                when "00" => -- Wait state
                    XMIT <= '1';

                    xmitInIndex <= ( xmitInIndex + 1 ) mod 64;

                    if( xmitOutIndex /= xmitInIndex ) then
                        xmitState <= "01";

    --                    xmitByte := xmitBuffer( to_integer( xmitOutIndex ) );
                        xmitByte := X"4A";

                        xmitOutIndex <= ( xmitOutIndex + 1 ) mod 64;
                    end if;

                when "01" => -- Start bit
                    XMIT <= '0';

                    shiftCount := "0000";

                    xmitState <= "10";

                when "10" => -- Data bits
                    XMIT <= xmitByte( to_integer( shiftCount ) );

                    shiftCount := shiftCount + 1;

                    if shiftCount = "1000" then
                        xmitState <= "11";
                    end if;

                when "11" => -- Stop bit
                    XMIT <= '1';

                    xmitState <= "00";

                when others => -- Invalid
                    xmitState <= "00";

            end case;
        end if; -- rising_edge( baudClk )
    end process transmit;

    -- Count up and generate a "pulse" blink
    countUp : process( ADC_CLK )
    begin
        if( rising_edge( ADC_CLK ) ) then
            count <= count + 1;

            if ( count > X"2000000" ) then
                LED147 <= '1';
            else
                LED147 <= '0';
            end if;
        end if;
    end process countUp;

    -- Look for analog events and measure peak and span
    checkADC : process( ADC_CLK )
    begin
        if rising_edge( ADC_CLK ) then
            if inEvent = false then -- Look for start of event

                if ADC_DATA( 7 ) = '1' and BUTTON = '0' then -- Event start
--                    LED146 <= '1';
                    inEvent <= true;

                    eventSpan <= X"0000";
                    eventPeak <= X"00";
                end if;

            else -- In the middle of an event

                eventSpan <= eventSpan + 1;

                if eventSpan > MIN_SPAN and eventSpan < MAX_SPAN then
                    STATPIN <= '1';
                else
                    STATPIN <= '0';
                end if;

                if eventPeak < unsigned( ADC_DATA ) then
                    eventPeak <= unsigned( ADC_DATA );
                end if;

                if ADC_DATA( 7 ) = '0' then -- Event end

                    if eventPeak > X"A0" then
--                        LED146 <= '1';
                    else
--                        LED146 <= '0';
                    end if;

                    STATPIN <= '0';
                    inEvent <= false;
                end if;

            end if; -- inEvent
        end if; -- rising_edge( ADC_CLK )
    end process checkADC;

end Behavioral;