----------------------------------------------------------------------------------
-- Company:
-- Engineer:
--
-- Create Date:    20:11:46 05/22/2019
-- Design Name:
-- Module Name:    rs232 - Behavioral
-- Project Name:
-- Target Devices:
-- Tool versions:
-- Description:
--
-- Dependencies:
--
-- Revision:
-- Revision 0.01 - File Created
-- Additional Comments:
--
----------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

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

entity rs232 is
    Port ( clk_i : in  STD_LOGIC;
           rst_i : in  STD_LOGIC;
           RXD_i : in  STD_LOGIC;
              led : out STD_LOGIC_VECTOR(7 downto 0);
           TXD_o : out  STD_LOGIC := '1');
end rs232;

architecture Behavioral of rs232 is
signal data : STD_LOGIC_VECTOR(7 downto 0):=(others => '0');
signal flipflop: std_logic := '1';
signal slopping_edge: std_logic := '0';
signal RXD_now: std_logic;
signal RXD_before: std_logic;
signal data_receiving: std_logic := '0';
signal data_sending: std_logic := '0';
--signal RXD_index: integer := 0;

begin

led <= data;
receiver: process(clk_i, rst_i)
variable counter : integer := 0;
variable RXD_index : integer := 0;
begin
    if rst_i = '1' then
     flipflop <= '1';
     RXD_now <= '1';
     RXD_before <= '1';
     slopping_edge <= '0';
     counter := 0;
     RXD_index := 0;
     data_receiving <= '0';
     data <= (others => '0');
     elsif rising_edge(clk_i) then
        flipflop <= RXD_i;
          RXD_now <= flipflop;
        if RXD_now = '0' and RXD_before = '1' and data_receiving = '0' then
            slopping_edge <= '1'; --opadajace
        end if;

         if slopping_edge = '1' then
            if counter = 2604 and RXD_now = '0' then
                data_receiving <= '1';
                counter := -1;
            end if;
                counter := counter + 1;
         end if;
        if data_receiving = '1' then
            slopping_edge <= '0';
            if counter = 5208 then
                data(RXD_index) <= RXD_now;
                RXD_index := RXD_index + 1;
                counter := -1;
                if RXD_index = 8 then
                    RXD_index := 0;
                    data_receiving <= '0';
                end if;
            end if;
            counter := counter + 1;
        end if;
     RXD_before <= RXD_now;
     end if;
end process;

transmiter: process(clk_i, rst_i)
variable counter : integer := 0;
variable TXD_index : integer := 0;
begin
    if rst_i = '1' then
    data_sending <= '0';
    counter := 0;
    TXD_index := 0;
    TXD_o <= '1';
    elsif(rising_edge(clk_i)) then
    if(data_receiving = '0' and data /= "00000000") then
        if(data_sending = '0') then
            TXD_o <= '0';
            data_sending <= '1';
            --counter := 0;
        else
            TXD_o <= '1';

        end if;
    end if;

    if(data_sending = '1' and counter = 5208) then
        if counter = 5208 then
            if TXD_index = 8 then
                TXD_index := 0;
                TXD_o <= '1';
                data_sending <= '0';
            else
            TXD_o <= data(TXD_index);
            TXD_index := TXD_index + 1;
            end if;
            counter := 0;
        else counter := counter +1;
        end if;
    end if;
    end if;
--  if(data_receiving = '0') then
--      case TXD_index is
--      when 0 => TXD_o <= '0';
--      TXD_index := TXD_index + 1;
--      when 1 to 8 => if counter = 5208 then TXD_o <= data(TXD_index-1);
--      TXD_index := TXD_index + 1;
--      end if;
--      when others => if counter = 5208 then TXD_o <= '1';
--      counter := -1;
--      TXD_index := 0;
--      end if;
--      end case;
--      counter := counter + 1;
--  end if;
--
--  if(data_receiving = '0') then
--      if TXD_index = 0 then
--          TXD_o <= '0';
--          TXD_index := 1;
--          --start <= '1';
--      elsif TXD_index 1 to 8 then
--          if(counter = 5208) then
--              TXD_o <= data(TXD_index);
--              counter := 0;
--          else
--              counter := counter + 1;
--          end if;
--      else
--          TXD_o <= '1';
--      end if;
--  else
--      TXD_o <= '1';
--  end if;
end process;
end Behavioral;