library ieee;

use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity heartbeat is
generic (
	divider : std_logic_vector(31 downto 0) := "00000000001111101111000101001000"
);

port (
	clk_i : in std_logic;
	nrst_i : in std_logic;
	led2_o : out std_logic;
	led3_o : out std_logic;
	led4_o : out std_logic;
	led5_o : out std_logic;
	led6_o : out std_logic;
	led7_o : out std_logic;
	led8_o : out std_logic;
	led9_o : out std_logic
);   

end heartbeat;

architecture rtl of heartbeat is
begin

process(clk_i, nrst_i)
variable counter : std_logic_vector(31 downto 0);
variable state : std_logic_vector(7 downto 0) := "00000001";
variable direction : std_logic := '0';
begin

if (rising_edge(clk_i)) then
	if nrst_i = '0' then
		counter := (others => '0');
        else
		led2_o <= state(0);
		led3_o <= state(1);
		led4_o <= state(2);
		led5_o <= state(3);
		led6_o <= state(4);
		led7_o <= state(5);
		led8_o <= state(6);
		led9_o <= state(7);
		counter := counter + 1;
		if counter = divider then
			if state(7) = '1' then
				direction := '1';
			end if;

			if state(0) = '1' then
				direction := '0';
			end if;

			if direction = '0' then
				state(7 downto 1) := state(6 downto 0);
				state(0) := '0';
			else
				state(6 downto 0) := state(7 downto 1);
				state(7) := '0';
			end if;
			counter := (others => '0');
	        end if;
	end if;
end if;
end process;
end architecture;