library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.fixed_float_types.all;
use ieee.fixed_pkg.all;
entity low_pass_filter is
  generic (integer_bits : integer; fraction_bits : integer);
  port (clock : in std_logic;
        reset : in std_logic;
        sample : in sfixed(integer_bits-1 downto -fraction_bits);
        sample_ready : in std_logic;
        output : out sfixed(integer_bits-1 downto -fraction_bits);
        output_ready : out std_logic);
end;

architecture behaviour of low_pass_filter is

  constant order : natural := 16;
  constant counter_bits : natural := 5;

  -- coefficient store
  subtype coeff_type is sfixed(1 downto -32);
  type coeff_array_type is array (natural range 0 to order) of coeff_type;
  constant coefficients : coeff_array_type :=
    (
      B"00_00001001011011111101001111001101",  -- 0.0368626
      B"00_00000101000000101101011101110001",  -- 0.019574609
      B"11_11111010000100001100010110000010",  -- -0.023181587
      B"11_11110000111000101111010111011001",  -- -0.05903686
      B"11_11110011011010110101111110100000",  -- -0.04914286
      B"00_00000110000111010110010111000001",  -- 0.02388607
      B"00_00100011100101110101010001000101",  -- 0.13902785
      B"00_00111110100110010011100100100010",  -- 0.2445255
      B"00_01001001100000101010101111101100",  -- 0.28715014
      B"00_00111110100110010011100100100010",  -- 0.2445255
      B"00_00100011100101110101010001000101",  -- 0.13902785
      B"00_00000110000111010110010111000001",  -- 0.02388607
      B"11_11110011011010110101111110100000",  -- -0.04914286
      B"11_11110000111000101111010111011001",  -- -0.05903686
      B"11_11111010000100001100010110000010",  -- -0.023181587
      B"00_00000101000000101101011101110001",  -- 0.019574609
      B"00_00001001011011111101001111001101"   -- 0.0368626
    );

  -- internal signals
  signal address : unsigned(counter_bits-1 downto 0) := (others => '0');
  signal coefficient : sfixed(integer_bits-1 downto -fraction_bits);

begin

  filter : entity work.filter_core
    generic map(integer_bits, fraction_bits, counter_bits, order)
    port map (clock, reset,
              sample, sample_ready,
              address, coefficient,
              output, output_ready);

  coefficient <= resize(coefficients(to_integer(address)), coefficient);

end;