Merge branch 'dev' into ppu-interface

1 files changed, 69 insertions, 0 deletions

diff --git a/basys3/basys3.srcs/apu_lut_reader.vhd b/basys3/basys3.srcs/apu_lut_reader.vhd
new file mode 100644
index 0000000..2f92eca
--- /dev/null
+++ b/basys3/basys3.srcs/apu_lut_reader.vhd
@@ -0,0 +1,69 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity apu_lut_reader is
+    port (
+        clk : in std_logic;
+        rst : in std_logic;
+        freq : in std_logic_vector(11 downto 0);
+        wave : in std_logic_vector(1 downto 0);
+        value : out std_logic_vector(7 downto 0)
+    );
+end entity;
+
+architecture behavioral of apu_lut_reader is
+
+    constant AMPLITUDE : natural := 0;
+    constant SAMPLE_SIZE : natural := 256;
+
+    signal idx : unsigned := (others => '0');
+    signal buf : unsigned := (others => '0');
+    
+begin
+
+    process (clk)
+    begin
+        if rst = '1' then
+            idx <= x"00";
+            buf <= x"00";
+            value <= x"00";
+        elsif rising_edge(clk) then
+            -- main code here
+
+            if wave = "00" then     -- Sawtooth
+                value <= std_logic_vector( idx );
+            elsif wave = "01" then  -- Square
+                if idx < (SAMPLE_SIZE/2) then
+                    value <= x"00"; --std_logic_vector( SAMPLE_SIZE-AMPLITUDE ); -- TODO: make so that this work with a changable amplitude (for square wave)
+                else
+                    value <= x"FF";
+                end if;
+            elsif wave = "10" then  -- Triangle
+                if idx < (SAMPLE_SIZE/2) then
+                    value <= std_logic_vector( idx*2 );
+                else
+                    value <= std_logic_vector( (SAMPLE_SIZE-idx)*2 );
+                end if;
+            else-- wave = "11" then -- Noise
+                -- TODO: implement noise function here:
+                value <= x"80"; -- remove this
+            end if;
+
+
+
+            if buf < unsigned(freq) then -- change frequency
+                buf <= buf + 1;
+            else
+                buf <= x"00";
+                if idx < (SAMPLE_SIZE-1) then -- moves to next index value
+                    idx <= idx + 1;
+                else
+                    idx <= x"00";
+                end if;
+            end if;
+
+        end if;
+    end process;
+
+end architecture;