1 files changed, 110 insertions, 0 deletions

diff --git a/FPGA/vhdl/codec_dac.vhd b/FPGA/vhdl/codec_dac.vhd
new file mode 100644
index 0000000..0cfd858
--- /dev/null
+++ b/FPGA/vhdl/codec_dac.vhd
@@ -0,0 +1,110 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity codec_dac is
+  generic (
+    system_frequency : real := 50.0E6; -- 50 MHz
+    sample_rate      : real := 48.0E3; -- 48 kHz        
+          data_width       : positive := 16; -- 16 bits
+          channel_num      : positive := 2   -- dual channel
+  );
+  port (
+   clk            : in  std_logic;                 --
+        resetn         : in  std_logic;                 --
+        go             : in  std_logic;
+        data_in        : in  std_logic_vector(data_width-1 downto 0);
+        -- codec 
+        tempo_dac      : out std_logic;
+        end_dac        : out std_logic;
+        codec_dac_bclk : out std_logic;                 -- B4
+        codec_dac_data : out std_logic;                 -- A4
+        codec_dac_lrck : out std_logic                  -- C6
+  );
+end entity;
+architecture rtl of codec_dac is
+  constant mod_bclk : positive := integer(system_frequency/(2.0*sample_rate*real(data_width)*real(channel_num)));
+  constant mod_lrck : positive := data_width*channel_num/2;
+  type state is (wait_for_go, tx);
+  signal current_state : state;
+  signal next_state    : state;
+  signal ctr_bclk   : natural range 0 to mod_bclk-1;
+  signal ctr_lrck   : natural range 0 to mod_lrck-1;
+  signal reg_data   : std_logic_vector(data_in'range);
+  signal cmd_data   : std_logic_vector(1 downto 0);
+  signal bclk       : std_logic;
+  signal lrck       : std_logic;
+  signal end_bit    : std_logic;
+begin
+  codec_dac_bclk <= bclk;
+  codec_dac_lrck <= lrck;
+  codec_dac_data <= reg_data(reg_data'low);
+  tempo_dac      <= end_bit;
+  end_bit        <= '0' when (ctr_bclk< mod_bclk-1) or bclk='0' 
+                    else '1';
+  -- registers and counters
+  process(clk, resetn) is
+  begin
+    if resetn ='0' then
+          bclk     <= '0';
+          lrck     <= '0';
+          reg_data <= (others => '0');
+          ctr_bclk <= 0;
+          ctr_lrck <= 0;
+          current_state <= wait_for_go;
+        elsif rising_edge(clk) then 
+          current_state <= next_state;
+          if ctr_bclk< mod_bclk-1 then
+            ctr_bclk <= ctr_bclk+1;
+          else
+            ctr_bclk <= 0;       
+            bclk     <=not bclk;    
+          end if;
+          
+          --  data register
+          case cmd_data is
+            when "10"    => reg_data <= data_in;
+            when "11"    => reg_data <= '0'&reg_data(reg_data'high downto 1);
+            when others  => null;
+          end case;
+          
+          if end_bit = '1' then 
+            if ctr_lrck < mod_lrck-1 then
+              ctr_lrck  <= ctr_lrck +1;
+            else
+                    ctr_lrck  <= 0;
+                    lrck      <= not lrck;
+            end if;
+          end if;
+        end if;
+        end process;
+  process(current_state,go,end_bit, ctr_lrck) is
+  begin
+    next_state <= current_state;
+    cmd_data   <= "00";
+    end_dac    <= '1';
+    case current_state is
+      when wait_for_go => if go = '1' then 
+                            next_state <= tx;
+                            cmd_data   <= "10";
+                          end if;
+      when tx          => if end_bit='1' then                            
+                            if ctr_lrck >= mod_lrck-1 then 
+                              if go ='0' then 
+                                next_state <= wait_for_go;
+                              else
+                                cmd_data   <= "10";
+                              end if;
+                            else 
+                              cmd_data   <= "11";  
+                            end if;
+                          end if;
+                          end_dac    <= '0';                          
+    end case;
+  end process;
+end architecture;
+
+                                                                
+                        
+                                        
+