Add dsp

With:
- LED control
- UART
- PDM out
- square wave generator (DMA to PDM out (was it really necessary?))
- sample program that plays a square wave from UART values

dsp/boot_rom.vhdl.in

@@ -0,0 +1,49 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity boot_rom is
+  generic
+  (
+    addressWidth : in positive := 16;
+    busWidth : in positive := 16
+  );
+  port
+  (
+    clk: in std_logic;
+    code_addr : in std_logic_vector(15 downto 0);
+    code_out : out std_logic_vector(15 downto 0);
+
+    data_addr : in std_logic_vector(15 downto 0);
+    data_out : out std_logic_vector(15 downto 0)
+  );
+end boot_rom;
+
+architecture Behavioral of boot_rom is
+  constant alignment: positive := busWidth / 8;
+  constant romsize: natural := $nwords;
+
+  type romtype is array(0 to romsize - 1) of std_logic_vector(15 downto 0);
+  signal romdata: romtype := (
+$words
+  );
+begin
+
+  process(clk) is
+    variable code_index: natural;
+    variable data_index: natural;
+  begin
+    if rising_edge(clk) then
+    code_index := to_integer(unsigned(code_addr)) / alignment;
+    if code_index < romsize then
+      code_out <= romdata(code_index);
+    else
+      code_out <= x"0000";
+    end if;
+
+    data_index := to_integer(unsigned(data_addr)) / alignment;
+     data_out <= romdata(data_index);
+     end if;
+  end process;
+
+end Behavioral;