blob: 6039798d6114911316f7ef0a7eda18a72d368c91 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
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;
|