refactor vga and move pixeldata to pixeldata-square

2 files changed, 80 insertions, 60 deletions

diff --git a/src/pixeldata.vhd b/src/pixeldata-square.vhd
index 0fa229f..0fa229f 100644
--- a/src/pixeldata.vhd
+++ b/src/pixeldata-square.vhd
diff --git a/src/vga.vhd b/src/vga.vhd
index 16becca..9ba5797 100644
--- a/src/vga.vhd
+++ b/src/vga.vhd
@@ -1,60 +1,80 @@
-library ieee;

-use ieee.std_logic_1164.all;

-use ieee.std_logic_arith.all;

-use ieee.std_logic_unsigned.all;

-

-entity vga is

-	port (

-		clk25, reset: in std_logic;

-		x, y: out std_logic_vector(9 downto 0);

-		rgb: in std_logic_vector(11 downto 0);

-		red, green, blue: out std_logic_vector(3 downto 0);

-		hsync, vsync: out std_logic);

-end vga;

-

-architecture Behavioral of vga is

-	signal hcount: std_logic_vector(9 downto 0);

-	signal vcount: std_logic_vector(9 downto 0);

-begin

-

-	process (clk25) 

-	begin

-		if rising_edge(clk25) then

-			if (hcount >= 144) and (hcount < 784) and (vcount >= 31) and (vcount < 511) then

-				x <= hcount - 144;

-				y <= vcount - 31;

-				red <= rgb(11 downto 8);

-				green <= rgb(7 downto 4);

-				blue <= rgb(3 downto 0);

-			else

-				red <= x"0";

-				green <= x"0";	

-				blue <= x"0";

-			end if;

-

-			if hcount < 97 then

-				hsync <= '0';

-			else

-				hsync <= '1';

-			end if;

-

-			if vcount < 3 then

-				vsync <= '0';

-			else

-				vsync <= '1';

-			end if;

-

-			hcount <= hcount + 1;

-

-			if hcount = 800 then

-				vcount <= vcount + 1;

-				hcount <= (others => '0');

-			end if;

-

-			if vcount = 521 then				

-				vcount <= (others => '0');

-			end if;

-		end if;

-	end process;

-end Behavioral;

-

+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.std_logic_arith.all;
+use ieee.std_logic_unsigned.all;
+
+entity vga is
+	port (
+		clk25, reset: in std_logic;
+		x, y: out std_logic_vector(9 downto 0);
+		rgb: in std_logic_vector(11 downto 0);
+		red, green, blue: out std_logic_vector(3 downto 0);
+		hsync, vsync: out std_logic);
+end vga;
+
+architecture Behavioral of vga is
+	signal hcount: std_logic_vector(9 downto 0);
+	signal vcount: std_logic_vector(9 downto 0);
+
+	-- timing info from http://www.tinyvga.com/vga-timing/640x480@60Hz
+	constant screen_sz_ver: natural := 480; -- screen size vertical
+	constant pulse_ver: natural := 2; -- vertical sync pulse width
+	constant front_porch_ver: natural := 10; -- vertical front porch pulse width
+	constant back_porch_ver: natural := 33; -- vertical back porch pulse width
+	constant screen_sz_hor: natural := 640; -- screen size horizontal
+	constant pulse_hor: natural := 96; -- horizontal sync pulse width
+	constant front_porch_hor: natural := 16; -- horizontal front porch pulse width
+	constant back_porch_hor: natural := 48; -- horizontal back porch pulse width
+begin
+
+	process (clk25)
+	begin
+		if rising_edge(clk25) then
+			-- display area
+			if (hcount >= (pulse_hor + back_porch_hor)) and
+			   (hcount < (pulse_hor + back_porch_hor + screen_sz_hor)) and
+			   (vcount >= (pulse_ver + back_porch_ver)) and
+			   (vcount < (pulse_ver + back_porch_ver + screen_sz_ver)) then
+				x <= hcount - (pulse_hor + back_porch_hor);
+				y <= vcount - (pulse_ver + back_porch_ver);
+				red <= rgb(11 downto 8);
+				green <= rgb(7 downto 4);
+				blue <= rgb(3 downto 0);
+			else
+				-- turn off RGB during sync pulses
+				red <= x"0";
+				green <= x"0";
+				blue <= x"0";
+			end if;
+
+			-- vertical pulse
+			if hcount <= pulse_hor then
+				hsync <= '0';
+			else
+				hsync <= '1';
+			end if;
+
+			-- horizontal pulse
+			if vcount <= pulse_ver then
+				vsync <= '0';
+			else
+				vsync <= '1';
+			end if;
+
+			-- update horizontal line counter
+			hcount <= hcount + 1;
+
+			-- horizontal line counter overflow
+			if hcount = (front_porch_hor + back_porch_hor + pulse_hor + screen_sz_hor) then
+				vcount <= vcount + 1;
+				hcount <= (others => '0');
+			end if;
+
+			-- vertical line counter overflow
+			if vcount = (front_porch_ver + back_porch_ver + pulse_ver + screen_sz_ver) then
+				vcount <= (others => '0');
+			end if;
+		end if;
+	end process;
+end Behavioral;
+