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How to Interface VGA with FPGA/CPLD UDB

VGA

A Video Graphics Array (VGA) connector is a three-row 15-pin DE-15 connector. The 15-pin VGA connector is found on many video cards, computer monitors, and some high definition television sets. On laptop computers or other small devices, a mini-VGA port is sometimes used in place of the full-sized VGA connector.

Interfacing VGA with FPGA/CPLD UDB

The Spartan-3 Primer board has 3-Bit VGA, indicated as in Figure. As shown in Figure, the Spartan3 FPGA/CPLD UDB controls five VGA signals: Red (R) its 1st pin in connector, Green (G) its 2nd pin, Blue (B) its 3rd pin, Horizontal Sync (HS) 13th pin, and Vertical Sync (VS) its 14th pin, all available on the VGA connector. The FPGA/CPLD pins that drive the VGA port appear in Table. A video controller circuit must be created in the FPGA to drive the sync and color signals with the correct timing in order to produce a working display system.

 

Pin Assignment with Spartan-3 Primer FPGA/CPLD



Signals

PIN NAME

RED

VGA_RED

GREEN

VGA_GREEN

BLUE

VGA_BLUE

Horizontal Sync (Hs)

VGA_HS

Vertical Sync (Vs)

VGA_VS

 



Note: Please refer User Manual for Pin number of FPGA/CPLD

Schematics to Interface VGA with FPGA/CPLD UDB





VHDL Code for VGA using FPGA/CPLD UDB

***************************************************************************************

Title : Program for VGA to LED Display

***************************************************************************************

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
 
entity VGA is
port(clk50_in : in std_logic;         -----system clock i/p
       red       : out std_logic;         -----primrary colour output
       green     : out std_logic;
       blue     : out std_logic;
       hs_out   : out std_logic;         ------horizontal control signal
       vs_out   : out std_logic);         ------vertical   control signal
end VGA;
 
architecture Behavioral of VGA is
 
signal clk25             : std_logic;
signal hs : std_logic_vector (9 downto 0);
signal vs : std_logic_vector (9 downto 0);
begin
 
-- generate a 25Mhz clock
process (clk50_in)
begin
if clk50_in'event and clk50_in='1' then
if (clk25 = '0') then              
clk25 <= '1';
else
clk25 <= '0';
end if;
end if;
end process;
------display logic for message "PANTECH SOLUTIONS"
process (clk25)
begin
if clk25'event and clk25 = '1' then
if hs = "0011001000" and vs >= "0011001000" and vs <= "0011111010" then ---horizantal and vertical line display constraint
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0011001000" and vs >= "0100101100" and vs <= "0101000101" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0011111010" and vs >= "0011001000" and vs <= "0011100001" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0011111010" and vs >= "0101000101" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0100000100" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0100000100" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0100110110" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0100110110" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0101000000" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0101000000" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0101110010" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0101111110" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0110101110" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0110010101" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0110111000" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0111010001" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "0111110100" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "1000001101" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "1000110000" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "1001100010" and vs >= "0011001000" and vs <= "0011111010" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "1000110000" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "1001100010" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "1001101100" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
elsif hs = "1010011110" and vs >= "0100101100" and vs <= "0101011110" then
red <= '1' ;
blue <= '0';
green <= '0' ;
--------------------------------------------------------------------------------
else                     ----------blank signal display
red <= '0' ;
blue <= '0';
green <= '0' ;
end if;
if (hs > "0000000000" )
and (hs < "0001100001" ) -- 96+1   -----horizontal tracing
then
hs_out <= '0';
else
hs_out <= '1';
end if;
if (vs > "0000000000" )
and (vs < "0000000011" ) -- 2+1   ------vertical tracing
then
vs_out <= '0';
else
vs_out <= '1';
end if;
hs <= hs + "0000000001" ;
if (hs= "1100100000") then     ----incremental of horizontal line
vs <= vs + "0000000001";       ----incremental of vertical line
hs <= "0000000000";
end if;
if (vs= "1000001001") then                 
vs <= "0000000000";
end if;
end if;
end process;
end Behavioral;

User Constraint File

NET "blue"  LOC = "p26"  ;
NET "clk50_in"  LOC = "p181"  ;
NET "green"  LOC = "p24"  ;
NET "hs_out"  LOC = "p21"  ;
NET "red"  LOC = "p27"  ;
NET "vs_out"  LOC = "p22"  ;