Matrix Keypad

Matrix keypad consists of a set of buttons similar to an alphanumeric keyboard provided with keys usually marked with letters or numbers and various extra keys. Embedded systems which require user interaction must be interfaced with devices that accept user input such as a keypad.

Interfacing Matrix Keypad with FPGA UDB

The Spartan-3 Primer board has 4×4 Matrix Keypad, indicated as in Figure. Keypads arranged by matrix format, each row and column section pulled by high, all row lines and column lines connected directly by the I/O pins.

Pin Assignment with FPGA UDB

Circuit Diagram to Interface Keypad with FPGA

VHDL Code for Keypad using FPGA/CPLD

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.STD_LOGIC_ARITH.ALL;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

---- Uncomment the following library declaration if instantiating

---- any Xilinx primitives in this code. --library UNISIM;

--use UNISIM.VComponents.all;

LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.ALL;

USE IEEE.STD_LOGIC_ARITH.ALL;

USE IEEE.STD_LOGIC_UNSIGNED.ALL;

entity matrix_keypad is port( clock,rst : in std_logic;

col_line : in std_logic_vector(3 downto 0);

row_line : out std_logic_vector(3 downto 0);

led : out std_logic_vector(15 downto 0) );

end matrix_keypad;

architecture Behavioral of matrix_keypad is signal temp : std_logic_vector(29 downto 0);

begin test: process(clock,rst) is begin if(rst='0')

then led <= "1111111111111111";

elsif rising_edge(clock) then temp <= temp + 1;

case temp(10 downto 8) is when "000" => row_line <= "0111";

--first row when "001" => if col_line = "0111" then led <= "0011001100110011";

-- 3 elsif col_line = "1011" then led <= "0010001000100010";

-- 2 elsif col_line = "1101" then led <= "0001000100010001";

-- 1 elsif col_line = "1110" then led <= "0000000000000000";

-- 0 end if; when "010" => row_line <= "1011";

--second row when "011" => if col_line = "1110" then led <= "0100010001000100";

-- 4 elsif col_line = "1101" then led <= "0101010101010101";

-- 5 elsif col_line = "1011" then led <= "0110011001100110";

-- 6 elsif col_line = "0111" then led <= "0111011101110111";

-- 7 end if; when "100" => row_line <= "1101";

--third row when "101" => if col_line = "1110" then led <= "1000100010001000";

-- 8 elsif col_line = "1101" then led <= "1001100110011001";

-- 9 elsif col_line = "1011" then led <= "1010101010101010";

-- a elsif col_line = "0111" then led <= "1011101110111011";

-- b end if; when "110" => row_line <= "1110";

--fourth row when "111" => if col_line = "1110" then led <= "1100110011001100";

-- C elsif col_line = "1101" then led <= "1101110111011101";

-- d elsif col_line = "1011" then led <= "1110111011101110";

-- e elsif col_line = "0111" then led <= "1111111111111111";

-- f end if; when others => led <= "0000000000000000";

end case;

end if;

end process;

end Behavioral;