Subversion Repositories gamepads

-------------------------------------------------------------------------------

--

-- A testbench model for the

-- GCpad controller core

--

-- $Id: gcpad_mod.vhd 41 2009-04-01 19:58:04Z arniml $

--

-- Copyright (c) 2004, Arnim Laeuger (arniml@opencores.org)

--

-- All rights reserved

--

-- Redistribution and use in source and synthezised forms, with or without

-- modification, are permitted provided that the following conditions are met:

--

-- Redistributions of source code must retain the above copyright notice,

-- this list of conditions and the following disclaimer.

--

-- Redistributions in synthesized form must reproduce the above copyright

-- notice, this list of conditions and the following disclaimer in the

-- documentation and/or other materials provided with the distribution.

--

-- Neither the name of the author nor the names of other contributors may

-- be used to endorse or promote products derived from this software without

-- specific prior written permission.

--

-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE

-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

-- POSSIBILITY OF SUCH DAMAGE.

--

-- Please report bugs to the author, but before you do so, please

-- make sure that this is not a derivative work and that

-- you have the latest version of this file.

--

-- The latest version of this file can be found at:

--      http://www.opencores.org/cvsweb.shtml/gamepads/

--

-- The project homepage is located at:

--      http://www.opencores.org/projects.cgi/web/gamepads/overview

--

-------------------------------------------------------------------------------

library ieee;

use ieee.std_logic_1164.all;

entity gcpad_mod is

  generic (

    clocks_per_1us_g :       natural := 2

  );

  port (

    clk_i            : in    std_logic;

    pad_data_io      : inout std_logic;

    rx_data_i        : in    std_logic_vector(63 downto 0)

  );

end gcpad_mod;

architecture behav of gcpad_mod is

  -----------------------------------------------------------------------------

  -- Procedure wait_n_us

  --

  -- Purpose:

  --   Waits for the given number of clk_i cycles.

  --

  procedure wait_n_us(clocks : in natural) is

  begin

    wait until clk_i = '0';

    for i in 1 to clocks loop

      wait until clk_i = '1';

      wait until clk_i = '0';

    end loop;

  end wait_n_us;

  --

  -----------------------------------------------------------------------------

  signal time_cnt_q : natural;

  signal timeout_s  : boolean;

begin

  -----------------------------------------------------------------------------

  -- Process timeout

  --

  -- Purpose:

  --   Detects a timeout on incoming pad data stream after 5 us of

  --   inactivity. Resynchronizes upon falling edge of pad_data_io.

  --

  timeout: process (clk_i, pad_data_io)

  begin

    if pad_data_io = '0' then

      timeout_s  <= false;

      time_cnt_q <= 0;

    elsif clk_i'event and clk_i = '1' then

      time_cnt_q <= time_cnt_q + 1;

      if time_cnt_q > 5 * clocks_per_1us_g then

        timeout_s <= true;

      else

        timeout_s <= false;

      end if;

    end if;

  end process timeout;

  --

  -----------------------------------------------------------------------------

  -----------------------------------------------------------------------------

  -- Process model

  --

  -- Purpose:

  --   Simple model for the functionality of a GC controller pad.

  --

  model: process

    procedure send_packet(packet : in std_logic_vector) is

      variable time_low_v, time_high_v : time;

    begin

      for i in packet'high downto 0 loop

        if packet(i) = '0' then

          time_low_v  := 3 us;

          time_high_v := 1 us;

        else

          time_low_v  := 1 us;

          time_high_v := 3 us;

        end if;

        pad_data_io <= '0';

        wait for time_low_v;

        pad_data_io <= 'H';

        wait for time_high_v;

      end loop;

    end send_packet;

    variable command_v : std_logic_vector(24 downto 0);

    constant id_c      : std_logic_vector(23 downto 0) := "000010010000000000000000";

  begin

    loop

      command_v   := (others => '1');

      pad_data_io <= 'Z';

      -------------------------------------------------------------------------

      -- Step 1:

      -- Receive command and associated data.

      --

      wait until pad_data_io = '0';

      wait for 1 ns;

      for i in 24 downto 0 loop

        -- skip rest if timeout occured

        if not timeout_s then

          wait_n_us(2 * clocks_per_1us_g);

          command_v(i) := pad_data_io;

          if pad_data_io = '0' then

            wait until pad_data_io /= '0';

          end if;

          -- wait for high -> low edge

          wait until (pad_data_io = '0') or timeout_s;

        end if;

        wait for 1 ns;

      end loop;

      -------------------------------------------------------------------------

      -- Detect command and send response

      --

      case command_v(24 downto 17) is

        -- get ID

        when "00000000" =>

          wait_n_us(5 * clocks_per_1us_g);

          send_packet(id_c);

          send_packet("1");

        -- poll status

        when "0H000000" =>

          wait_n_us(5 * clocks_per_1us_g);

          send_packet(rx_data_i);

          send_packet("1");

        when others =>

          null;

      end case;

    end loop;

  end process model;

  --

  -----------------------------------------------------------------------------

end behav;