fpga-controls

This is a SystemVerilog solution to handle multi-directional inputs in attempt to predict the player's intentions.

fpga-controls is part of the MiSTer Enhanced Experience project aimed at improving the MiSTer experience. For more information, please check out the Enex wiki.

A lot of systems and software are designed to work best on the controller shipped with them. As most users use their favorite controllers to play them on FPGA (like the awesome MiSTer FPGA system), more capable controllers are able to send inputs that the original systems were never prepared for. The biggest example is playing 4-way-only joystick systems on a dpad or arcade sticks with a 8-way or round gate.

Diagonal inputs can easily be sent by accident when you're quickly changing directions. This makes it quite difficult to play games shipped with 2-way or 4-way only controllers. This is a solution to make the controls feel responsive and predictable in those systems.

Features

• Horizontal & Vertical Simultaneous Opposite Cardinal Direction (SOCD) Cleaner
• User Intent Prediction for Diagonal Inputs
• Optimal Behavior for Perfect Diagonal Inputs
• Control Override for 2/4-way-only Systems

Implementation

You can use the indiviual modules if you just want one small part of the solution, but for a proper implementation simply use the enhanced2wayjoy/enhanced4wayjoy module in controls_top.sv.

Implement this goodie in just two steps!

1. Include controls_top.sv.

2. Add a User Option (MiSTer, for example, provides core configuration string):

"ODG,Diagonal,Default,Change Direction,Keep Direction,Vertical,Horizontal,Stop;",

3. Wire your inputs in your FPGA core.

[4-Way] (MiSTer):

//  parameters:
//  1. What to do when both Up & Down switches are on: FAVOR_ZERO, FAVOR_UP, FAVOR_DOWN
//  2. What to do when both Left & Right switches are on: FAVOR_ZERO, FAVOR_LEFT, FAVOR_RIGHT
//  3. Favored direction on pure diagonal inputs: DIR_HORIZONTAL, DIR_VERTICAL
//  For detailed documentation, check out the comments in "./controls_top.sv".
enhanced4wayjoy #(FAVOR_ZERO, FAVOR_ZERO, DIR_HORIZONTAL) player1
(
    clk_sys,
    {
        // p1_btn_x: keyboard, joy[x]: game pads
        p1_btn_up    | joy[3],
        p1_btn_down  | joy[2],
        p1_btn_left  | joy[1],
        p1_btn_right | joy[0]
    },
    {m_p1_up, m_p1_down, m_p1_left, m_p1_right}, // Output wire to the core
    status[16:13] // 4bit User Options. Check "[UIPD]" in "./diagonal.sv".
);

[2-Way] (MiSTer):

//  parameters:
//  1. Orientation of the 2-way: DIR_HORIZONTAL, DIR_VERTICAL
//  For detailed documentation, check out the comments in "./controls_top.sv".
enhanced2wayjoy #(DIR_HORIZONTAL) player1
(
    clk_sys,
    {
        // p1_btn_x: keyboard, joy[x]: game pads
        p1_btn_up    | joy[3],
        p1_btn_down  | joy[2],
        p1_btn_left  | joy[1],
        p1_btn_right | joy[0]
    },
    {m_p1_up, m_p1_down, m_p1_left, m_p1_right} // Output wire to the core
);

For more information, check "controls_top.sv". It provides enhanced4wayjoy and enhanced2wayjoy top level modules.

Available User Options

There's no one perfect solution for all 4-way-only games. Each game works best one way while others can be hurt by it. It's best to keep all of these options available for the users to decide.

All Systems

• Default - Does not do anything like before. Unpredictable outcome.

4-Way-Only

• Change Direction - Otherwise known as "Prediction", when diagonal input is received, it assumes the new direction is intended so the direction that was pressed later than the earlier direction is processed. This is the most preferred way and recommended for most systems.
• Keep Direction - The often called "Correction" is a way to respect the earlier direction and correct it to stay on course while ignoring the new direction in the diagonal input.
• Vertical - Always forces* to vertical directions.
• Horizontal - Always forces* to horizontal directions.
• Stop - This "Clear" option assumes the diagonal input is an error, and both input must be stopped to prevent any potential disasters. Some prefer this for games like Tetris.

*Forcing into one direction like this cannot prevent any movements if the opposing movement was pressed first (as we cannot predict future). It still prevents the other direction being pressed further.

Providing User Options

Module parameters are only intended for the developer as the system should always behave in one configuration. They should't be exposed to the user as it is unnecessary.

Users, however, have different preference on how their diagonal direction inputs should be handled. The whole point is to make the controls feel responsive in a preferred way, so they should not be forced to one option. Expose the input [3:0] m_mode of enhanced2wayjoy/enhanced4wayjoy module.