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Merge branch 'gamepad_pmod' into ihp130
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‎README.md‎

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@@ -16,7 +16,7 @@ Atari 2600 fits this goal perfectly thanks to it is minimal hardware design (i.e
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The design is so small that around **40** Atari consoles fit on a silicon die! The silicon area of this design is 0.2 mm2 (1000um x 216um) on a SkyWater 130 nm node.
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Explore chip in [3D directly in the browser](https://gds-viewer.tinytapeout.com/?model=https://rejunity.github.io/tt09-atari-2600/tinytapeout.gds.gltf)!
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Explore chip in [3D directly in the browser](https://gds-viewer.tinytapeout.com/?model=https://rejunity.github.io/tiny-atari-2600/tinytapeout.gds.gltf)!
2020

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This design is submitted for fabrication with [Tiny Tapeout 09](https://tinytapeout.com) via eFabless [CI 2411 Shuttle](https://platform.efabless.com/shuttles/CI%202411). Check status here: https://app.tinytapeout.com/projects/1343
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‎info.yaml‎

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@@ -21,6 +21,7 @@ project:
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- "vga_hvsync_generator.v"
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- "palette_24bpp.v"
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- "qspi_flash.v"
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- "gamepad_pmod.v"
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- "atari2600.v"
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- "6502.v"
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- "ALU.v"
@@ -30,14 +31,14 @@ project:
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# The pinout of your project. Leave unused pins blank. DO NOT delete or add any pins.
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pinout:
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# Inputs
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ui[0]: "UP / Switch 1"
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ui[1]: "DOWN / Switch 2"
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ui[2]: "LEFT / Switch BW"
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ui[3]: "RIGHT / Switch 3"
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ui[4]: "FIRE"
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ui[5]: "Joystick 1 / 2"
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ui[6]: "Switches"
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ui[7]: "RESET"
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ui[0]: "UP / Difficulty Switch P1"
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ui[1]: "DOWN / Difficulty Switch P2"
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ui[2]: "LEFT / Monochrome Switch"
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ui[3]: "RIGHT"
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ui[4]: "FIRE / Gamepad LATCH"
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ui[5]: "SELECT / Gamepad CLK"
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ui[6]: "Switches / Gamepad DATA"
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ui[7]: "START"
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# Outputs
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uo[0]: "R1"

‎src/PIA.v‎

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@@ -55,7 +55,7 @@ module pia (
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case (adr_i)
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7'h00: begin dat_o <= {buttons[6:3], buttons[6:3]}; end// SWCHA
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7'h01: dat_o <= swa_dir; // SWACNT
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7'h02: dat_o <= {~sw[0], ~sw[1], 2'b11, sw[2], 1'b1, buttons[SELECT], buttons[RESET]}; // SWCHB
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7'h02: dat_o <= {~sw[1], ~sw[0], 2'b11, sw[2], 1'b1, buttons[SELECT], buttons[RESET]}; // SWCHB
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7'h03: dat_o <= {2'b0, swb_dir[5:4], 1'b0, swb_dir[2], 2'b0}; // SWBCNT
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7'h04: begin; dat_o <= intim; underflow <= 0; end // INTIM
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7'h05: begin dat_o <= {instat, 6'b0}; instat[0] <= 0; end// INSTAT

‎src/gamepad_pmod.v‎

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/*
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* Copyright (c) 2025 Pat Deegan, https://psychogenic.com
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* SPDX-License-Identifier: Apache-2.0
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* Version: 1.0.0
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*
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* Interfacing code for the Gamepad Pmod from Psycogenic Technologies,
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* designed for Tiny Tapeout.
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*
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* There are two high-level modules that most users will be interested in:
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* - gamepad_pmod_single: for a single controller;
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* - gamepad_pmod_dual: for two controllers.
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*
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* There are also two lower-level modules that you can use if you want to
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* handle the interfacing yourself:
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* - gamepad_pmod_driver: interfaces with the Pmod and provides the raw data;
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* - gamepad_pmod_decoder: decodes the raw data into button states.
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*
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* The docs, schematics, PCB files, and firmware code for the Gamepad Pmod
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* are available at https://github.com/psychogenic/gamepad-pmod.
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*/
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/**
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* gamepad_pmod_driver -- Serial interface for the Gamepad Pmod.
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*
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* This module reads raw data from the Gamepad Pmod *serially*
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* and stores it in a shift register. When the latch signal is received,
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* the data is transferred into `data_reg` for further processing.
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*
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* Functionality:
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* - Synchronizes the `pmod_data`, `pmod_clk`, and `pmod_latch` signals
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* to the system clock domain.
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* - Captures serial data on each falling edge of `pmod_clk`.
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* - Transfers the shifted data into `data_reg` when `pmod_latch` goes low.
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*
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* Parameters:
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* - `BIT_WIDTH`: Defines the width of `data_reg` (default: 24 bits).
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*
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* Inputs:
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* - `rst_n`: Active-low reset.
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* - `clk`: System clock.
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* - `pmod_data`: Serial data input from the Pmod.
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* - `pmod_clk`: Serial clock from the Pmod.
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* - `pmod_latch`: Latch signal indicating the end of data transmission.
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*
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* Outputs:
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* - `data_reg`: Captured parallel data after shifting is complete.
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*/
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module gamepad_pmod_driver #(
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parameter BIT_WIDTH = 24
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) (
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input wire rst_n,
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input wire clk,
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input wire pmod_data,
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input wire pmod_clk,
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input wire pmod_latch,
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output reg [BIT_WIDTH-1:0] data_reg
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);
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reg pmod_clk_prev;
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reg pmod_latch_prev;
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reg [BIT_WIDTH-1:0] shift_reg;
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// Sync Pmod signals to the clk domain:
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reg [1:0] pmod_data_sync;
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reg [1:0] pmod_clk_sync;
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reg [1:0] pmod_latch_sync;
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always @(posedge clk) begin
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if (~rst_n) begin
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pmod_data_sync <= 2'b0;
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pmod_clk_sync <= 2'b0;
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pmod_latch_sync <= 2'b0;
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end else begin
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pmod_data_sync <= {pmod_data_sync[0], pmod_data};
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pmod_clk_sync <= {pmod_clk_sync[0], pmod_clk};
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pmod_latch_sync <= {pmod_latch_sync[0], pmod_latch};
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end
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end
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always @(posedge clk) begin
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if (~rst_n) begin
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/* Initialize data and shift registers to all 1s so they're detected as "not present".
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* This accounts for cases where we have:
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* - setup for 2 controllers;
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* - only a single controller is connected; and
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* - the driver in those cases only sends bits for a single controller.
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*/
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data_reg <= {BIT_WIDTH{1'b1}};
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shift_reg <= {BIT_WIDTH{1'b1}};
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pmod_clk_prev <= 1'b0;
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pmod_latch_prev <= 1'b0;
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end
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begin
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pmod_clk_prev <= pmod_clk_sync[1];
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pmod_latch_prev <= pmod_latch_sync[1];
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// Capture data on rising edge of pmod_latch:
98+
if (pmod_latch_sync[1] & ~pmod_latch_prev) begin
99+
data_reg <= shift_reg;
100+
end
101+
102+
// Sample data on rising edge of pmod_clk:
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if (pmod_clk_sync[1] & ~pmod_clk_prev) begin
104+
shift_reg <= {shift_reg[BIT_WIDTH-2:0], pmod_data_sync[1]};
105+
end
106+
end
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end
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endmodule
110+
111+
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/**
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* gamepad_pmod_decoder -- Decodes raw data from the Gamepad Pmod.
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*
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* This module takes a 12-bit parallel data register (`data_reg`)
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* and decodes it into individual button states. It also determines
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* whether a controller is connected.
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*
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* Functionality:
120+
* - If `data_reg` contains all `1's` (`0xFFF`), it indicates that no controller is connected.
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* - Otherwise, it extracts individual button states from `data_reg`.
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*
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* Inputs:
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* - `data_reg [11:0]`: Captured button state data from the gamepad.
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*
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* Outputs:
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* - `b, y, select, start, up, down, left, right, a, x, l, r`: Individual button states (`1` = pressed, `0` = released).
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* - `is_present`: Indicates whether a controller is connected (`1` = connected, `0` = not connected).
129+
*/
130+
module gamepad_pmod_decoder (
131+
input wire [11:0] data_reg,
132+
output wire b,
133+
output wire y,
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output wire select,
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output wire start,
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output wire up,
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output wire down,
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output wire left,
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output wire right,
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output wire a,
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output wire x,
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output wire l,
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output wire r,
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output wire is_present
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);
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// When the controller is not connected, the data register will be all 1's
148+
wire reg_empty = (data_reg == 12'hfff);
149+
assign is_present = reg_empty ? 0 : 1'b1;
150+
assign {b, y, select, start, up, down, left, right, a, x, l, r} = reg_empty ? 0 : data_reg;
151+
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endmodule
153+
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/**
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* gamepad_pmod_single -- Main interface for a single Gamepad Pmod controller.
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*
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* This module provides button states for a **single controller**, reducing
159+
* resource usage (fewer flip-flops) compared to a dual-controller version.
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*
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* Inputs:
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* - `pmod_data`, `pmod_clk`, and `pmod_latch` are the signals from the PMOD interface.
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*
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* Outputs:
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* - Each button's state is provided as a single-bit wire (e.g., `start`, `up`, etc.).
166+
* - `is_present` indicates whether the controller is connected (`1` = connected, `0` = not detected).
167+
*/
168+
module gamepad_pmod_single (
169+
input wire rst_n,
170+
input wire clk,
171+
input wire pmod_data,
172+
input wire pmod_clk,
173+
input wire pmod_latch,
174+
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output wire b,
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output wire y,
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output wire select,
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output wire start,
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output wire up,
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output wire down,
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output wire left,
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output wire right,
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output wire a,
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output wire x,
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output wire l,
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output wire r,
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output wire is_present
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);
189+
190+
wire [11:0] gamepad_pmod_data;
191+
192+
gamepad_pmod_driver #(
193+
.BIT_WIDTH(12)
194+
) driver (
195+
.rst_n(rst_n),
196+
.clk(clk),
197+
.pmod_data(pmod_data),
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.pmod_clk(pmod_clk),
199+
.pmod_latch(pmod_latch),
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.data_reg(gamepad_pmod_data)
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);
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gamepad_pmod_decoder decoder (
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.data_reg(gamepad_pmod_data),
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.b(b),
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.y(y),
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.select(select),
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.start(start),
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.up(up),
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.down(down),
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.left(left),
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.right(right),
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.a(a),
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.x(x),
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.l(l),
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.r(r),
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.is_present(is_present)
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);
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endmodule
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/**
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* gamepad_pmod_dual -- Main interface for the Pmod gamepad.
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* This module provides button states for two controllers using
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* 2-bit vectors for each button (e.g., start[1:0], up[1:0], etc.).
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*
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* Each button state is represented as a 2-bit vector:
229+
* - Index 0 corresponds to the first controller (e.g., up[0], y[0], etc.).
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* - Index 1 corresponds to the second controller (e.g., up[1], y[1], etc.).
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*
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* The `is_present` signal indicates whether a controller is connected:
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* - `is_present[0] == 1` when the first controller is connected.
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* - `is_present[1] == 1` when the second controller is connected.
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*
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* Inputs:
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* - `pmod_data`, `pmod_clk`, and `pmod_latch` are the 3 wires coming from the Pmod interface.
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*
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* Outputs:
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* - Button state vectors for each controller.
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* - Presence detection via `is_present`.
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*/
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module gamepad_pmod_dual (
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input wire rst_n,
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input wire clk,
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input wire pmod_data,
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input wire pmod_clk,
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input wire pmod_latch,
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output wire [1:0] b,
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output wire [1:0] y,
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output wire [1:0] select,
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output wire [1:0] start,
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output wire [1:0] up,
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output wire [1:0] down,
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output wire [1:0] left,
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output wire [1:0] right,
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output wire [1:0] a,
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output wire [1:0] x,
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output wire [1:0] l,
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output wire [1:0] r,
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output wire [1:0] is_present
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);
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wire [23:0] gamepad_pmod_data;
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gamepad_pmod_driver driver (
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.rst_n(rst_n),
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.clk(clk),
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.pmod_data(pmod_data),
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.pmod_clk(pmod_clk),
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.pmod_latch(pmod_latch),
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.data_reg(gamepad_pmod_data)
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);
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gamepad_pmod_decoder decoder1 (
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.data_reg(gamepad_pmod_data[11:0]),
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.b(b[0]),
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.y(y[0]),
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.select(select[0]),
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.start(start[0]),
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.up(up[0]),
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.down(down[0]),
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.left(left[0]),
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.right(right[0]),
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.a(a[0]),
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.x(x[0]),
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.l(l[0]),
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.r(r[0]),
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.is_present(is_present[0])
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);
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gamepad_pmod_decoder decoder2 (
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.data_reg(gamepad_pmod_data[23:12]),
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.b(b[1]),
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.y(y[1]),
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.select(select[1]),
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.start(start[1]),
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.up(up[1]),
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.down(down[1]),
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.left(left[1]),
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.right(right[1]),
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.a(a[1]),
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.x(x[1]),
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.l(l[1]),
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.r(r[1]),
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.is_present(is_present[1])
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);
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endmodule

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