A Simple FPGA Implementation of the Nintendo Entertainment System
VHDL Verilog Python Other
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APU
Coregen
HDMI
NES_2A03
PPU
TestBenches
ac97
doc
roms
synaesthesia
tools
.project
CartridgeROM.vhd
CartridgeROM_Coregen.vhd
ColorPalette.vhd
Genesys_NES.vhd
NES_Mainboard.vhd
NES_Pack.vhd
README.md
nes_top.ucf

README.md

NESFPGA

This project implements a simplified version of the Nintendo Entertainment System on an FPGA, that can execute Super Mario Bros.

Getting Started

I used the Digilent Genesys FPGA board, which is currently the only board this project works on. Sadly, you will need a version of Xilinx ISE software to synthesize this project. I used version 14.5, the free Webpack Edition should be fine.

Create a new project, and first include the top module Genesys_NES.vhd, to see what other files are missing. Don't forget the constraints file nes_top.ucf. Then add every .vhd and .v file, except the TestBenches, and CartridgeROM*.vhd

Cartridge

CartridgeROM.vhd reads the ROM data from .dat files in the directory roms/. The default filenames are 'roms/smb_chr.dat' and 'roms/smb_prg.dat'. These files are already shipped with the project, but you can generate them with tools/romconv.py. Beware, this project only supports 32 KiB ROMs.

XST should support the ROM inferrence style in CartridgeROM.vhd, but this is rather slow. For faster synthesis, use CartridgeROM_Coregen.vhd and include the appropriate .ngc files from the Coregen directory. This directory also includes the Coregen project files, and romconv.py can be modified to generate the necessary .coe files from .nes ROMs.

MyHDL Part

Since the APU is programmed in MyHDL, it needs to be converted to VHDL or Verilog code for synthesis. apu_convert.py does this for you, but you will need to install MyHDL (at least version 0.7). Alternatively, for synthesis you can just use the pregenerated file APU/APU_Main.v.

Directory Overview

NES_2A03 - The modified CPU from Dan Leach's NES-On-a-FPGA project PPU - Implementation of the NES 2C02 APU - MyHDL code and testbench for the APU

TestBenches - Various VHDL based testbenches tools - Tools for generating ROM helper files, and framebuffer viewer roms - ROM files in .nes and converted form

HDMI - Chrontel CH7301C interface from xps_tft ac97 - The 3rd party AC97 module with my wrapper

synaesthesia - First attempt at a ISE-independent build system... Ignore for now

Flashing the FPGA board

To persistently save the bistream on the FPGA boards flash RAM, you need to use Xilinx iMPact. These are the settings i used to generate the MCS file:

  • Parallel BPI Single Boot
  • Virtex 5 / 32M
  • 16 bit width
  • 28F256P30 (not 512, the genesys schematic is lying)

Testbenches

NES_Framebuffer_TB.vhd

This is the testbench for simulating everything down from NES_Mainboard. But beware, you will need a fast and expensive simulator for this to be useful.

It writes the framebuffer data to fbdump_top.out. The FBView tool in tools/fbview can be used to view this file. It includes a build script, but you will need a working gcc and the SDL library to compile it.

The testbench also includes a primitive way for simulating controller pad inputs in the process CONTROLLER_INPUT. It uses 1 for not pressed and 0 for pressed. From left to right, the button mapping is "Right, Left, Down, Up, Start, Select, B, A"

apu_tb.py

Unlike the other testbenches, this is found in the APU directory. To use it, you will need Py65. Use these commands to get and configure python to find it:

$ cd APU $ git clone https://github.com/mnaberez/py65 $ export PYTHONPATH=py65

To start simulating the first song of the SMB nsf, use this command:

$ python apu_tb.py smb.nsf 0

It will write the file smb-0.wav to the output directory.

I recommend you to acquire a recent version of PyPy, and use it instead of standard CPython, as it speeds up the simulation by orders of magnitude