NES Emulator (Just a 6502 emulator for now)

A Nintendo Entertainment System (NES) emulator written in C++20. This project aims to emulate the NES hardware, including the CPU and PPU, and provides a graphical debugger for inspection.

Features

Core Components

• CPU (Ricoh 2A03 / 6502):
  • Full implementation of all official 6502 opcodes.
  • Includes support for common unofficial opcodes.
  • Passes the Klaus2m5 functional and interrupt test suites.
• PPU (Picture Processing Unit):
  • OAM DMA transfer is implemented and tested.
  • Scanline and cycle-level timing is in progress.
• Bus:
  • Manages communication between the CPU, PPU, APU, and RAM.
• APU (Audio Processing Unit):
  • Currently a stub.

GUI Debugger (qhex)

The project includes a graphical debugger built with Qt and QHexView, providing:

• A live hexadecimal view of the system memory.
• Real-time display of CPU registers and status flags.
• Controls for step-by-step execution, running, stopping, and resetting the emulation.

Building the Project

Prerequisites

• A C++20 compatible compiler (e.g., GCC, Clang)
• CMake (version 3.15 or later)
• Qt5 (Core, Widgets, Gui)
• Ninja (optional, for faster builds)

Build Steps

# Clone the repository
git clone https://github.com/JuantAldea/NES.git
cd NES

# Configure the build using CMake
mkdir build && cd build
cmake ..
# Or, if you want to use Ninja
cmake .. -G Ninja

# Build the project
cmake --build .

Usage

The build process generates two executables in the build/ directory.

Command-Line (NES)

Not production ready.

GUI Debugger (qhex)

To use the graphical debugger:

./build/qhex

Use the "Load File" button to load a ROM into the emulator's memory at a specified address.

Running Tests

The project uses Google Test for unit testing. The tests are built automatically with the project. To run them, execute the following command from the build directory:

ctest
# Or, if you used Ninja:
ninja test
# Or
make test

Results shall be

[0/1] Running tests...
Test project /tmp/NES/build
    Start 1: testCPU.6502_Klaus2m5_funtional_test
1/3 Test #1: testCPU.6502_Klaus2m5_funtional_test ...   Passed    3.60 sec
    Start 2: testCPU.6502_Klaus2m5_interrupt_test
2/3 Test #2: testCPU.6502_Klaus2m5_interrupt_test ...   Passed    0.00 sec
    Start 3: testDMA.dma_test
3/3 Test #3: testDMA.dma_test .......................   Passed    0.01 sec

100% tests passed, 0 tests failed out of 3

Total Test time (real) =   3.61 sec

License

This project is licensed under the GNU General Public License v2.0. See the LICENSE file for details.