Yet Another CHIP-8 Virtual Machine and Interpreter.

CHIP-8 is both a simple interpreted programming language and a specification for a virtual machine. It's also a good place to start experimenting with emulation.

Dependencies

This implementation uses SDL2 for rendering and input. Both Rust and SDL2 are cross-platform so the emulator should be as well. I won't cover SDL2 installation here but you will need it available when you build the executable.

Building and Running

Since this is a Rust project, we proceed with cargo. That is, in the root directory run cargo build --release. This will give you an executable in target/release named yac8. Run it with a program file as the argument to fire up the machine. You can also combine the build and run process using cargo run if you feel like it.

yac8 supports variable clock frequencies (defaults to 700hz), verbose logging of instructions to the terminal, and a scan mode that parses and prints a program's instructions without executing. The executable has --help, so check it out. The variable clock frequency is useful because Chip-8 doesn't actually specify a clock speed for instruction execution, only timer countdown rates (60hz). Programs work best with a variety of clock speeds.

Note that yac8 doesn't yet support sound. Programs are rendered to 10x the original resolution of 64 by 32 and this is not currently configurable. Controls are mapped as below and are also not currently configurable.

your keyboard    Chip-8 hexpad input
  1 2 3 4      |      1 2 3 C
  Q W E R      |      4 5 6 D
  A S D F      |      7 8 9 E
  Z X C V      |      A 0 B F

TODO:

• Add some visual examples

• Implement audio facilities

• Configurable keymapping

• A user interface and stepping mode for debugging.

  Lay out the instructions and opcodes as a navigable interface, dump the registers in a corner, and allow stepping through arbitrary numbers of instructions. I think I'd like this to be a terminal user interface, using something like tui-rs.