Hack is the name of the educational computer system developed by Noam Nisan and Shimon Schocken for the book The Elements of Computing Systems and the Nand2Tetris online course. More information about the course and accompanying text (which describes the Hack machine) can be found at http://www.nand2tetris.org/.
This project is an experiment in embedded systems programming. Well, if the Nintendo DS comes under that classification. (There doesn't appear to be an agreed upon definition of "embedded".) I set myself the challenge of emulating the Hack machine on an NDS to see how much performance I could get out of it.
This software is published under the MIT licence (see LICENCE).
You will need either a physical NDS and means of launching unsigned code on it, or an NDS emulator, in order to run the Hack emulator. If you want to run the emulator in an emulator, I recommend DeSmuME.
You will need the devkitPro + devkitARM + libnds toolchain for Nintendo DS homebrew development in order to build this project. Installation instructions can be found at https://devkitpro.org/wiki/Getting_Started.
Currently the emulator will run a single program linked into the final executable, as this makes it easy to test with an NDS emulator. Once you have a program in .hack format (text encoded binary), follow the steps below to build the .nds executable:
-
Compile
util/packcd util make pack -
Convert your ROM (text encoded binary, 16 bits per line) to little-endian 16-bit raw binary
util/pack < <rom_file> > data/rom.bin
-
Build the Hack Emulator, linking the binary file
make
The included data/rom.bin is a simple program that draws stripes on the screen.
This is a work in progress. Currently it simply interprets the binary bit by bit, but I hope to implement JIT binary translation (to 32-bit ARM machine code) later.
As the Hack display is twice the width of one of the NDS', I use subpixel rendering to approximate a 2x2 pixel region of the Hack display in one real pixel. Since the Hack display is 1bpp black and white, there are 16 possible underlying patterns, so I have used a 16 colour precomputed subpixel palette. The dots of the NDS display are arranged in the order Blue, Green, Red, from left to right, within each pixel, which may be different from your display's arrangement if you are running it in an emulator, in which case edges will tend to look fuzzy (and colourful).
Currently only the left and right D-pad buttons are mapped, to the left and right arrow keys. I intend to map the other buttons and implement a touch screen keyboard later.