The chip-8 from thefarwind

Pull memory out into separate struct

change crate name from 'chip-8' to 'chip8'

I want to change the name, so the module is 'chip8' rather than 'chip_8'. I know it can be done, but haven't managed to get it working yet.

Feature:Implement instruction 0x0NNN -- call RCA 1802 program at address NNN

This is a rarely used function whose implementation I've had a little difficulty looking up. Nevertheless, it needs to be implemented eventually.

Move ncurses io elements to separate file, and actually use.

Currently there are prototyped ncurses elements just kinda sitting out there in the code that A: should be separated nicely from main and B: should be used.

#15 Display
#13 Keypad
#11 Audio

Crash: Games crash when attempting to draw a sprite offscreen

According to the spec, this shouldn't cause the game to crash. Games, such as pong, use this feature when wrapping a paddle from top to bottom of the screen.

Turn display into a trait

Currently the ncurses library is baked into the Chip8 struct, rather than being an implementation detail that main is using.

Turn audio into trait

Currently the Audio struct directly references ncurses code. This issue is to create an implementable trait for Audio that chip8 uses.

bit shift instructions (8xy6,8xye) poorly handle x=0xF case

Currently, 0xF case turns into bad values for both of these instructions, because it sets VF to the overflow/underflow, and then shifts that value left or right.

Instead, this (undefined) behavior should follow the pattern set by the other overflow/underflow operations, which is do the operation to VX, then set VF to the overflow/underflow.

Move ownership of memory and io to a bus struct

Move display tracking into memory

chip 8 is meant to have the display info in memory. This PCR is to make the emulator closer match the intended situation.

draw flag not set with 00e0

draw flag should be set when 00e0 is called.

this was uncovered by a unit test :D

Implement io as traits rather than references to ncurses io structs

This issue will be complete when the following issues are closed out:

Add project description to README

there is currently no real description of this project or it's purpose. Add these details to the readme.

Move registers into memory

looking at a magazine post about chip8 from way back in the day, it appears that the registers were originally intended to reside in memory. They should be moved there.

Opcode 0xFX0A does not increment to the next instruction

Most opcodes increment the pc by a value of two when read. 0xFX0A is supposed to increment to the next instruction -- however, it fails to do so.

opcode 9XY0 is broken -- sets wrong pc value

instead of skipping if VX != VY, it sets the program counter equal to 2 or 4, which is a major bug.

Move ncurses screen to ncurses io structs

Currently, the chip8 machine/processor is passing the screen to each ncurses io object when a method using the screen is called. This should be changed so that each object has a reference to the screen, and the machine/processor has no knowledge of the ncurses library.

Move stack into memory

The stack was designed to live in the memory. this issue is to make the emulator more closely match that design.

Make tests reproducible

Currently, tests heavliy make use of the rand crate. While this is nice for just general checking, if a test fails the test should be reproducible. Therefore, the seed should either be A) Set before hand or B) recorded if an error occurs, and have the random seed be settable.

I would strongly prefer to implement method B.

Controls input is wonky when running pong.

Testing with pong, the wrong key causes the paddles to move up, and there is no key that causes the paddle to move down.

Change Mock{Input, Display, Audio} to Fake{Input,Display,Audio}

Seems like using the word fake is more common than mock. Not sure if this will be implemented or declined.

Set up missing crates/cargo configuration

there are missing options for crates/cargo setup. Part of this issue will be looking up the necessary settings and setting them.

Add build details to README

there are currently no details on how to build and run debug, build and run release, and run the tests. These should be added to the read me.

Create a debugger

this would allow the user to debug programs written for chip-8 to determine what is occuring.

change '4' for displayed character to a solid block

Currently, pixels which are 'on' are displayed as a 4 using ncursesio. this should be changed to a solid block.

Add code comments

None of the functions, structs, etc in the code have any code comments on them. Code comments should be added so that the code has documentation.

Pull Chip8 struct out into separate module

this issue is to pull the chip8 logic out into a separate module.

synchronize emulation with the host system.

running chip-8 unsyncronized seems to work fine, but for larger emulators, they will need to be synchronized with the host system to work properly.

Therefore, it should be implemented here.

Tests are all broken

When switching chip8 such that the audio, display, and input are all fed to a new function, all the tests were broken. This is blocked until after audio, display, and input are implemented as traits (see #20).

Turn project into a library

Currently this is only usable with main.rs. There should be a lib file as well, which main.rs imports.

Implement mock io devices to use for testing

The test module will have a set of mock io devices to create the chip8 machine and tests inputs and outputs.

Move ncuses display out into separate ncuses io module.

This is part of #7. This covers the display logic.

change optcode to opcode

opcode is short for operational code. change any mention of optcode to opcode.

Turn input into a trait

Currently ncurses library is pretty hard-baked into the chip-8 device. It should be pulled out such that it's an implementation detail.

change index values when used in instructions

when the index is used by instructions, the index is meant to be incremented over the course of the instructions. This behaviour should be implemented.

Pull Processor out of Chip8

this issue is to separate the processor from the rest of the chip 8 machine

Tests: Implement remaining instruction tests

There's a lot of code for testing which remains unimplemented. This code needs fleshed out.

move desired configuration values to a config file

Currently all values are hardcoded. Several of these should be specified in a config file.

move tests to separate file

Currently the tests module is sitting inside of main.rs. This should be moved to a separate file called tests.rs

Move audio to separate struct

Move audio out of main.rs and into a separate struct.

VF records overflow of I + VX > 0xFFFF, not I +VX > 0xFFF

Necessary clarifcation before implementation -- VX + I > 0xFFF -> I > 0xFFF or I = VX + I - 0xFFF?

Move input key logic for ncurses interface into ncurses module

This is part of issue #7. This handles moving the input ncurses keypad logic into another module.

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