I saw your project on the changelog weekly newsletter and wanted to try it out. But now I have no idea how to start. I downloaded retroarch but there's no cli coming with it. Can you flesh this out in your documentation?

When the sweep is disabled, but the negate flag is set (%00001000 written to $4001), the frequency_generator_output() function shouldn't be called. In fact, because the last 3 bits are set to 0, the adjust_period_based_on_frequency_generator() function doesn't end up calling it.

But, it's being called to check if the square channel should be silenced: !self.enabled || self.period < 8 || self.length_counter == 0 || self.frequency_generator_output() >= 0x7FF

When frequency_generator_output() is called here (with the sweep disabled), self.period is shifted by 0 bits, so period_delta = self.period. Thus self.period.wrapping_sub( period_delta ).wrapping_sub( 1 ) = (0-1), underflowing to 0xFFFF which is indeed greater than 0x7FF. So the channel is silenced.

Added an additional check to see if the sweep is enabled before checking its state.

The noise channel is silent any time the envelope decay bit (i.e. bit 4 of $400C) is set to 0.

When bit 4 is 0, the envelope decay is disabled, so is_manually_controlled is set to false, and thus the volume of the noise channel gets set to self.generated_volume in VolumeGenerator's volume() function. The problem is, self.generated_volume is never updated, and so it stays at the default volume of 0, silencing the channel.

As far as I can tell, the noise channel is supposed to work exactly the same as the square channels when it comes to the volume register (apart from duty bits), so my proposed fix is to duplicate the function used to update the square channels' volume generator, and update the noise channel along with the squares in clock_sequencer().

I tried to play the demo NES game from NESMaker trollburner_demo.nes.zip but it fails saying

Unable to load ROM - unhandled mapper: 30

Sorry about that! Maybe try another ROM?

It would be amazing if this emulator could run NESMaker games! http://austinmckinley.com/8bit/the-tools.html

I wanted to poke at pinky-web on my own machine, so I cloned master and followed the native WebAssembly backend instructions in the Readme. The exact nightly I downloaded was rustc 1.25.0-nightly (616b66dca 2018-02-02).

The local server started up just fine, but if I go to localhost:8000 in a browser that ran the version at http://koute.github.io/pinky-web/ without problems, then I see the description on the left as expected, but on the right I see just "Loading..." instead of the ROM selection menu.

If I open the console on the local version, I see only the single line

Finished loading Rust wasm module 'pinky_web'

instead of the two lines

WebGL support using context: webgl
Finished loading Rust wasm module 'pinky_web'

I see at http://koute.github.io/pinky-web/ .

So I suppose something is going wrong with the wasm loading somehow?

• macOS, issue exists on Firefox and Chrome (at least)
• go to http://koute.github.io/pinky-web/
• Click "Load your own ROM"
• Try to load any file
• See in Javascript console: TypeError: $1.files is not a function

This addresses cases where WebGL is either broken or disabled. The error message on Chrome was a Cannot read property 'create'Shader' of null TypeError, however, the cause of this error was the variable gl being null after attempting to retrieve all valid WebGL rendering contexts.

I noticed SQ_1 was not playing in the roms I tested (using RetroArch). I narrowed it down to virtual_apu.rs, line 577: self.period.wrapping_sub( period_delta ).wrapping_sub( 1 )

That .wrapping_sub( 1 ) is the problem. If I change it to 0, or change it to .wrapping_add( 1 ), it seems to work fine. ~~I'd make a pull request, but I'm honestly not sure what that subtraction is there for, so I don't know if/how it should be changed.~~

Edit: After reading over the APU doc again, I see that the subtraction is to account for the difference in SQ_1's sweep. Still not sure why a wrapping_sub there seems to silence the channel though. I can wrapping_add any number without a problem.

Perhaps the easiest way to pump up the number of games you can (legally) offer through the demo would be to add support for the Action 53 mapper (iNES mapper 28). This mapper is about as complex as MMC1 (iNES mapper 1) and makes the emulator compatible with Action 53 Volume 4, which contains over 50 homebrew games.

A on the left and B on the right is backward from how many NES games map their controls. Affects Lode Runner, Championship Lode Runner, and Thwaite. (I was lead programmer for Thwaite.)

Audio is a pop-fest, as if random values were written to $4011 several times per second, and games play too slow. This is in Firefox 72.0.2 (64-bit) on Xubuntu 18.04 on a Dell Inspiron 11-3168 laptop with a quad-core Pentium N3710 CPU, running on AC power.

"Unable to load ROM - unhandled mapper: 34"

Lack of BNROM support affects Deadly Towers, Haunted: Halloween '85, Lizard, and 240p Test Suite (BNROM version) (pinobatch/240p-test-mini). I was lead developer on HH85 and 240p and can help explain the mapper if you need.