Search found 12 matches

by MegaBoyEXE
Thu Jan 18, 2018 9:54 pm
Forum: GBDev
Topic: Blank main menu in Spot (that 7up game) [Solved]
Replies: 6
Views: 4639

Re: Blank main menu in Spot (that 7up game) [Solved]

In GBE+ this was never true because VBlank fires instantly (no 4 cycle delay). When reading LY into A, it never picked up a value of 0x90. But if there is a 4 cycle delay, sometimes this loop manages to read LY right before VBlank triggers an IRQ. Registers A and F get pushed and popped to the stac...
by MegaBoyEXE
Thu Jan 18, 2018 6:25 pm
Forum: GBDev
Topic: Blank main menu in Spot (that 7up game) [Solved]
Replies: 6
Views: 4639

Re: Blank main menu in Spot (that 7up game)

How many freaking "Spot" games did they think we needed in the 90s? I've never seen a carbonated beverage with that many games :P Anyway, the 3rd "Spot" game is in fact still broken in GBE+. I'll investigate what's going on. Didn't knew there were more of them. The one I'm talking about is the "ROM...
by MegaBoyEXE
Wed Jan 17, 2018 10:30 pm
Forum: GBDev
Topic: Blank main menu in Spot (that 7up game) [Solved]
Replies: 6
Views: 4639

Blank main menu in Spot (that 7up game) [Solved]

I was testing some games in my emu, and found a weird issue with that 7Up game named Spot. After the scrolling text in title scene, the screen goes blank and a little hand sprite is suposed to appears after a very short wait time, followed by remaining graphics in Main Menu. In my emulator the scree...
by MegaBoyEXE
Sun Jan 14, 2018 1:32 pm
Forum: GBDev
Topic: DMG Sound Implementation - Kind of working but broken
Replies: 13
Views: 5521

Re: DMG Sound Implementation - Kind of working but broken

The APU has too many quirks that are hard to follow and implement. I would recommend you to start with a simpler channel, like channel 2 or 3. Channel 3 is quite simple, just update pos in waveform table and outputs the shifted volume. Channel 2 is also simple, just need volume envelope implementati...
by MegaBoyEXE
Sun Jan 14, 2018 1:14 pm
Forum: GBDev
Topic: DMG Sound Implementation - Kind of working but broken
Replies: 13
Views: 5521

Re: DMG Sound Implementation - Kind of working but broken

I'm implementing my emulator in C# too, currently inside Unity3D, but the core code is separated from Unity3D dependency and can converted to a lib. I'm trying to document most of my findings on APU and all channels, and I can now pass almost all tests from dmg_sound tests, missing a few details wit...
by MegaBoyEXE
Mon Jan 08, 2018 4:29 pm
Forum: GBDev
Topic: Channel 4 sounding louder than expected
Replies: 7
Views: 4623

Re: Channel 4 sounding louder than expected

I understood now! Instead of sampling a specific point in the 524 KHz wave (when downsampling to 96 KHz), I need to sample a bigger interval of it, which I will get the average as a sample. I just changed my code, and it worked pretty well! I'm sorry I did not get this earlier. It's pretty clear now...
by MegaBoyEXE
Mon Jan 08, 2018 2:42 pm
Forum: GBDev
Topic: Channel 4 sounding louder than expected
Replies: 7
Views: 4623

Re: Channel 4 sounding louder than expected

You're decimating before you filter. That doesn't work: that has already aliased the high frequencies down in, and by filtering after the fact you just make the channel sound muddy always. Oh, ok maybe I did not fully understood the concept. Let me try to explain with some pseudo-code. Here's the A...
by MegaBoyEXE
Mon Jan 08, 2018 12:58 pm
Forum: GBDev
Topic: Channel 4 sounding louder than expected
Replies: 7
Views: 4623

Re: Channel 4 sounding louder than expected

So, it really needs a filter. I was not expecting entering at this topic yet, as it was my first time doing procedural audio programming. I'm still in learn process about everything related to sound programming. I tried applying this "filter" only to channel 4, as others sounds good already. Tried a...
by MegaBoyEXE
Mon Jan 08, 2018 9:13 am
Forum: GBDev
Topic: Channel 4 sounding louder than expected
Replies: 7
Views: 4623

Channel 4 sounding louder than expected

Hello, I've got the sound emulation working and all channels sounds good. I know I'm missing a lot of the "obscure behaviors" from the guides, but it works better than I expected. Problem is: Channel 4 is generating a "buzz" effect that sounds louder than it should be. The effect of the "ocean waves...
by MegaBoyEXE
Sat Jul 08, 2017 3:45 pm
Forum: GBDev
Topic: Requirements for running blarggh's tests
Replies: 3
Views: 2468

Re: Requirements for running blarggh's tests

Found the big culprist while writing unit tests for instructions! I was tricked by the mnemonic of instruction "JP (HL)", that actually does PC = HL, and I was doing PC = mem[HL]. I look to myself, and feel pretty dumb now :oops: . 1. Why would I load to PC a 8-bit value???? 2. Didn't I noticed that...
by MegaBoyEXE
Wed Jul 05, 2017 1:25 pm
Forum: GBDev
Topic: Requirements for running blarggh's tests
Replies: 3
Views: 2468

Re: Requirements for running blarggh's tests

Thank you for your reply! I'm following your progress with bar code emulation and RE! Wishes good luck on that! It's pretty inspiring seeing people today still trying to everything available for GB being properly emulatated! Now about your comments, a simple command line log for CPU state was one of...
by MegaBoyEXE
Tue Jul 04, 2017 10:40 am
Forum: GBDev
Topic: Requirements for running blarggh's tests
Replies: 3
Views: 2468

Requirements for running blarggh's tests

Hello, I've started my adventures in emulation a few days ago. I still didn't finished implementing all instructions and almost didn't touched PPU stuff yet. The implemented instructions are enough to get blarggh's tests start running. But it seems it entered a loop before even starting doing actual...