slides.txt

         FPGABoy by Kai Tamkun
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       Image Credit: Joan Stark
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                Project

 - Made a Game Boy sound chip

 - Accuracy nice but not a requirement
   - Clocks and CDC are finicky

 - Got bored, implemented NES APU too
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    Pokmon Card GB2 (GR duel music)
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   The Legend of Zelda (title screen)
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               Generators

 - Created some nice generators
   (TableGen, TriangleGen, NoiseGen,
   FPSummer, DynamicClocker, Divider)
   and proceeded to never use them

 - Used SquareGenExternal, StaticClocker
   and PeriodClocker in APUs

 - Used some generators for the graphics

 - Can very conveniently prefill Vecs
   with sine wave values
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               Interfaces

 - Standard buttons, switches and LEDs

 - Code produces 9-bit audio

 - Audio is output over HDMI and aux
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        Incremental Development

  1. Implemented square and sine waves
  2. Multi-cycle channel mixer
  3. Top-level Verilog
  4. Basic audio over aux
  5. VGM tools
  6. State machine
  7. Game Boy channels: 1, 2, 4, 3
  8. HDMI output: video, audio
  9. Presentation slides
 10. NES channels: 1, 2, 3, 4
 11. Silly graphics stuff
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                Testing

 - Testing? Never heard of it #yolo

 - test:main ratio < 20%

 - Tests mostly just generate VCD output
   for manual inspection in GTKWave

 - Divider was exhaustively tested for
   8-bit inputs
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             Inner Workings

 - State machine writes to registers,
   channel modules read and interpret

 - State machine input stored in BRAM
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              Presentation

 - I forgot there were two projectors 


 - Slides stored as ASCII(-ish) in BRAM

 - Rendered by FPGA
   - okLch to RGB conversion by lookup
     table

 - Typeface might look familiar

 - Why not use an NES controller too?
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              Game Boy APU

 - Game Boy and Game Boy Color use the
   same sound chip

 - Channel 1: square wave with frequency
   sweeper, envelope, length counter and
   duty cycler

 - Channel 2: channel 1 without sweeper

 - Channel 3: output arbitrary waveforms
   from registers

 - Channel 4: LFSR-based noise generator
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                NES APU

 - Similar to Game Boy APU

 - Channels: 2 square waves, triangle
   wave, noise, delta modulation channel

 - DMC unimplemented due to format
   constraints
   - Not very commonly used anyway

 - Triggering based on register writes,
   not designated bits
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               Conclusion

 - 171+ hours well spent

 - Definitely avoid using 6+ different
   clocks if you can
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     Thanks for a great quarter! =)


     Repo @ https://heimskr.gay/apu


         Discord: Heimskr#0001