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render mode 4 w/ page flipping, stub green swap

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This commit is contained in:
Matthew Berry 2020-10-15 23:47:58 -07:00
parent e1f348ac1c
commit 337e7d0bc8
2 changed files with 22 additions and 11 deletions
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2
src/crab/gba.cr
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@ -30,7 +30,7 @@ class GBA
end
def handle_events : Nil
@scheduler.schedule PPU::REFRESH, ->handle_events
@scheduler.schedule 280896, ->handle_events
while event = SDL::Event.poll
case event
when SDL::Event::Quit then exit 0

31
src/crab/ppu.cr
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@ -1,13 +1,4 @@
class PPU
# Display timings in cycles
HDRAW = 960
HBLANK = 272
SCANLINE = HDRAW + HBLANK
VDRAW = 160 * SCANLINE
VBLANK = 68 * SCANLINE
REFRESH = VDRAW + VBLANK
# LCD Control
class DISPCNT < BitField(UInt16)
bool obj_window_display
bool window_1_display
@ -47,6 +38,8 @@ class PPU
num priority, 2
end
@framebuffer : Bytes = Bytes.new 0x12C00 # framebuffer as 16-bit xBBBBBGGGGGRRRRR
getter pram = Bytes.new 0x400
getter vram = Bytes.new 0x18000
@ -81,7 +74,7 @@ class PPU
elsif @vcount == 160
@dispstat.vblank = true
@gba.scheduler.schedule 0, ->start_vblank_line
@gba.display.draw @vram
draw
elsif @vcount >= 160
@gba.scheduler.schedule 0, ->start_vblank_line
else
@ -93,10 +86,28 @@ class PPU
@gba.scheduler.schedule 960, ->start_hblank
end
def draw : Nil
case @dispcnt.bg_mode
when 3
@gba.display.draw @vram
when 4
base = @dispcnt.display_frame_select ? 0xA000 : 0
(240 * 160).times do |idx|
pal_idx = @vram[base + idx]
@framebuffer[idx * 2] = @pram[pal_idx * 2]
@framebuffer[idx * 2 + 1] = @pram[pal_idx * 2 + 1]
end
@gba.display.draw @framebuffer
else abort "Unsupported background mode: #{@dispcnt.bg_mode}"
end
end
def read_io(io_addr : Int) : Byte
case io_addr
when 0x000 then 0xFF_u8 & @dispcnt.value
when 0x001 then 0xFF_u8 & @dispcnt.value >> 8
when 0x002 then 0xFF_u8 # todo green swap
when 0x003 then 0xFF_u8 # todo green swap
when 0x004 then 0xFF_u8 & @dispstat.value
when 0x005 then 0xFF_u8 & @dispstat.value >> 8
when 0x006 then 0xFF_u8 & @vcount