Implemented better game loop and shadow OAM/DMA

game/game.asm

@@ -1,23 +1,39 @@
 INCLUDE "game/text.asm"
 INCLUDE "game/controller.asm"
 
+; Shadow OAM, allows us to have a shadow copy of all sprites for
+; editing whenever we want
+SECTION "ram_shadowoam", WRAM0,ALIGN[8]
+shadow_oam:
+  ds 160
+shadow_oam_inuse:
+  ds 1
+
 SECTION "Game Loop", ROM0
 
 GameLoop:
-    ld de, HelloWorldStr
+    ld de, FirstCutScene
     call StartText
-.mainloop
-    ; Start our game loop
-    call UpdateController
-    call DrawActiveText
+.mainloop ; Our main game loop
+    call UpdateController ; Update our controller
+
+    ; Reset our oam sprites in use
+    xor a
+    ld [shadow_oam_inuse], a
+
+    ; Call sprite handlers
+
+    ; Call other handlers
     call WaitVBlank
+    call DrawActiveText
+    call RunDMA
     jr .mainloop
 
 Section "Hello wrold string", ROM0
 
-HelloWorldStr:
+FirstCutScene:
     ;  [                  ]
     db "...wake up...\n"
-    db "please wake up...#"
+    db "please wake up...", "#"
     db "...we don't have\n"
     db "time, wake up...", 0

game/text.asm

@@ -114,7 +114,6 @@ StartText:
     ret
 
 ; Draw text if one is currently active
-; @return a - 0 if not active, 1 if active
 DrawActiveText:
     ld a, [textwriter_active] ; Check if text is currently active
     and a

main.asm

@@ -64,26 +64,20 @@ Start:
     ld a, SCRN_Y
     ld [rWY], a
 
-    ; Reset OAM memory with zeros
-    ld hl, _OAMRAM ; Set position of OAM Ram to hl
-    ld a, 0 ; Fill that memory space with zero
-    ld b, $FEA0 - _OAMRAM ; Get the full size of the fill
-    call Memfill
-
-    ; Reset WRAM memory with zeros
-    ld hl, _RAM ; Set position of OAM Ram to hl
-    ld a, $01 ; Fill that memory space with zero
-    ld bc, $E000 - _RAM ; Get the full size of the fill
-    call Memfill16
-    ld hl, _RAM ; Set position of OAM Ram to hl
-    ld a, $00 ; Fill that memory space with zero
-    ld bc, $E000 - _RAM ; Get the full size of the fill
-    call Memfill16
-
     ; Initialize other stuff
+    call InitTools
     call InitController
     call InitWindow
 
+    ; Reset OAM memory with zeros
+    ; First reset our shadow OAM
+    ld hl, shadow_oam ; Set position of OAM Ram to hl
+    ld a, 0 ; Fill that memory space with zero
+    ld b, shadow_oam_inuse - shadow_oam ; Get the full size of the fill
+    call Memfill
+    ; Then call our OAM guy
+    call RunDMA
+
     ; Turn the screen on, display background
     ld a, LCDCF_ON|LCDCF_BGON|LCDCF_WINON|LCDCF_WIN9C00
     ld [rLCDC], a ; Set the screen flags

test.map

@@ -21,45 +21,51 @@ ROM Bank #0 (HOME):
            $0029 = UpdateController.onenibble
            $0009 = UpdateController
            $0000 = InitController
-  SECTION: $0166-$0176 ($0011 bytes) ["Game Loop"]
-           $016C = GameLoop.mainloop
-           $0166 = GameLoop
-  SECTION: $00BB-$00FC ($0042 bytes) ["Hello wrold string"]
-           $00BB = HelloWorldStr
-  SECTION: $0150-$0165 ($0016 bytes) ["Tools"]
-           $0159 = Memfill
-           $0163 = WaitVBlank
-           $0150 = Memcpy
-           $0159 = Memfill.repeatFill
-           $015E = Memfill16.repeatFill
-           $015E = Memfill16
+  SECTION: $017D-$0194 ($0018 bytes) ["Game Loop"]
+           $0183 = GameLoop.mainloop
+           $017D = GameLoop
+  SECTION: $00AB-$00EC ($0042 bytes) ["Hello wrold string"]
+           $00AB = FirstCutScene
+  SECTION: $0150-$017C ($002D bytes) ["Tools"]
+           $0166 = Memfill
+           $0170 = WaitVBlank
+           $0173 = dma_routine_start
+           $017D = dma_routine_end
+           $015D = Memcpy
+           $0166 = Memfill.repeatFill
+           $016B = Memfill16.repeatFill
+           $0179 = dma_routine_start.loop
+           $0150 = InitTools
   SECTION: $0040-$0040 ($0001 bytes) ["InterruptVblank"]
   SECTION: $0048-$0048 ($0001 bytes) ["InterruptLCDC"]
   SECTION: $0050-$0050 ($0001 bytes) ["InterruptTimer_Overflow"]
   SECTION: $0058-$0058 ($0001 bytes) ["InterruptSerial"]
   SECTION: $0060-$0060 ($0001 bytes) ["Interruptp1thru4"]
   SECTION: $0100-$014F ($0050 bytes) ["Header"]
-  SECTION: $0061-$00BA ($005A bytes) ["Intro code"]
+  SECTION: $0061-$00AA ($004A bytes) ["Intro code"]
            $0061 = Start
   SECTION: $0280-$127F ($1000 bytes) ["Font"]
            $0280 = Page1
            $1280 = Page1End
-    SLACK: $2CC3 bytes
+    SLACK: $2CB5 bytes
 
 WRAM Bank #0:
-  SECTION: $C000-$C008 ($0009 bytes) ["ram_textwriter"]
-           $C002 = textwriter_posx
-           $C003 = textwriter_posy
-           $C007 = textwriter_ending
-           $C008 = textwriter_pausing
-           $C005 = textwriter_active
-           $C004 = textwriter_curdelay
-           $C006 = textwriter_starting
-           $C000 = textwriter_curtext
-  SECTION: $C009-$C00A ($0002 bytes) ["ram_controller"]
-           $C00A = controller_newkeys
-           $C009 = controller_curkeys
-    SLACK: $0FF5 bytes
+  SECTION: $C0A1-$C0A9 ($0009 bytes) ["ram_textwriter"]
+           $C0A3 = textwriter_posx
+           $C0A4 = textwriter_posy
+           $C0A8 = textwriter_ending
+           $C0A9 = textwriter_pausing
+           $C0A6 = textwriter_active
+           $C0A5 = textwriter_curdelay
+           $C0A7 = textwriter_starting
+           $C0A1 = textwriter_curtext
+  SECTION: $C0AA-$C0AB ($0002 bytes) ["ram_controller"]
+           $C0AB = controller_newkeys
+           $C0AA = controller_curkeys
+  SECTION: $C000-$C0A0 ($00A1 bytes) ["ram_shadowoam"]
+           $C0A0 = shadow_oam_inuse
+           $C000 = shadow_oam
+    SLACK: $0F54 bytes
 
 WRAM Bank #1:
   EMPTY
@@ -92,7 +98,9 @@ OAM:
   EMPTY
 
 HRAM:
-  EMPTY
+  SECTION: $FF80-$FF8A ($000B bytes) ["hram_tools"]
+           $FF80 = RunDMA
+    SLACK: $0074 bytes
 
 SRAM Bank #0:
   EMPTY

test.sym

@@ -19,25 +19,31 @@
 00:0029 UpdateController.onenibble
 00:0009 UpdateController
 00:0000 InitController
-00:016C GameLoop.mainloop
-00:0166 GameLoop
-00:00BB HelloWorldStr
-00:0159 Memfill
-00:0163 WaitVBlank
-00:0150 Memcpy
-00:0159 Memfill.repeatFill
-00:015E Memfill16.repeatFill
-00:015E Memfill16
+00:0183 GameLoop.mainloop
+00:017D GameLoop
+00:00AB FirstCutScene
+00:0166 Memfill
+00:0170 WaitVBlank
+00:0173 dma_routine_start
+00:017D dma_routine_end
+00:015D Memcpy
+00:0166 Memfill.repeatFill
+00:016B Memfill16.repeatFill
+00:0179 dma_routine_start.loop
+00:0150 InitTools
 00:0061 Start
 00:0280 Page1
 00:1280 Page1End
-00:C002 textwriter_posx
-00:C003 textwriter_posy
-00:C007 textwriter_ending
-00:C008 textwriter_pausing
-00:C005 textwriter_active
-00:C004 textwriter_curdelay
-00:C006 textwriter_starting
-00:C000 textwriter_curtext
-00:C00A controller_newkeys
-00:C009 controller_curkeys
+00:C0A3 textwriter_posx
+00:C0A4 textwriter_posy
+00:C0A8 textwriter_ending
+00:C0A9 textwriter_pausing
+00:C0A6 textwriter_active
+00:C0A5 textwriter_curdelay
+00:C0A7 textwriter_starting
+00:C0A1 textwriter_curtext
+00:C0AB controller_newkeys
+00:C0AA controller_curkeys
+00:C0A0 shadow_oam_inuse
+00:C000 shadow_oam
+00:FF80 RunDMA

tools.asm

@@ -1,5 +1,20 @@
+; Like the NES and Super NES, DMA on the Game Boy takes access to RAM
+; and ROM away from the CPU.  But unlike those two, the CPU continues
+; to run.  So store a tiny subroutine in HRAM (tightly coupled
+; memory) to keep the CPU busy until OAM DMA is done.
+SECTION "hram_tools", HRAM
+RunDMA: ds 11
+
 SECTION "Tools", ROM0
 
+InitTools:
+    ; Copy the sprite DMA routine
+    ld de, dma_routine_start
+    ld hl, RunDMA
+    ld bc, dma_routine_end - dma_routine_start
+    call Memcpy
+    ret
+
 ; Memory copier
 ; @param de - Address source to start of data to be copied
 ; @param hl - Address destomatopm where to copy the data to
@@ -60,3 +75,15 @@ WaitVBlank:
 .wait
     halt
     ret
+
+;;
+; The routine gets copied to high RAM
+dma_routine_start:
+  ld a,shadow_oam >> 8
+  ld [rDMA],a
+  ld a,40
+.loop:
+  dec a
+  jr nz,.loop
+  ret
+dma_routine_end: