Use DMA OAM transfer to write entities to OAM

4 files changed, 96 insertions, 57 deletions

diff --git a/definitions.gbasm b/definitions.gbasm
index 84e7691..7ac2721 100644
--- a/definitions.gbasm
+++ b/definitions.gbasm
@@ -37,6 +37,7 @@
 
 .DEFINE next_free_head_higher_bytes $c7
 .DEFINE mem_next_free_head_lower_bytes ($c6ff)
+
 .DEFINE mem_dungeon_generation_heads $c700 ; Takes the memory from c700 to c717
 ; struct head {
 ; 	direction: u8 (really u3 but padding),
@@ -63,15 +64,36 @@
 ; 	_padding: u24
 ; }
 
-.DEFINE mem_entites_list $c980 ; Until IDK WHERE
+.DEFINE mem_entites_list $c980 ; Until c9ff
 ; struct entity {
 ;	sprite: u8,
 ;	x: u8,
 ;	y: u8,
 ;	direction: u8 (bit 3 = is_moving, bit 2-0: direction),
+;	ai_function_pointer: 16
+;	_padding: u16
 ; }
 
+.DEFINE mem_oam_buffer $ca00 ; Until $ca9f
+.DEFINE mem_oam_buffer_high $ca
+
 .DEFINE enum_direction_left $01
 .DEFINE enum_direction_right $02
 .DEFINE enum_direction_up $03
 .DEFINE enum_direction_down $04
+
+
+; HIGH_RAM:
+;
+; 80-85 ; Free to use as temporary variables
+.DEFINE tmp_var_1 ($80)
+.DEFINE tmp_var_2 ($81)
+.DEFINE tmp_var_3 ($82)
+.DEFINE tmp_var_4 ($83)
+.DEFINE tmp_var_5 ($84)
+.DEFINE tmp_var_6 ($85)
+
+; 86-90 ; OAM_DMA_Transfer_routine
+.DEFINE OAM_DMA_Transfer_routine $ff86
+
+; 90-fe ; Stack
diff --git a/entities.gbasm b/entities.gbasm
index 1e4772f..03786d9 100644
--- a/entities.gbasm
+++ b/entities.gbasm
@@ -1,12 +1,12 @@
-Display_Entities:
+Prepare_Entities:
 	LD A, $00
-	LD ($80), A
+	LD $tmp_var_1, A
 	LD HL, $mem_entites_list
-	CALL =Display_Entity
-	CALL =Display_Entity
+	CALL =Prepare_Entity
+	CALL =Prepare_Entity
 	RET
 
-Display_Entity:
+Prepare_Entity:
 	LD A, (HL+)
 	LD E, A
 
@@ -17,10 +17,10 @@ Display_Entity:
 	LD B, A
 	SUB $83
 	CP D
-	JP NC, =Display_Entity.skip
+	JP NC, =Prepare_Entity.skip
 	ADD $10
 	CP D
-	JP C, =Display_Entity.skip
+	JP C, =Prepare_Entity.skip
 	LD A, D
 	SUB $80
 	SUB B
@@ -35,10 +35,10 @@ Display_Entity:
 	LD C, A
 	SUB $83
 	CP D
-	JP NC, =Display_Entity.skip
+	JP NC, =Prepare_Entity.skip
 	ADD $10
 	CP D
-	JP C, =Display_Entity.skip
+	JP C, =Prepare_Entity.skip
 	LD A, D
 	SUB $80
 	SUB C
@@ -50,16 +50,16 @@ Display_Entity:
 
 	LD A, $mem_bunny_direction
 	BIT 3, A
-	JR Z, =Display_Entity.Viewport_offset_end
+	JR Z, =Prepare_Entity.Viewport_offset_end
 	AND $07
 	CP $enum_direction_down
-	JR Z, =Display_Entity.Viewport_offset_down
+	JR Z, =Prepare_Entity.Viewport_offset_down
 	CP $enum_direction_right
-	JR Z, =Display_Entity.Viewport_offset_right
+	JR Z, =Prepare_Entity.Viewport_offset_right
 	CP $enum_direction_up
-	JR Z, =Display_Entity.Viewport_offset_up
+	JR Z, =Prepare_Entity.Viewport_offset_up
 
-	Display_Entity.Viewport_offset_left: 
+	Prepare_Entity.Viewport_offset_left:
 		LD A, $reg_viewport_x
 		SUB $08
 		AND $0f
@@ -68,9 +68,9 @@ Display_Entity:
 		ADD B
 
 		LD B, A
-		JR =Display_Entity.Viewport_offset_end
+		JR =Prepare_Entity.Viewport_offset_end
 
-	Display_Entity.Viewport_offset_right: 
+	Prepare_Entity.Viewport_offset_right:
 		LD A, $reg_viewport_x
 		SUB $08
 		AND $0f
@@ -79,9 +79,9 @@ Display_Entity:
 
 		LD B, A
 
-		JR =Display_Entity.Viewport_offset_end
+		JR =Prepare_Entity.Viewport_offset_end
 
-	Display_Entity.Viewport_offset_up: 
+	Prepare_Entity.Viewport_offset_up:
 		LD A, $reg_viewport_y
 		SUB $08
 		AND $0f
@@ -91,9 +91,9 @@ Display_Entity:
 
 		LD C, A
 
-		JR =Display_Entity.Viewport_offset_end
+		JR =Prepare_Entity.Viewport_offset_end
 
-	Display_Entity.Viewport_offset_down: 
+	Prepare_Entity.Viewport_offset_down:
 		LD A, $reg_viewport_y
 		SUB $08
 		AND $0f
@@ -102,74 +102,74 @@ Display_Entity:
 
 		LD C, A
 
-	Display_Entity.Viewport_offset_end: 
+	Prepare_Entity.Viewport_offset_end:
 
 	LD A, (HL+)
 	BIT 3, A
 	LD D, A
 	LD A, $00
-	JR Z, =Display_Entity.Not_Moving_Animation
+	JR Z, =Prepare_Entity.Not_Moving_Animation
 
 	LD A, D
 	AND $07
 
 	CP $enum_direction_down
-	JR Z, =Display_Entity.moving_offset_down
+	JR Z, =Prepare_Entity.moving_offset_down
 	CP $enum_direction_right
-	JR Z, =Display_Entity.moving_offset_right
+	JR Z, =Prepare_Entity.moving_offset_right
 	CP $enum_direction_up
-	JR Z, =Display_Entity.moving_offset_up
+	JR Z, =Prepare_Entity.moving_offset_up
 
-	Display_Entity.moving_offset_left: 
+	Prepare_Entity.moving_offset_left:
 		LD A, $mem_moving_animation_step
 		XOR $ff
 		ADD B
 		LD B, A
 
-		JR =Display_Entity.moving_offset_end
+		JR =Prepare_Entity.moving_offset_end
 
-	Display_Entity.moving_offset_right: 
+	Prepare_Entity.moving_offset_right:
 		LD A, $mem_moving_animation_step
 		INC A
 		ADD B
 		LD B, A
 
-		JR =Display_Entity.moving_offset_end
+		JR =Prepare_Entity.moving_offset_end
 
-	Display_Entity.moving_offset_up: 
+	Prepare_Entity.moving_offset_up:
 		LD A, $mem_moving_animation_step
 		XOR $ff
 		ADD C
 		LD C, A
 
-		JR =Display_Entity.moving_offset_end
+		JR =Prepare_Entity.moving_offset_end
 
-	Display_Entity.moving_offset_down: 
+	Prepare_Entity.moving_offset_down:
 		LD A, $mem_moving_animation_step
 		INC A
 		ADD C
 		LD C, A
 
-	Display_Entity.moving_offset_end: 
+	Prepare_Entity.moving_offset_end:
 
 
 	LD A, $mem_moving_animation_step
-	Display_Entity.Not_Moving_Animation:
+	Prepare_Entity.Not_Moving_Animation:
 
 	SUB $08
 	BIT 7, A
-	JR Z, =Display_Entity.Hop_ABS1_end
+	JR Z, =Prepare_Entity.Hop_ABS1_end
 
 	; Adding hop animation to Y
 	XOR $ff
 	INC A
-	Display_Entity.Hop_ABS1_end:
+	Prepare_Entity.Hop_ABS1_end:
 	SUB $04
 	BIT 7, A
-	JR Z, =Display_Entity.Hop_ABS2_end
+	JR Z, =Prepare_Entity.Hop_ABS2_end
 	XOR $ff
 	INC A
-	Display_Entity.Hop_ABS2_end:
+	Prepare_Entity.Hop_ABS2_end:
 	ADD C
 
 	LD C, A
@@ -178,43 +178,43 @@ Display_Entity:
 	AND $07
 
 	CP $enum_direction_left
-	JR Z, =Display_Entity.Left_Direction_sprite
+	JR Z, =Prepare_Entity.Left_Direction_sprite
 	CP $enum_direction_right
-	JR Z, =Display_Entity.Right_Direction_sprite
+	JR Z, =Prepare_Entity.Right_Direction_sprite
 	CP $enum_direction_up
-	JR Z, =Display_Entity.Up_Direction_sprite
-	JP =Display_Entity.Down_Direction_sprite
+	JR Z, =Prepare_Entity.Up_Direction_sprite
+	JP =Prepare_Entity.Down_Direction_sprite
 
-	Display_Entity.Left_Direction_sprite:
+	Prepare_Entity.Left_Direction_sprite:
 		LD D, $00
-		JP =Display_Entity.Write_OBJ
+		JP =Prepare_Entity.Write_OBJ
 
-	Display_Entity.Right_Direction_sprite:
+	Prepare_Entity.Right_Direction_sprite:
 		LD A, $02
 		ADD E
 		LD E, A
 		LD D, $20
-		JP =Display_Entity.Write_OBJ
+		JP =Prepare_Entity.Write_OBJ
 
-	Display_Entity.Up_Direction_sprite:
+	Prepare_Entity.Up_Direction_sprite:
 		LD A, $04
 		ADD E
 		LD E, A
 		LD D, $00
-		JP =Display_Entity.Write_OBJ
+		JP =Prepare_Entity.Write_OBJ
 
-	Display_Entity.Down_Direction_sprite:
+	Prepare_Entity.Down_Direction_sprite:
 		LD A, $08
 		ADD E
 		LD E, A
 		LD D, $00
-		JP =Display_Entity.Write_OBJ
+		JP =Prepare_Entity.Write_OBJ
 
-	Display_Entity.Write_OBJ:
+	Prepare_Entity.Write_OBJ:
 	PUSH HL
 	; First OBJ (left)
-	LD H, $FE
-	LD A, ($80)
+	LD HL, $mem_oam_buffer
+	LD A, $tmp_var_1
 	LD L, A
 	LD A, C
 	LD (HL+), A
@@ -242,8 +242,8 @@ Display_Entity:
 	LD A, D
 	LD (HL+), A
 	LD A, L
-	LD ($80), A
+	LD $tmp_var_1, A
 	POP HL
 
-	Display_Entity.skip:
+	Prepare_Entity.skip:
 	RET
diff --git a/init.gbasm b/init.gbasm
index ec41320..8898848 100644
--- a/init.gbasm
+++ b/init.gbasm
@@ -60,4 +60,20 @@ Empty_VRAM: ; (Clear screen)
 	LD A, $01
 	LD $reg_interrupt_enable, A
 
+Copy_OAM_DMA_Transfer_Routine_To_HRAM:
+	LD HL, $OAM_DMA_Transfer_routine
+	LD DE, =OAM_DMA_Transfer_routine_src
+	LD BC, $000a
+	CALL =memcpy
+
 	JP =Entrypoint
+
+OAM_DMA_Transfer_routine_src:
+	LD A, $mem_oam_buffer_high
+	LD ($46), A
+	LD A, $28        ; delay for a total of 4×40 = 160 M-cycles
+	OAM_DMA_Transfer_routine_src.wait:
+	    DEC A						             ; 1 M-cycle
+	    JR NZ, =OAM_DMA_Transfer_routine_src.wait    ; 3 M-cycles
+	    RET
+	OAM_DMA_Transfer_routine_src.end:
diff --git a/main.gbasm b/main.gbasm
index ad1fa44..eb1ea52 100644
--- a/main.gbasm
+++ b/main.gbasm
@@ -24,7 +24,7 @@ New_Dungeon:
 VBLANK_Entrypoint:
 	CALL =Display_Prepared_Block
 	CALL =Display_Object
-	CALL =Display_Entities
+	CALL $OAM_DMA_Transfer_routine
 
 	CALL =Object_Interactions_Check
 
@@ -32,6 +32,7 @@ VBLANK_Entrypoint:
 	CALL =Move_Bunny
 
 	CALL =Prepare_Scrolling_Map
+	CALL =Prepare_Entities
 	RET
 
 .INCLUDE "tiles.gbasm"