79 lines
1.2 KiB
NASM
79 lines
1.2 KiB
NASM
INCLUDE "hardware.inc"
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EXPORT JoypadDown, JoypadPressed
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Section "Joypad memory", HRAM
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; Bits 0..7 are A, B, Select, Start, Right, Left, Up, Down
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JoypadPressed: ds 1
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JoypadNewlyPressed: ds 1
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JoypadDown: ds 1
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EXPORT InitJoypad
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SECTION "Init joypad", ROM0
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InitJoypad:
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xor a
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ldh [JoypadDown], a
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ldh [JoypadPressed], a
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ldh [JoypadNewlyPressed], a
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ret
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EXPORT ReadJoypad
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SECTION "Read Joypad", ROM0
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ReadJoypad:
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; read directions
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ld a, P1F_5
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ldh [rP1], a
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ldh a, [rP1]
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ldh a, [rP1]
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ldh a, [rP1]
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ldh a, [rP1]
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and a, $0F
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swap a ; move into high nibble
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ld b, a
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; read buttons
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ld a, P1F_4
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ldh [rP1], a
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ldh a, [rP1]
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ldh a, [rP1]
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ldh a, [rP1]
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ldh a, [rP1]
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and a, $0F
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; merge directions and buttons
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; complement so that active buttons read as 1
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or a, b
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cpl
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; add to currently pressed buttons
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ld b, a
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ldh a, [JoypadNewlyPressed]
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or a, b
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ldh [JoypadNewlyPressed], a
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; reset joypad
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ld a, $30
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ldh [rP1], a
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ret
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EXPORT UpdateJoypad
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SECTION "Update joypad", ROM0
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UpdateJoypad:
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; compute & store just pressed buttons
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ldh a, [JoypadNewlyPressed]
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ld b, a
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ldh a, [JoypadPressed]
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cpl
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and a, b
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ldh [JoypadDown], a
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; update pressed
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ld a, b
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ldh [JoypadPressed], a
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; reset newly pressed
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xor a
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ldh [JoypadNewlyPressed], a
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ret
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