1 files changed, 131 insertions, 0 deletions
diff --git a/home/joypad.asm b/home/joypad.asm
new file mode 100644
index 0000000..ff9e6dc
--- /dev/null
+++ b/home/joypad.asm
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+
+ReadJoypad: ; 0xab8
+; Reads the current state of the joypad and saves the state into
+; some registers the game uses during gameplay. It remembers the joypad state
+; from the current frame, previous frame, and two frames ago.
+	ld a, $20
+	ld [rJOYP], a
+	ld a, [rJOYP]
+	ld a, [rJOYP]
+	and $f
+	swap a
+	ld b, a
+	ld a, $30
+	ld [rJOYP], a
+	ld a, $10
+	ld [rJOYP], a
+	ld a, [rJOYP]
+	ld a, [rJOYP]
+	ld a, [rJOYP]
+	ld a, [rJOYP]
+	ld a, [rJOYP]
+	ld a, [rJOYP]
+	and $f
+	or b
+	cpl  ; a contains currently-pressed buttons
+	ld [hJoypadState], a
+	ld a, $30
+	ld [rJOYP], a
+	ld a, [hJoypadState]
+	ld hl, hPreviousJoypadState
+	xor [hl]  ; a contains buttons that are different from previous frame
+	push af
+	ld hl, hJoypadState
+	and [hl]  ; a contains newly-pressed buttons compared to last frame
+	ld [hNewlyPressedButtons], a
+	ld [hPressedButtons], a
+	pop af
+	ld hl, hPreviousJoypadState
+	and [hl]  ; a contains newly-pressed buttons compared to two frames ago
+	ld [hPrevPreviousJoypadState], a
+	ld a, [hJoypadState]
+	and a
+	jr z, .asm_b15
+	ld hl, hPreviousJoypadState
+	cp [hl]
+	jr nz, .asm_b15
+	; button(s) is pressed, and they're identical to the buttons pressed last frame.
+	; this code is related to holding down a button for an extended period of time.
+	ld hl, hJoyRepeatDelay
+	dec [hl]
+	jr nz, .asm_b1a
+	ld a, [hJoypadState]
+	ld [hPressedButtons], a
+	ld a, [wd807]
+	ld [hJoyRepeatDelay], a
+	jr .asm_b1a
+
+.asm_b15
+	ld a, [wd806]
+	ld [hJoyRepeatDelay], a
+.asm_b1a
+	ld a, [hJoypadState]
+	ld [hPreviousJoypadState], a
+	ld hl, wJoypadStatesPersistent
+	ld a, [hJoypadState]
+	or [hl]
+	ld [hli], a
+	ld a, [hNewlyPressedButtons]
+	or [hl]
+	ld [hli], a
+	ld a, [hPressedButtons]
+	or [hl]
+	ld [hli], a
+	ret
+
+ClearPersistentJoypadStates: ; 0xb2e
+	ld hl, wJoypadStatesPersistent
+	xor a
+	ld [hli], a
+	ld [hli], a
+	ld [hl], a
+	ret
+
+IsKeyPressed2: ; 0xb36
+	ld a, [hJoypadState]
+	and [hl]
+	jr z, .asm_b3e
+	cp [hl]
+	jr z, .asm_b48
+.asm_b3e
+	inc hl
+	ld a, [hJoypadState]
+	and [hl]
+	ret z
+	cp [hl]
+	jr z, .asm_b48
+	xor a
+	ret
+
+.asm_b48
+	ld a, $1
+	and a
+	ret
+
+IsKeyPressed: ; 0xb4c
+; Checks if a key for the specified key config is pressed.
+; input:   hl = pointer to key config byte pair (e.g. wKeyConfigLeftFlipper)
+; output:  zero flag is set if a corresponding key is pressed
+;          zero flag is reset if no corresponding key is pressed
+	ld a, [hJoypadState]
+	and [hl]
+	jr z, .asm_b58
+	cp [hl]
+	jr nz, .asm_b58
+	ld a, [hNewlyPressedButtons]
+	and [hl]
+	ret nz
+.asm_b58
+	inc hl
+	ld a, [hJoypadState]
+	and [hl]
+	ret z
+	cp [hl]
+	jr nz, .asm_b64
+	ld a, [hNewlyPressedButtons]
+	and [hl]
+	ret
+
+.asm_b64
+	xor a
+	ret