Create readjoypad.asm

1 files changed, 31 insertions, 0 deletions

diff --git a/engine/readjoypad.asm b/engine/readjoypad.asm
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index 00000000..96897455
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+++ b/engine/readjoypad.asm
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+ReadJoypad_:: ; c000 (3:4000)
+; Poll joypad input.
+; Unlike the hardware register, button
+; presses are indicated by a set bit.
+
+	ld a, 1 << 5 ; select direction keys
+	ld c, 0
+
+	ld [rJOYP], a
+	rept 6
+	ld a, [rJOYP]
+	endr
+	cpl
+	and %1111
+	swap a
+	ld b, a
+
+	ld a, 1 << 4 ; select button keys
+	ld [rJOYP], a
+	rept 10
+	ld a, [rJOYP]
+	endr
+	cpl
+	and %1111
+	or b
+
+	ld [hJoyInput], a
+
+	ld a, 1 << 4 + 1 << 5 ; deselect keys
+	ld [rJOYP], a
+	ret