From 99922c35f72bd2675ae857e436fe19bca82a48c7 Mon Sep 17 00:00:00 2001
From: Daniel Borges <msk@lywenn.eu.org>
Date: Fri, 4 Jan 2019 16:50:29 +0100
Subject: [PATCH] make nintendo logo fly off like a rocket

---
 Code/main.asm         |   6 +--
 Code/nintendo-out.asm | 106 ++++++++++++++++++++++++++++++++++++++----
 Code/utils.asm        |  17 -------
 Code/utils.inc        |  26 +++++++++++
 rom.gb                | Bin 32768 -> 32768 bytes
 5 files changed, 125 insertions(+), 30 deletions(-)
 create mode 100644 Code/utils.inc

diff --git a/Code/main.asm b/Code/main.asm
index e16a0c2..3857ff7 100644
--- a/Code/main.asm
+++ b/Code/main.asm
@@ -12,11 +12,7 @@ REPT $150 - $104
 ENDR
 
 SECTION "Main", ROM0[$150]
-Start:
-	; shut sound off
-	xor a
-	ld [rNR52], a
-	
+Start:	
 	; enable v-blank interrupt
 	ld a, IEF_VBLANK
 	ld [rIE], a
diff --git a/Code/nintendo-out.asm b/Code/nintendo-out.asm
index b2303bb..a6f5980 100644
--- a/Code/nintendo-out.asm
+++ b/Code/nintendo-out.asm
@@ -1,26 +1,116 @@
 INCLUDE "hardware.inc"
 
-SECTION "NintendoLogo", ROM0
+SECTION "Random", ROM0, ALIGN[4]
+Random:
+	db -1, 1, 2, -1, 4, 3, -2, -1, -4, 3, -1, 5, 2
+RandomEnd:
+
+HaltAndClearIF: MACRO
+	halt
+	xor a
+	ld [rIF], a
+ENDM
 
 EXPORT ScrollNintendoOut
 SECTION "Scroll Nintendo Out", ROM0
 ScrollNintendoOut:
-	ld b, 30
+
+	; wait a moment
+	ld b, 32
 .wait
-	halt
-	xor a
-	ld [rIF], a
+	HaltAndClearIF
 	dec b
 	jr nz, .wait
+	
+	; sound ON
+	ld a, $80
+	ldh [rNR52], a ; sound ON with noise channel
+	ld a, $77
+	ldh [rNR50], a ; max volume on both speakers
+	ld a, $88
+	ldh [rNR51], a ; noise channel on both speakers
+
+	; make noise
+	ld a, 0
+	ldh [rNR41], a ; set sound duration
+	ld a, $F0
+	ldh [rNR42], a ; set volume
+	ld a, $72
+	ldh [rNR43], a ; set frequency
+	ld a, $80
+	ldh [rNR44], a ; turn on
+
+	; nudge nintendo logo
+	ld d, HIGH(Random)
+	ld e, 0
+	ld b, 42
+.noise
+	HaltAndClearIF
+	HaltAndClearIF
+	ld a, [de]
+	ldh [rSCY], a
+	
+	inc e
+	ld a, e
+	cp a, RandomEnd - Random
+	jr nz, .next
+	ld e, 0
+.next
+
+	ld a, [de]
+	ldh [rSCX], a
+
+	inc e
+	ld a, e
+	cp a, RandomEnd - Random
+	jr nz, .next2
+	ld e, 0
+.next2
+	
+	dec b
+	jr nz, .noise
 
-.scrollup
-	halt
 	xor a
-	ld [rIF], a
+	ldh [rSCY], a
+	
+	; change noise
+	ld a, $62
+	ldh [rNR43], a ; set frequency
+	
+	ld b, 4 ; number of frames before reducing volume
+	ld c, 16 ; number of steps before volume is 0
+
+	; nintendo logo lift-off!
+.scrollup
+	HaltAndClearIF
+	; scroll up
 	ldh a, [rSCY]
 	inc a
 	ldh [rSCY], a
+	
+	; fade out
+	ld a, c
+	or a
+	jr z, .novolumechange
+	dec b
+	jr nz, .novolumechange
+	; decrement volume by 1
+	; see http://gbdev.gg8.se/wiki/articles/Gameboy_sound_hardware obscure behavior...
+	ld a, $08
+REPT 15 
+	ldh [rNR42], a
+ENDR
+	ld b, 4
+	dec c
+	
+.novolumechange
+	; loop until nintendo logo is out of screen
+	ldh a, [rSCY]
 	cp a, 88
 	jp nz, .scrollup
 	
+	; sound off
+	xor a
+	ldh [rNR52], a
+	
 	ret
\ No newline at end of file
diff --git a/Code/utils.asm b/Code/utils.asm
index 85e16d0..9eb80b6 100644
--- a/Code/utils.asm
+++ b/Code/utils.asm
@@ -28,20 +28,3 @@ MemorySet:
 	or c
 	jr nz, MemorySet
 	ret
-
-	; \1: sprite ID
-	; \2: X position
-	; \3: Y position
-	; \4: tile number
-	; \5: flags
-SetSprite: MACRO
-	ld hl, _OAMRAM + \1 * 4
-	ld a, \3
-	ld [hl+], a
-	ld a, \2
-	ld [hl+], a
-	ld a, \4
-	ld [hl+], a
-	ld a, \5
-	ld [hl+], a
-ENDM
diff --git a/Code/utils.inc b/Code/utils.inc
new file mode 100644
index 0000000..63b6586
--- /dev/null
+++ b/Code/utils.inc
@@ -0,0 +1,26 @@
+INCLUDE "hardware.inc"
+
+	; destroys A
+ClearAndEnableInterrupts: MACRO
+	xor a
+	ei ; will take effect AFTER next instruction
+	ldh a, [rIF]
+ENDM
+
+	; \1: sprite ID
+	; \2: X position
+	; \3: Y position
+	; \4: tile number
+	; \5: flags
+	; destroys A and HL
+SetSprite: MACRO
+	ld hl, _OAMRAM + \1 * 4
+	ld a, \3
+	ld [hl+], a
+	ld a, \2
+	ld [hl+], a
+	ld a, \4
+	ld [hl+], a
+	ld a, \5
+	ld [hl+], a
+ENDM
\ No newline at end of file
diff --git a/rom.gb b/rom.gb
index cea432a74a869d206baf57c9afc7f4a0af1cd0c2..de1b9c6c94c319cae5889a9e216226ec6c7ac3df 100644
GIT binary patch
delta 442
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zz<=^X!}b$p3=%&+pR7{iuGpyX^W;Q_HclxeVG!rX$;pL0hLafm>KT~9Iv((!?dB_E
zSpUGm?#TmpMTQB2*}RMbjAxHAC^9q%R`W3mFo4<r#26SCFr2jjs&szfq{uKsOpuX*
z1ISloI3UQ(!<Yfma&`@a9mfMlyM_l2XJr}A?qNKu$8dHM!{N1zVhkVJ(?4|NuXpET
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jRZs?cNf8}NAq%jv@P2Um7jft*-}(n?CpS;zyHfxFSCpgI

delta 299
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z=s|-W<AeX}e?Q<q$p8Wq9onQmG;BXn#vt+Iq?D2{cg049A1AAnK=jX(6E7-EV)Uy&
zy?gxwHL$)1{AUFiKqfobJ$c}+$S^@LkC#z^@$7j9MTQ2!IzC1L1~B`d7z5)1hO;+-
zDxDuVDKg9u6J%uI0P+<X4hXXGFlK<XoL$3U$ML|?uHk{hSuKXM`x(z3V>mmB;qV4V
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