Add the sound/beep.s example

This is the most simple example you can come up when it comes to
producing sound on the NES/Famicom. Basically, a single note is
delivered to the APU which is continuously on.

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>

3 files changed, 12 insertions, 2 deletions

diff --git a/scroll/include/all.s b/scroll/include/all.s
index 763feb4..e9f059d 100644
--- a/scroll/include/all.s
+++ b/scroll/include/all.s
@@ -6,7 +6,6 @@
 .include "ppu.s"
 .include "../../shared/asm.s"
 .include "../../shared/joypad.s"
-.include "../../shared/ppu.s"
 
 .include "reset.s"
 .include "palettes.s"
diff --git a/scroll/include/ppu.s b/scroll/include/ppu.s
index 34410a0..f62d702 100644
--- a/scroll/include/ppu.s
+++ b/scroll/include/ppu.s
@@ -1,3 +1,15 @@
+;; WRITE_PPU_DATA is a macro that will write into PPUADDR the given address and
+;; into PPUDATA the given byte value.
+.macro WRITE_PPU_DATA address, value
+    bit $2002
+    lda #.HIBYTE(address)
+    sta $2006
+    lda #.LOBYTE(address)
+    sta $2006
+    lda #value
+    sta $2007
+.endmacro
+
 .scope PPU
     CONTROL = $2000
     MASK    = $2001
diff --git a/scroll/toggle.s b/scroll/toggle.s
index 57f403f..bba0e97 100644
--- a/scroll/toggle.s
+++ b/scroll/toggle.s
@@ -31,7 +31,6 @@
 .include "./include/ppu.s"
 .include "./include/oam.s"
 .include "./include/globals.s"
-.include "../shared/ppu.s"
 .include "../shared/clear.s"
 
 ;; Variables used on this example.