Lay out a proper structure for the project

Let's divide things by topic instead of a broad "examples" directory.
This will allow for simple files to co-exist together with full-blown
projects.

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

4 files changed, 109 insertions, 0 deletions

diff --git a/space/include/apu.s b/space/include/apu.s
new file mode 100644
index 0000000..32ccff2
--- /dev/null
+++ b/space/include/apu.s
@@ -0,0 +1,6 @@
+.segment "CODE"
+
+.scope APU
+    DMC           = $4010
+    FRAME_COUNTER = $4017
+.endscope
diff --git a/space/include/joypad.s b/space/include/joypad.s
new file mode 100644
index 0000000..8711c28
--- /dev/null
+++ b/space/include/joypad.s
@@ -0,0 +1,63 @@
+.segment "CODE"
+
+;;;
+;; Joypad controller code. The following memory addresses are reserved: $21-$23.
+;;
+;; Memory address $21 is used for internal purposes, whereas $22 and $23 contain
+;; the bitmask of the buttons that are pressed from each controller.
+;;;
+
+.scope Joypad
+    ;; Button masks.
+    BUTTON_A      = 1 << 7
+    BUTTON_B      = 1 << 6
+    BUTTON_SELECT = 1 << 5
+    BUTTON_START  = 1 << 4
+    BUTTON_UP     = 1 << 3
+    BUTTON_DOWN   = 1 << 2
+    BUTTON_LEFT   = 1 << 1
+    BUTTON_RIGHT  = 1 << 0
+
+    ;; Port addresses for controllers.
+    JOYPAD1 = $4016
+    JOYPAD2 = $4017
+
+    ;; We keep all the information from controller from mainly two variables:
+    ;; m_buttons1 and m_buttons2; containing respectively the buttons pressed
+    ;; for this frame for both controllers. The m_inv_buttons ($21) is an
+    ;; internal variable and should not be used for anything outside of this
+    ;; usage.
+    m_inv_buttons = $21
+    m_buttons1    = $22
+    m_buttons2    = $23
+
+    ;; READ_CONTROLLER reads the input from the controller mapped into the given
+    ;; port, and saves the state into the given `buttons` address.
+    ;; Implementation taken from NESHacker's example of smb3-like movement.
+    .macro READ_CONTROLLER port, buttons
+        lda m_inv_buttons
+        tay
+        lda #1
+        sta port
+        sta m_inv_buttons
+        lsr
+        sta port
+    :
+        lda port
+        lsr
+        rol m_inv_buttons
+        bcc :-
+        tya
+        eor m_inv_buttons
+        and m_inv_buttons
+        sta buttons
+    .endmacro
+
+    ;; read sets the values for m_buttons1 and m_buttons2 as read from both
+    ;; controllers.
+    .proc read
+        READ_CONTROLLER JOYPAD1, m_buttons1
+        READ_CONTROLLER JOYPAD2, m_buttons2
+        rts
+    .endproc
+.endscope
diff --git a/space/include/oam.s b/space/include/oam.s
new file mode 100644
index 0000000..ecd1b7d
--- /dev/null
+++ b/space/include/oam.s
@@ -0,0 +1,13 @@
+.segment "CODE"
+
+.scope OAM
+    ADDR = $2003
+    DMA  = $4014
+.endscope
+
+.macro OAM_WRITE_SPRITES
+    lda #$00
+    sta OAM::ADDR
+    lda #$02
+    sta OAM::DMA
+.endmacro
diff --git a/space/include/ppu.s b/space/include/ppu.s
new file mode 100644
index 0000000..23fd978
--- /dev/null
+++ b/space/include/ppu.s
@@ -0,0 +1,27 @@
+.segment "CODE"
+
+.scope PPU
+    CONTROL = $2000
+    MASK    = $2001
+    STATUS  = $2002
+    SCROLL  = $2005
+    ADDRESS = $2006
+    DATA    = $2007
+.endscope
+
+.macro PPU_ADDR address
+    lda #.HIBYTE(address)
+    sta PPU::ADDRESS
+    lda #.LOBYTE(address)
+    sta PPU::ADDRESS
+.endmacro
+
+;; WRITE_PPU_DATA is a macro that will write into PPU::ADDRESS the given address
+;; and into PPU::DATA the given byte value.
+.macro WRITE_PPU_DATA address, value
+    bit PPU::STATUS
+
+    PPU_ADDR address
+    lda #value
+    sta PPU::DATA
+.endmacro