From 1d1f08646352df00977a88adb99e04d54e4dfd5d Mon Sep 17 00:00:00 2001 From: Miquel Sabaté Solà Date: Tue, 2 Apr 2024 22:02:59 +0200 Subject: basics: Add a flickering example MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add an example on how to flicker sprites so to not surpass the scanline limit for them. Signed-off-by: Miquel Sabaté Solà --- shared/diskun.s | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ shared/joypad.s | 56 ++++++++++++++++++++++++++++++++++ 2 files changed, 151 insertions(+) create mode 100644 shared/diskun.s create mode 100644 shared/joypad.s (limited to 'shared') diff --git a/shared/diskun.s b/shared/diskun.s new file mode 100644 index 0000000..d8bab90 --- /dev/null +++ b/shared/diskun.s @@ -0,0 +1,95 @@ +;;; Simple sprite that can be moved with the dpad easily. Use it to have +;;; something funny moving. + +.include "joypad.s" + +.scope Diskun + m_screen_x = $30 + m_screen_y = $31 + + .proc init_palettes + lda #$3F + sta $2006 ; PPUADDR + lda #$00 + sta $2006 ; PPUADDR + + ldx #0 + @load_palettes_loop: + lda palettes, x + sta $2007 ; PPUDATA + inx + cpx #$20 + bne @load_palettes_loop + rts + palettes: + DEFAULT_COLOR = $11 + + ;; Background + .byte DEFAULT_COLOR, $36, $17, $0F + .byte DEFAULT_COLOR, $00, $00, $00 + .byte DEFAULT_COLOR, $00, $00, $00 + .byte DEFAULT_COLOR, $00, $00, $00 + + ;; Foreground + .byte DEFAULT_COLOR, $28, $0F, $30 + .byte DEFAULT_COLOR, $00, $00, $00 + .byte DEFAULT_COLOR, $00, $00, $00 + .byte DEFAULT_COLOR, $00, $00, $00 + + rts + .endproc + + .proc update + lda #Joypad::BUTTON_UP + and Joypad::m_buttons1 + beq @check_down + + dec Diskun::m_screen_y + dec Diskun::m_screen_y + jmp @check_left + @check_down: + lda #Joypad::BUTTON_DOWN + and Joypad::m_buttons1 + beq @check_left + + inc Diskun::m_screen_y + inc Diskun::m_screen_y + @check_left: + lda #Joypad::BUTTON_LEFT + and Joypad::m_buttons1 + beq @check_right + + dec Diskun::m_screen_x + dec Diskun::m_screen_x + @check_right: + lda #Joypad::BUTTON_RIGHT + and Joypad::m_buttons1 + beq @end + + inc Diskun::m_screen_x + inc Diskun::m_screen_x + @end: + rts + .endproc + + .proc nmi_update + lda Diskun::m_screen_x + sta $203 + sta $20B + clc + adc #8 + sta $207 + sta $20F + + lda Diskun::m_screen_y + sta $200 + sta $204 + clc + adc #8 + sta $208 + sta $20C + + rts + .endproc +.endscope + diff --git a/shared/joypad.s b/shared/joypad.s new file mode 100644 index 0000000..2abf959 --- /dev/null +++ b/shared/joypad.s @@ -0,0 +1,56 @@ +;;; TODO: safe read + +.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 -- cgit v1.2.3