nesdev.com

;Nes Gamepad demo program 4/28/08
;-------------------

; INES header setup


   .inesprg 1
   .ineschr 0   ; zero because we don't have character data
   .inesmir 1
   .inesmap 0 

   .bank 1
   .org $FFFA
   .dw 0       ; NMI routine
   .dw start    ; Reset routine
   .dw 0           ; IRQ routine

   .bank 0
   .org $8000

start:

key_a      EQU   %00000001 ; A button press
key_b      EQU    %00000010 ; B
key_select     EQU    %00000100 ; select
key_start     EQU    %00001000 ; start
key_up     EQU    %00010000 ; up arrow
key_down     EQU    %00100000 ; down
key_left     EQU    %01000000 ; left arrow
key_right     EQU    %10000000 ; right


ab_pressed   EQU   %00000011 ; A and B are pressed
         
button_state    EQU     $00
button_state2   EQU   $0F


    sei        ; ignore IRQs
    cld        ; disable decimal mode
    ldx #$40
    stx $4017  ; disable APU frame IRQ
    ldx #$ff
    txs        ; Set up stack
    inx        ; now X = 0
    stx $2000  ; disable NMI
    stx $2001  ; disable rendering
    stx $4010  ; disable DMC IRQs

vblankwait1: 
    bit $2002
    bpl vblankwait1

    ; We now have about 30,000 cycles to burn before the PPU stabilizes.
    ; Use it to clear RAM.  X is still 0...
    txa
clrmem:      ; this is for the video stuff
    sta $000,x
    sta $100,x
    sta $200,x
    sta $300,x
    sta $400,x
    sta $500,x
    sta $600,x
    sta $700,x  ; Remove this if you're storing reset-persistent data
    inx
    bne clrmem
   
vblankwait2:
    bit $2002
    bpl vblankwait2


; *** CLEAR SOUND REGISTERS ***
   

   lda #$00      ; clear all the sound registers by setting
   ldx #$00      ; everything to 0 in the Clear_Sound loop
Clear_Sound:
   sta $4000,x      ; store accumulator at $4000 offset by x
   inx         ; increment x
   cpx #$0F      ; compare x to $0F
   bne Clear_Sound      ; branch back to Clear_Sound if x != $0F

   lda #$10      ; load accumulator with $10
   sta $4010      ; store accumulator in $4010
   lda #$00      ; load accumulator with 0
   sta $4011      ; clear these 3 registers that are
   sta $4012      ; associated with the delta modulation
   sta $4013      ; channel of the NES



loop:
   jsr updatejoy

   ;Check the state of the right key
   lda button_state
   and #key_right
   beq right_not_pressed
   jsr right_is_pressed


right_not_pressed:
   
   ;Check the state of the left button
   lda button_state
   and #key_left
   beq left_not_pressed
   jsr left_is_pressed

left_not_pressed:

   ;Check the state of the up arrow
   lda button_state
   and #key_up
   beq up_not_pressed
   jsr up_is_pressed

up_not_pressed:

   ;Check the state of the downss arrow
   lda button_state
   and #key_down
   beq down_not_pressed
   jsr down_is_pressed

down_not_pressed:


   ;Check if A and B are pressed
   lda button_state

   AND #$03  ; mask out A+B bits
   CMP #$03  ; see if it equals A+B
   BNE ab_not_pressed
   
   jsr ab_is_pressed

ab_not_pressed:

   ;Check if A is pressed
   lda button_state
   AND #key_a  ; mask out bits
   BEQ a_not_pressed
   jsr a_is_pressed

a_not_pressed:

   ;Check if b button is pressed
   lda button_state
   and #key_b
   beq b_not_pressed
   jsr b_is_pressed

b_not_pressed:   


   ;Check if select button is pressed
   lda button_state
   and #key_select
   beq select_not_pressed
   jsr select_is_pressed


select_not_pressed:



   ;Check if start button is pressed
   lda button_state
   and #key_start
   beq start_not_pressed
   jsr start_is_pressed


start_not_pressed:



  ;Check State of Right Button of Joypad #2
   lda button_state2
   and #key_right
   beq right_not_pressed_2
   jsr right_is_pressed_2




right_not_pressed_2:


   ;check state of A button of joypad #2
   lda button_state2
   AND #key_a  ; mask out bits
   BEQ a_not_pressed_2
   jsr a_is_pressed_2

a_not_pressed_2:   




   ;Check state of b button on joypad #2
   lda button_state2
   and #key_b
   beq b_not_pressed_2
   jsr b_is_pressed_2



b_not_pressed_2:   


   
   ;Check the state of the left button of joypad #2
   lda button_state2
   and #key_left
   beq left_not_pressed_2
   jsr left_is_pressed_2

left_not_pressed_2:

   ;Check the state of the up arrow of joypad #2
   lda button_state2
   and #key_up
   beq up_not_pressed_2
   jsr up_is_pressed_2

up_not_pressed_2:

   ;Check the state of the up arrow of joypad #3
   lda button_state2
   and #key_down
   beq down_not_pressed_2
   jsr down_is_pressed_2

down_not_pressed_2:



   ;Check if select button is pressed
   lda button_state2
   and #key_select
   beq select_not_pressed_2
   jsr select_is_pressed_2


select_not_pressed_2:



   jmp loop ;Go back and keep reading the joypad forever


updatejoy:

    LDA #1         ; strobe joypad 1
    STA $4016
    LDA #0
    STA $4016

    LDX #$08             ; set X to 8 (the number of times we want to loop, once fo each button)
   


joybuttons:
   
    LDA $4016            ; get button state
    LSR A                ; shift it into the C flag
    ROR button_state     ; rotate C flag into our button_state variable

   
    DEX                  ; decrement X (our loop counter)
    BNE joybuttons       ; jump back to our loop until X is zero
   

   ; Begin reading joypad #2 and store bits in button_state2 variable.


    LDY #$08

joybuttons2:

    LDA $4017            ; get button state
    LSR A                ; shift it into the C flag
    ROR button_state2    ; rotate C flag into our button_state variable

   
    DEY                  ; decrement X (our loop counter)
    BNE joybuttons2      ; jump back to our loop until Y is zero


    rts
      

   
 
right_is_pressed: ; play sound when right arrow is pressed.


        lda #$0F       ; Enable channels
   sta $4015
   
   
   lda #%00111101   ; mode, period
   sta $400E

   lda #%0000000    ; duration
   sta $400F

   

   rts
   

   
left_is_pressed:


   lda #$0F       ; Enable channels
   sta $4015
   
      
   lda #%00010101   ; mode, period
   sta $400E

   lda #%10000000   ; duration
   sta $400F

        rts



up_is_pressed:



   lda #$0F       ; Enable channels
   sta $4015
   
      
   lda #%00111111   ; mode, period  low rumble
   sta $400E

   lda #%0000000    ; duration
   sta $400F


   rts


down_is_pressed:


   lda #$0F       ; Enable channels
   sta $4015
   
         
   lda #%00111110   ; mode, period
   sta $400E

   lda #%11111000   ; duration
   sta $400F

       
   
   rts



a_is_pressed:


   lda #$0F       ; Enable channels
   sta $4015
   
   
   lda #%00010111   ; mode, period
   sta $400E

   lda #%10000000   ; duration
   sta $400F
   
       
      

   rts




b_is_pressed:


   lda #$0F       ; Enable channels
   sta $4015
   
      
   lda #%01011011   ; mode, period  low rumble
   sta $400E

   lda #%00000000    ; duration
   sta $400F

   
        

        rts



select_is_pressed:



   lda #$0F       ; Enable channels
   sta $4015
   

   lda #%10111011   ; mode, period
   sta $400E

   lda #%10101111    ; duration
   sta $400F


   rts


start_is_pressed:


   lda #$0F       ; Enable channels
   sta $4015
   
         
   lda #%11000011   ; mode, period
   sta $400E


   lda #%10101001   ; duration
   sta $400F


   rts


ab_is_pressed:


   rts




   ;JoyPad #2 subroutines below

   


right_is_pressed_2:



   lda #$0F       ; Enable channels
   sta $4015
   
   lda #%00100011   ; enable medium looping with a 1 at bit 5
   sta $400C


   rts







left_is_pressed_2:



   lda #$0F       ; Enable channels
   sta $4015
   
   lda #%00100111   ; enable medium/slow looping with a 1 at bit 5
   sta $400C



   rts


up_is_pressed_2:



   lda #$0F       ; Enable channels
   sta $4015
   
   lda #%00100001   ; enable fast looping with a 1 at bit 5
   sta $400C


   rts



down_is_pressed_2:



   lda #$0F       ; Enable channels
   sta $4015
   
   lda #%00101111   ; enable slow looping
   sta $400C


   rts




a_is_pressed_2:



   rts




b_is_pressed_2:



   rts




start_is_pressed_2:



   rts



select_is_pressed_2:


   jsr start    ; Resets sound to the beginning, clears sound registers:(Stops the volume decay loop).   
   
   rts