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audio.asm
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audio.asm
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; this sub routine inits audio
; side effects:
; overwrites a register
init_audio_channels:
; Init $4000-4013
ldy #$13
@loop: lda @regs,y
sta $4000,y
dey
bpl @loop
; We have to skip over $4014 (OAMDMA)
; enable Square 1, Square 2, Triangle and Noise channels. Disable DMC.
lda #$0F
sta $4015
lda #$40
sta $4017
jsr stop_audio
rts
@regs:
.db $30,$08,$00,$00
.db $30,$08,$00,$00
.db $80,$00,$00,$00
.db $30,$00,$00,$00
.db $00,$00,$00,$00
; stops all sounds on all channels
stop_audio:
; set up audio pointers
lda #<no_audio
sta pulse_ptr_1
sta pulse_ptr_2
sta triangle_ptr
sta noise_ptr
lda #>no_audio
sta pulse_ptr_1+1
sta pulse_ptr_2+1
sta triangle_ptr+1
sta noise_ptr+1
rts
; this sub routine update all audio playback
; inputs:
; pulse, triangle and noise_ptrs
; side effects:
; updates audio timer and registers
; user register a, x, y
update_audio:
; pulse 1 code
ldy #$00
lda (pulse_ptr_1), y
cmp #$FF
beq @not_pulse_1 ; no update
ldx pulse_timer_1
dex
stx pulse_timer_1
bne @not_pulse_1 ; if timer is not 0 do not play yet
ldx pulse_periode_1
stx pulse_timer_1 ; store periode again
; skip update
cmp #$FE
beq @skip_note_pulse1
sta $4000 ; store channel settings
iny
lda (pulse_ptr_1), y
tax ; note offset
lda period_table_hi, x
sta $4003
lda period_table_lo, x
sta $4002
lda pulse_sweep_1
sta $4001
@skip_note_pulse1:
lda pulse_ptr_1
clc
adc #$02 ; add 2 for next pair
sta pulse_ptr_1
lda pulse_ptr_1+1
adc #$00
sta pulse_ptr_1+1
@not_pulse_1:
; pulse 2 code
ldy #$00
lda (pulse_ptr_2), y
cmp #$FF
beq @not_pulse_2 ; no update
ldx pulse_timer_2
dex
stx pulse_timer_2
bne @not_pulse_2 ; if timer is not 0 do not play yet
ldx pulse_periode_2
stx pulse_timer_2 ; store periode again
; skip update
cmp #$FE
beq @skip_note_pulse2:
sta $4004 ; store channel settings
iny
lda (pulse_ptr_2), y
tax ; note offset
lda period_table_hi, x
sta $4007
lda period_table_lo, x
sta $4006
lda pulse_sweep_2
sta $4005
@skip_note_pulse2:
lda pulse_ptr_2
clc
adc #$02 ; add 2 for next pair
sta pulse_ptr_2
lda pulse_ptr_2+1
adc #$00
sta pulse_ptr_2+1
@not_pulse_2:
; triangle code
ldy #$00
lda (triangle_ptr), y
cmp #$FF
beq @not_triangle ; no update
ldx triangle_timer
dex
stx triangle_timer
bne @not_triangle ; if timer is not 0 do not play yet
ldx triangle_periode
stx triangle_timer ; store periode again
cmp #$FE
beq @skip_note_triangle:
sta $4008 ; store channel settings
sta $4017
iny
lda (triangle_ptr), y
tax ; note offset
lda period_table_hi+12, x
sta $400B
lda period_table_lo+12, x
sta $400A
@skip_note_triangle:
lda triangle_ptr
clc
adc #$02 ; add 2 for next pair
sta triangle_ptr
lda triangle_ptr+1
adc #$00
sta triangle_ptr+1
@not_triangle:
; triangle code
ldy #$00
lda (noise_ptr), y
cmp #$FF
beq @not_noise ; no update
ldx noise_timer
dex
stx noise_timer
bne @not_noise ; if timer is not 0 do not play yet
ldx noise_periode
stx noise_timer ; store periode again
cmp #$FE
beq @skip_note_noise ; skip note if FE
sta $400C ; store channel settings
iny
lda (noise_ptr), y
sta $400E
iny
lda (noise_ptr), y
sta $400F
@skip_note_noise:
lda noise_ptr
clc
adc #$03 ; add 3 for next pair
sta noise_ptr
lda noise_ptr+1
adc #$00
sta noise_ptr+1
@not_noise:
rts
; this sub routine plays a cursor beep
; noise
; side effects:
; uses a register
; loads sound into noise channel
init_cursor_beep:
lda #<cursor_noise
sta noise_ptr
lda #>cursor_noise
sta noise_ptr+1
lda #10
sta noise_periode ; 10 frames per periode
lda #$01
sta noise_timer
rts
; this sub routine sets up
; the jump sound
; side effects:
; uses A register
; loads sound into noise channel
init_sword_noise:
init_jump_noise:
lda #<jump_noise
sta noise_ptr
lda #>jump_noise
sta noise_ptr+1
lda #$30
sta noise_periode
lda #$01
sta noise_timer
rts
init_hit_noise:
lda #<hit_noise
sta noise_ptr
lda #>hit_noise
sta noise_ptr+1
lda #$30
sta noise_periode
lda #$01
sta noise_timer
rts
init_push_noise:
lda #<push_noise
sta noise_ptr
lda #>push_noise
sta noise_ptr+1
lda #$20
sta noise_periode
lda #$01
sta noise_timer
rts
init_coin_noise:
lda #<coin_noise
sta noise_ptr
lda #>coin_noise
sta noise_ptr+1
lda #$20
sta noise_periode
lda #$01
sta noise_timer
rts
; this sub routine inits the test song
; side effects:
; uses A register
; loads sound into both square wave channels
; and the triangle channel
init_test_song:
lda #$1F ; periode
sta pulse_periode_1
sta pulse_periode_2
sta triangle_periode
lda #$01
sta pulse_timer_1
sta pulse_timer_2
sta triangle_timer
lda #<test_song_square_1
sta pulse_ptr_1
lda #>test_song_square_1
sta pulse_ptr_1+1
lda #<test_song_square_2
sta pulse_ptr_2
lda #>test_song_square_2
sta pulse_ptr_2+1
lda #<test_song_triangle
sta triangle_ptr
lda #>test_song_triangle
sta triangle_ptr+1
lda #%1000000
sta pulse_sweep_1
sta pulse_sweep_2
rts