Apple-2gs-SW/iigs-game-engine
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Tweak conversion from APU value to DOC register value

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Lucas Scharenbroich 2023-06-12 11:09:21 -05:00
parent 1035af010d
commit 361c7dae56
1 changed files with 50 additions and 13 deletions
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63
demos/smb/apu.s
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@ -299,7 +299,7 @@ default_freq = 5000
pulse1_sound_settings = *
dfb $00+pulse1_oscillator,default_freq ; frequency low register
dfb $20+pulse1_oscillator,default_freq/256 ; frequency high register
dfb $40+pulse1_oscillator,128 ; volume register, volume = 0
dfb $40+pulse1_oscillator,0 ; volume register, volume = 0
dfb $80+pulse1_oscillator,3 ; wavetable pointer register, point to $0300 by default (50% duty cycle)
dfb $c0+pulse1_oscillator,0 ; wavetable size register, 256 byte length
dfb $a0+pulse1_oscillator,0 ; mode register, set to free run
@ -307,7 +307,7 @@ pulse1_sound_settings = *
pulse2_sound_settings = *
dfb $00+pulse2_oscillator,default_freq ; frequency low register
dfb $20+pulse2_oscillator,default_freq/256 ; frequency high register
dfb $40+pulse2_oscillator,120 ; volume register, volume = 0
dfb $40+pulse2_oscillator,0 ; volume register, volume = 0
dfb $80+pulse2_oscillator,3 ; wavetable pointer register, point to $0300 by default (50% duty cycle)
dfb $c0+pulse2_oscillator,0 ; wavetable size register, 256 byte length
dfb $a0+pulse2_oscillator,0 ; mode register, set to free run
@ -315,7 +315,7 @@ pulse2_sound_settings = *
triangle_sound_settings = *
dfb $00+triangle_oscillator,default_freq ; frequency low register
dfb $20+triangle_oscillator,default_freq/256 ; frequency high register
dfb $40+triangle_oscillator,0 ; volume register, volume = 0
dfb $40+triangle_oscillator,128 ; volume register, volume = 0
dfb $80+triangle_oscillator,5 ; wavetable pointer register, point to $0500
dfb $c0+triangle_oscillator,0 ; wavetable size register, 256 byte length
dfb $a0+triangle_oscillator,0 ; mode register, set to free run
@ -404,6 +404,22 @@ interrupt_handler = *
xba
sta sound_data
; Now the triangle wave. This wave needs linear counter support to be silenced
rep #$30
lda APU_TRIANGLE_REG3
jsr get_pulse_freq ; return freq in 16-bic accumulator
lsr
sep #$30
ldx #$00+triangle_oscillator
stx sound_address
sta sound_data
ldx #$20+triangle_oscillator
stx sound_address
xba
sta sound_data
; lda border_color
; inc
; and #$03
@ -438,13 +454,29 @@ set_pulse_volume
sta sound_data
rts
; NES freq = f_CPU / (16 * (t + 1))
; = 1.789773 MHz / (16 * (t + 1))
; = 111860.812 Hz / (t + 1)
;
; IIgs freq = 0.200807 * F_HL (for 32 oscillators with DOC RES = 0)
;
; Solving for F_HL = (1 / 0.200807) * 111860.812 / (t + 1)
; = 557056.338 / (t + 1)
;
; if t < 8 this value is out of range and the scillator should be silenced
;
; otherwise, break apart the ratio
;
; f_HL = 10 * (55706 / (t + 1))
;
get_pulse_freq
mx %00
and #$07FF ; Load the timer value (11-bits); freq = 1.79MHz / (16 * (t - 1)) = 111860Hz / (t-1)
dec
lsr ; Divide top and bottom by 2 -- 55930 / ((t - 1)/2)
cmp #8
bcc :no_sound
inc
sta divisor
lda #55930 ; $DA7A
lda #55706
sta dividend
lda #0
@ -461,12 +493,16 @@ get_pulse_freq
lda dividend
sta dividend
asl
; asl
asl
clc
adc dividend ; multiple by 10 to get the approx DOC value (0.2Hz per + post-multiple)
asl
adc dividend ; multiple by 5 to get the approx DOC value (0.2Hz per)
; sta dividend
rts
:no_sound
lda #0
rts
turn_off_interrupts
php
@ -483,7 +519,8 @@ border_color dw 0
dividend dw 0
divisor dw 0
last_phase1_duty_cycle dfb $ff
last_phase2_duty_cycle dfb $ff
; 8-bit mode
; A = register number
; X = register value
@ -580,19 +617,19 @@ APU_STATUS_WRITE ENT
; Pulse 1 is OSC 0
bit #$01
beq :pulse1_off
_SetDOCReg #$40+pulse1_oscillator;#128
; _SetDOCReg #$40+pulse1_oscillator;#128
bra :pulse1_end
:pulse1_off
_SetDOCReg #$40+pulse1_oscillator;#0
; _SetDOCReg #$40+pulse1_oscillator;#0
:pulse1_end
; Pulse 2 is OSC 2
bit #$02
beq :pulse2_off
_SetDOCReg #$40+pulse2_oscillator;#128
; _SetDOCReg #$40+pulse2_oscillator;#128
bra :pulse2_end
:pulse2_off
_SetDOCReg #$40+pulse2_oscillator;#0
; _SetDOCReg #$40+pulse2_oscillator;#0
:pulse2_end
; Triangle is OSC 4