;FamiTone2 v1.12

;settings, uncomment or put them into your main program; the latter makes possible updates easier

; FT_BASE_ADR		= $0300	;page in the RAM used for FT2 variables, should be $xx00
; FT_TEMP			= $00	;3 bytes in zeropage used by the library as a scratchpad
; FT_DPCM_OFF		= $c000	;$c000..$ffc0, 64-byte steps
; FT_SFX_STREAMS	= 4		;number of sound effects played at once, 1..4

; FT_DPCM_ENABLE			;undefine to exclude all DMC code
; FT_SFX_ENABLE			;undefine to exclude all sound effects code
; FT_THREAD				;undefine if you are calling sound effects from the same thread as the sound update call

; FT_PAL_SUPPORT			;undefine to exclude PAL support
; FT_NTSC_SUPPORT			;undefine to exclude NTSC support



;internal defines

	IFCONST FT_PAL_SUPPORT
	IFCONST FT_NTSC_SUPPORT
FT_PITCH_FIX equ 1			;add PAL/NTSC pitch correction code only when both modes are enabled
	ENDIF
	ENDIF

FT_DPCM_PTR		= (FT_DPCM_OFF&$3fff)>>6


;zero page variables

FT_TEMP_PTR			= FT_TEMP		;word
FT_TEMP_PTR_L		= FT_TEMP_PTR+0
FT_TEMP_PTR_H		= FT_TEMP_PTR+1
FT_TEMP_VAR1		= FT_TEMP+2
FT_TEMP_SIZE        = 3

;envelope structure offsets, 5 bytes per envelope, grouped by variable type

FT_ENVELOPES_ALL	= 3+3+3+2	;3 for the pulse and triangle channels, 2 for the noise channel
FT_ENV_STRUCT_SIZE	= 5

FT_ENV_VALUE		= FT_BASE_ADR+0*FT_ENVELOPES_ALL
FT_ENV_REPEAT		= FT_BASE_ADR+1*FT_ENVELOPES_ALL
FT_ENV_ADR_L		= FT_BASE_ADR+2*FT_ENVELOPES_ALL
FT_ENV_ADR_H		= FT_BASE_ADR+3*FT_ENVELOPES_ALL
FT_ENV_PTR			= FT_BASE_ADR+4*FT_ENVELOPES_ALL


;channel structure offsets, 7 bytes per channel

FT_CHANNELS_ALL		= 5
FT_CHN_STRUCT_SIZE	= 9

FT_CHN_PTR_L		= FT_BASE_ADR+0*FT_CHANNELS_ALL
FT_CHN_PTR_H		= FT_BASE_ADR+1*FT_CHANNELS_ALL
FT_CHN_NOTE			= FT_BASE_ADR+2*FT_CHANNELS_ALL
FT_CHN_INSTRUMENT	= FT_BASE_ADR+3*FT_CHANNELS_ALL
FT_CHN_REPEAT		= FT_BASE_ADR+4*FT_CHANNELS_ALL
FT_CHN_RETURN_L		= FT_BASE_ADR+5*FT_CHANNELS_ALL
FT_CHN_RETURN_H		= FT_BASE_ADR+6*FT_CHANNELS_ALL
FT_CHN_REF_LEN		= FT_BASE_ADR+7*FT_CHANNELS_ALL
FT_CHN_DUTY			= FT_BASE_ADR+8*FT_CHANNELS_ALL


;variables and aliases

FT_ENVELOPES	= FT_BASE_ADR
FT_CH1_ENVS		= FT_ENVELOPES+0
FT_CH2_ENVS		= FT_ENVELOPES+3
FT_CH3_ENVS		= FT_ENVELOPES+6
FT_CH4_ENVS		= FT_ENVELOPES+9

FT_CHANNELS		= FT_ENVELOPES+FT_ENVELOPES_ALL*FT_ENV_STRUCT_SIZE
FT_CH1_VARS		= FT_CHANNELS+0
FT_CH2_VARS		= FT_CHANNELS+1
FT_CH3_VARS		= FT_CHANNELS+2
FT_CH4_VARS		= FT_CHANNELS+3
FT_CH5_VARS		= FT_CHANNELS+4


FT_CH1_NOTE			= FT_CH1_VARS+<(FT_CHN_NOTE)
FT_CH2_NOTE			= FT_CH2_VARS+<(FT_CHN_NOTE)
FT_CH3_NOTE			= FT_CH3_VARS+<(FT_CHN_NOTE)
FT_CH4_NOTE			= FT_CH4_VARS+<(FT_CHN_NOTE)
FT_CH5_NOTE			= FT_CH5_VARS+<(FT_CHN_NOTE)

FT_CH1_INSTRUMENT	= FT_CH1_VARS+<(FT_CHN_INSTRUMENT)
FT_CH2_INSTRUMENT	= FT_CH2_VARS+<(FT_CHN_INSTRUMENT)
FT_CH3_INSTRUMENT	= FT_CH3_VARS+<(FT_CHN_INSTRUMENT)
FT_CH4_INSTRUMENT	= FT_CH4_VARS+<(FT_CHN_INSTRUMENT)
FT_CH5_INSTRUMENT	= FT_CH5_VARS+<(FT_CHN_INSTRUMENT)

FT_CH1_DUTY			= FT_CH1_VARS+<(FT_CHN_DUTY)
FT_CH2_DUTY			= FT_CH2_VARS+<(FT_CHN_DUTY)
FT_CH3_DUTY			= FT_CH3_VARS+<(FT_CHN_DUTY)
FT_CH4_DUTY			= FT_CH4_VARS+<(FT_CHN_DUTY)
FT_CH5_DUTY			= FT_CH5_VARS+<(FT_CHN_DUTY)

FT_CH1_VOLUME		= FT_CH1_ENVS+<(FT_ENV_VALUE)+0
FT_CH2_VOLUME		= FT_CH2_ENVS+<(FT_ENV_VALUE)+0
FT_CH3_VOLUME		= FT_CH3_ENVS+<(FT_ENV_VALUE)+0
FT_CH4_VOLUME		= FT_CH4_ENVS+<(FT_ENV_VALUE)+0

FT_CH1_NOTE_OFF		= FT_CH1_ENVS+<(FT_ENV_VALUE)+1
FT_CH2_NOTE_OFF		= FT_CH2_ENVS+<(FT_ENV_VALUE)+1
FT_CH3_NOTE_OFF		= FT_CH3_ENVS+<(FT_ENV_VALUE)+1
FT_CH4_NOTE_OFF		= FT_CH4_ENVS+<(FT_ENV_VALUE)+1

FT_CH1_PITCH_OFF	= FT_CH1_ENVS+<(FT_ENV_VALUE)+2
FT_CH2_PITCH_OFF	= FT_CH2_ENVS+<(FT_ENV_VALUE)+2
FT_CH3_PITCH_OFF	= FT_CH3_ENVS+<(FT_ENV_VALUE)+2


FT_VARS			= FT_CHANNELS+FT_CHANNELS_ALL*FT_CHN_STRUCT_SIZE

FT_PAL_ADJUST	= FT_VARS+0
FT_SONG_LIST_L	= FT_VARS+1
FT_SONG_LIST_H	= FT_VARS+2
FT_INSTRUMENT_L = FT_VARS+3
FT_INSTRUMENT_H = FT_VARS+4
FT_TEMPO_STEP_L	= FT_VARS+5
FT_TEMPO_STEP_H	= FT_VARS+6
FT_TEMPO_ACC_L	= FT_VARS+7
FT_TEMPO_ACC_H	= FT_VARS+8
FT_SONG_SPEED	= FT_CH5_INSTRUMENT
FT_PULSE1_PREV	= FT_CH3_DUTY
FT_PULSE2_PREV	= FT_CH5_DUTY
FT_DPCM_LIST_L	= FT_VARS+9
FT_DPCM_LIST_H	= FT_VARS+10
FT_DPCM_EFFECT  = FT_VARS+11
FT_OUT_BUF		= FT_VARS+12	;11 bytes


;sound effect stream variables, 2 bytes and 15 bytes per stream
;when sound effects are disabled, this memory is not used

FT_SFX_ADR_L		= FT_VARS+23
FT_SFX_ADR_H		= FT_VARS+24
FT_SFX_BASE_ADR		= FT_VARS+25

FT_SFX_STRUCT_SIZE	= 15
FT_SFX_REPEAT		= FT_SFX_BASE_ADR+0
FT_SFX_PTR_L		= FT_SFX_BASE_ADR+1
FT_SFX_PTR_H		= FT_SFX_BASE_ADR+2
FT_SFX_OFF			= FT_SFX_BASE_ADR+3
FT_SFX_BUF			= FT_SFX_BASE_ADR+4	;11 bytes

FT_BASE_SIZE 		= FT_SFX_BUF+11-FT_BASE_ADR

;aliases for sound effect channels to use in user calls

FT_SFX_CH0			= FT_SFX_STRUCT_SIZE*0
FT_SFX_CH1			= FT_SFX_STRUCT_SIZE*1
FT_SFX_CH2			= FT_SFX_STRUCT_SIZE*2
FT_SFX_CH3			= FT_SFX_STRUCT_SIZE*3


;aliases for the APU registers

APU_PL1_VOL		= $4000
APU_PL1_SWEEP	= $4001
APU_PL1_LO		= $4002
APU_PL1_HI		= $4003
APU_PL2_VOL		= $4004
APU_PL2_SWEEP	= $4005
APU_PL2_LO		= $4006
APU_PL2_HI		= $4007
APU_TRI_LINEAR	= $4008
APU_TRI_LO		= $400a
APU_TRI_HI		= $400b
APU_NOISE_VOL	= $400c
APU_NOISE_LO	= $400e
APU_NOISE_HI	= $400f
APU_DMC_FREQ	= $4010
APU_DMC_RAW		= $4011
APU_DMC_START	= $4012
APU_DMC_LEN		= $4013
APU_SND_CHN		= $4015


;aliases for the APU registers in the output buffer

	IFNCONST FT_SFX_ENABLE				;if sound effects are disabled, write to the APU directly
FT_MR_PULSE1_V		= APU_PL1_VOL
FT_MR_PULSE1_L		= APU_PL1_LO
FT_MR_PULSE1_H		= APU_PL1_HI
FT_MR_PULSE2_V		= APU_PL2_VOL
FT_MR_PULSE2_L		= APU_PL2_LO
FT_MR_PULSE2_H		= APU_PL2_HI
FT_MR_TRI_V			= APU_TRI_LINEAR
FT_MR_TRI_L			= APU_TRI_LO
FT_MR_TRI_H			= APU_TRI_HI
FT_MR_NOISE_V		= APU_NOISE_VOL
FT_MR_NOISE_F		= APU_NOISE_LO
	ELSE								;otherwise write to the output buffer
FT_MR_PULSE1_V		= FT_OUT_BUF
FT_MR_PULSE1_L		= FT_OUT_BUF+1
FT_MR_PULSE1_H		= FT_OUT_BUF+2
FT_MR_PULSE2_V		= FT_OUT_BUF+3
FT_MR_PULSE2_L		= FT_OUT_BUF+4
FT_MR_PULSE2_H		= FT_OUT_BUF+5
FT_MR_TRI_V			= FT_OUT_BUF+6
FT_MR_TRI_L			= FT_OUT_BUF+7
FT_MR_TRI_H			= FT_OUT_BUF+8
FT_MR_NOISE_V		= FT_OUT_BUF+9
FT_MR_NOISE_F		= FT_OUT_BUF+10
	ENDIF



;------------------------------------------------------------------------------
; reset APU, initialize FamiTone
; in: A   0 for PAL, not 0 for NTSC
;     X,Y pointer to music data
;------------------------------------------------------------------------------

FamiToneInit: subroutine

	stx FT_SONG_LIST_L		;store music data pointer for further use
	sty FT_SONG_LIST_H
	stx <FT_TEMP_PTR_L
	sty <FT_TEMP_PTR_H

	IFCONST FT_PITCH_FIX
	tax						;set SZ flags for A
	beq .pal
	lda #64
.pal:
	ELSE
	IFCONST FT_PAL_SUPPORT
	lda #0
	ENDIF
	IFCONST FT_NTSC_SUPPORT
	lda #64
	ENDIF
	ENDIF
	sta FT_PAL_ADJUST

	jsr FamiToneMusicStop	;initialize channels and envelopes

	ldy #1
	lda (FT_TEMP_PTR),y		;get instrument list address
	sta FT_INSTRUMENT_L
	iny
	lda (FT_TEMP_PTR),y
	sta FT_INSTRUMENT_H
	iny
	lda (FT_TEMP_PTR),y		;get sample list address
	sta FT_DPCM_LIST_L
	iny
	lda (FT_TEMP_PTR),y
	sta FT_DPCM_LIST_H

	lda #$ff				;previous pulse period MSB, to not write it when not changed
	sta FT_PULSE1_PREV
	sta FT_PULSE2_PREV

	lda #$0f				;enable channels, stop DMC
	sta APU_SND_CHN
	lda #$80				;disable triangle length counter
	sta APU_TRI_LINEAR
	lda #$00				;load noise length
	sta APU_NOISE_HI

	lda #$30				;volumes to 0
	sta APU_PL1_VOL
	sta APU_PL2_VOL
	sta APU_NOISE_VOL
	lda #$08				;no sweep
	sta APU_PL1_SWEEP
	sta APU_PL2_SWEEP

	;jmp FamiToneMusicStop


;------------------------------------------------------------------------------
; stop music that is currently playing, if any
; in: none
;------------------------------------------------------------------------------

FamiToneMusicStop: subroutine

	lda #0
	sta FT_SONG_SPEED		;stop music, reset pause flag
	sta FT_DPCM_EFFECT		;no DPCM effect playing

	ldx #<(FT_CHANNELS)	;initialize channel structures

.set_channels:

	lda #0
	sta FT_CHN_REPEAT,x
	sta FT_CHN_INSTRUMENT,x
	sta FT_CHN_NOTE,x
	sta FT_CHN_REF_LEN,x
	lda #$30
	sta FT_CHN_DUTY,x

	inx						;next channel
	cpx #<(FT_CHANNELS)+FT_CHANNELS_ALL
	bne .set_channels

	ldx #<(FT_ENVELOPES)	;initialize all envelopes to the dummy envelope

.set_envelopes:

	lda #< (_FT2DummyEnvelope)
	sta FT_ENV_ADR_L,x
	lda #>(_FT2DummyEnvelope)
	sta FT_ENV_ADR_H,x
	lda #0
	sta FT_ENV_REPEAT,x
	sta FT_ENV_VALUE,x
	inx
	cpx #<(FT_ENVELOPES)+FT_ENVELOPES_ALL

	bne .set_envelopes

	jmp FamiToneSampleStop


;------------------------------------------------------------------------------
; play music
; in: A number of subsong
;------------------------------------------------------------------------------

FamiToneMusicPlay: subroutine

	ldx FT_SONG_LIST_L
	stx <FT_TEMP_PTR_L
	ldx FT_SONG_LIST_H
	stx <FT_TEMP_PTR_H

	ldy #0
	cmp (FT_TEMP_PTR),y		;check if there is such sub song
	bcs .skip

	asl					;multiply song number by 14
	sta <FT_TEMP_PTR_L		;use pointer LSB as temp variable
	asl
	tax
	asl
	adc <FT_TEMP_PTR_L
	stx <FT_TEMP_PTR_L
	adc <FT_TEMP_PTR_L
	adc #5					;add offset
	tay

	lda FT_SONG_LIST_L		;restore pointer LSB
	sta <FT_TEMP_PTR_L

	jsr FamiToneMusicStop	;stop music, initialize channels and envelopes

	ldx #<(FT_CHANNELS)	;initialize channel structures

.set_channels:

	lda (FT_TEMP_PTR),y		;read channel pointers
	sta FT_CHN_PTR_L,x
	iny
	lda (FT_TEMP_PTR),y
	sta FT_CHN_PTR_H,x
	iny

	lda #0
	sta FT_CHN_REPEAT,x
	sta FT_CHN_INSTRUMENT,x
	sta FT_CHN_NOTE,x
	sta FT_CHN_REF_LEN,x
	lda #$30
	sta FT_CHN_DUTY,x

	inx						;next channel
	cpx #<(FT_CHANNELS)+FT_CHANNELS_ALL
	bne .set_channels


	lda FT_PAL_ADJUST		;read tempo for PAL or NTSC
	beq .pal
	iny
	iny
.pal:

	lda (FT_TEMP_PTR),y		;read the tempo step
	sta FT_TEMPO_STEP_L
	iny
	lda (FT_TEMP_PTR),y
	sta FT_TEMPO_STEP_H


	lda #0					;reset tempo accumulator
	sta FT_TEMPO_ACC_L
	lda #6					;default speed
	sta FT_TEMPO_ACC_H
	sta FT_SONG_SPEED		;apply default speed, this also enables music

.skip:
	rts


;------------------------------------------------------------------------------
; pause and unpause current music
; in: A 0 or not 0 to play or pause
;------------------------------------------------------------------------------

FamiToneMusicPause: subroutine

	tax					;set SZ flags for A
	beq .unpause
	
.pause:

	jsr FamiToneSampleStop
	
	lda #0				;mute sound
	sta FT_CH1_VOLUME
	sta FT_CH2_VOLUME
	sta FT_CH3_VOLUME
	sta FT_CH4_VOLUME
	lda FT_SONG_SPEED	;set pause flag
	ora #$80
	bne .done
.unpause:
	lda FT_SONG_SPEED	;reset pause flag
	and #$7f
.done:
	sta FT_SONG_SPEED

	rts


;------------------------------------------------------------------------------
; update FamiTone state, should be called every NMI
; in: none
;------------------------------------------------------------------------------

FamiToneUpdate: subroutine

	IFCONST FT_THREAD
	lda FT_TEMP_PTR_L
	pha
	lda FT_TEMP_PTR_H
	pha
	ENDIF

	lda FT_SONG_SPEED		;speed 0 means that no music is playing currently
	bmi .pause				;bit 7 set is the pause flag
	bne .update
.pause:
	jmp .update_sound

.update:

	clc						;update frame counter that considers speed, tempo, and PAL/NTSC
	lda FT_TEMPO_ACC_L
	adc FT_TEMPO_STEP_L
	sta FT_TEMPO_ACC_L
	lda FT_TEMPO_ACC_H
	adc FT_TEMPO_STEP_H
	cmp FT_SONG_SPEED
	bcs .update_row			;overflow, row update is needed
	sta FT_TEMPO_ACC_H		;no row update, skip to the envelopes update
	jmp .update_envelopes

.update_row:

	sec
	sbc FT_SONG_SPEED
	sta FT_TEMPO_ACC_H


	ldx #<(FT_CH1_VARS)	;process channel 1
	jsr _FT2ChannelUpdate
	bcc .no_new_note1
	ldx #<(FT_CH1_ENVS)
	lda FT_CH1_INSTRUMENT
	jsr _FT2SetInstrument
	sta FT_CH1_DUTY
.no_new_note1:

	ldx #<(FT_CH2_VARS)	;process channel 2
	jsr _FT2ChannelUpdate
	bcc .no_new_note2
	ldx #<(FT_CH2_ENVS)
	lda FT_CH2_INSTRUMENT
	jsr _FT2SetInstrument
	sta FT_CH2_DUTY
.no_new_note2:

	ldx #<(FT_CH3_VARS)	;process channel 3
	jsr _FT2ChannelUpdate
	bcc .no_new_note3
	ldx #<(FT_CH3_ENVS)
	lda FT_CH3_INSTRUMENT
	jsr _FT2SetInstrument
.no_new_note3:

	ldx #<(FT_CH4_VARS)	;process channel 4
	jsr _FT2ChannelUpdate
	bcc .no_new_note4
	ldx #<(FT_CH4_ENVS)
	lda FT_CH4_INSTRUMENT
	jsr _FT2SetInstrument
	sta FT_CH4_DUTY
.no_new_note4:

	IFCONST FT_DPCM_ENABLE

	ldx #<(FT_CH5_VARS)	;process channel 5
	jsr _FT2ChannelUpdate
	bcc .no_new_note5
	lda FT_CH5_NOTE
	bne .play_sample
	jsr FamiToneSampleStop
	bne .no_new_note5		;A is non-zero after FamiToneSampleStop
.play_sample:
	jsr FamiToneSamplePlayM
.no_new_note5:

	ENDIF


.update_envelopes:

	ldx #<(FT_ENVELOPES)	;process 11 envelopes

.env_process:

	lda FT_ENV_REPEAT,x		;check envelope repeat counter
	beq .env_read			;if it is zero, process envelope
	dec FT_ENV_REPEAT,x		;otherwise decrement the counter
	bne .env_next

.env_read:

	lda FT_ENV_ADR_L,x		;load envelope data address into temp
	sta <FT_TEMP_PTR_L
	lda FT_ENV_ADR_H,x
	sta <FT_TEMP_PTR_H
	ldy FT_ENV_PTR,x		;load envelope pointer

.env_read_value:

	lda (FT_TEMP_PTR),y		;read a byte of the envelope data
	bpl .env_special		;values below 128 used as a special code, loop or repeat
	clc						;values above 128 are output value+192 (output values are signed -63..64)
	adc #256-192
	sta FT_ENV_VALUE,x		;store the output value
	iny						;advance the pointer
	bne .env_next_store_ptr ;bra

.env_special:

	bne .env_set_repeat		;zero is the loop point, non-zero values used for the repeat counter
	iny						;advance the pointer
	lda (FT_TEMP_PTR),y		;read loop position
	tay						;use loop position
	jmp .env_read_value		;read next byte of the envelope

.env_set_repeat:

	iny
	sta FT_ENV_REPEAT,x		;store the repeat counter value

.env_next_store_ptr:

	tya						;store the envelope pointer
	sta FT_ENV_PTR,x

.env_next:

	inx						;next envelope

	cpx #<(FT_ENVELOPES)+FT_ENVELOPES_ALL
	bne .env_process


.update_sound:

	;convert envelope and channel output data into APU register values in the output buffer

	lda FT_CH1_NOTE
	beq .ch1cut
	clc
	adc FT_CH1_NOTE_OFF
	IFCONST FT_PITCH_FIX
	ora FT_PAL_ADJUST
	ENDIF
	tax
	lda FT_CH1_PITCH_OFF
	tay
	adc _FT2NoteTableLSB,x
	sta FT_MR_PULSE1_L
	tya						;sign extension for the pitch offset
	ora #$7f
	bmi .ch1sign
	lda #0
.ch1sign:
	adc _FT2NoteTableMSB,x

	IFNCONST FT_SFX_ENABLE
	cmp FT_PULSE1_PREV
	beq .ch1prev
	sta FT_PULSE1_PREV
	ENDIF

	sta FT_MR_PULSE1_H
.ch1prev:
	lda FT_CH1_VOLUME
.ch1cut:
	ora FT_CH1_DUTY
	sta FT_MR_PULSE1_V


	lda FT_CH2_NOTE
	beq .ch2cut
	clc
	adc FT_CH2_NOTE_OFF
	IFCONST FT_PITCH_FIX
	ora FT_PAL_ADJUST
	ENDIF
	tax
	lda FT_CH2_PITCH_OFF
	tay
	adc _FT2NoteTableLSB,x
	sta FT_MR_PULSE2_L
	tya
	ora #$7f
	bmi .ch2sign
	lda #0
.ch2sign:
	adc _FT2NoteTableMSB,x

	IFNCONST FT_SFX_ENABLE
	cmp FT_PULSE2_PREV
	beq .ch2prev
	sta FT_PULSE2_PREV
	ENDIF

	sta FT_MR_PULSE2_H
.ch2prev:
	lda FT_CH2_VOLUME
.ch2cut:
	ora FT_CH2_DUTY
	sta FT_MR_PULSE2_V


	lda FT_CH3_NOTE
	beq .ch3cut
	clc
	adc FT_CH3_NOTE_OFF
	IFCONST FT_PITCH_FIX
	ora FT_PAL_ADJUST
	ENDIF
	tax
	lda FT_CH3_PITCH_OFF
	tay
	adc _FT2NoteTableLSB,x
	sta FT_MR_TRI_L
	tya
	ora #$7f
	bmi .ch3sign
	lda #0
.ch3sign:
	adc _FT2NoteTableMSB,x
	sta FT_MR_TRI_H
	lda FT_CH3_VOLUME
.ch3cut:
	ora #$80
	sta FT_MR_TRI_V


	lda FT_CH4_NOTE
	beq .ch4cut
	clc
	adc FT_CH4_NOTE_OFF
	and #$0f
	eor #$0f
	sta <FT_TEMP_VAR1
	lda FT_CH4_DUTY
	asl
	and #$80
	ora <FT_TEMP_VAR1
	sta FT_MR_NOISE_F
	lda FT_CH4_VOLUME
.ch4cut:
	ora #$f0
	sta FT_MR_NOISE_V


	IFCONST FT_SFX_ENABLE

	;process all sound effect streams

	.if FT_SFX_STREAMS>0
	ldx #FT_SFX_CH0
	jsr _FT2SfxUpdate
	ENDIF
	.if FT_SFX_STREAMS>1
	ldx #FT_SFX_CH1
	jsr _FT2SfxUpdate
	ENDIF
	.if FT_SFX_STREAMS>2
	ldx #FT_SFX_CH2
	jsr _FT2SfxUpdate
	ENDIF
	.if FT_SFX_STREAMS>3
	ldx #FT_SFX_CH3
	jsr _FT2SfxUpdate
	ENDIF


	;send data from the output buffer to the APU

	lda FT_OUT_BUF		;pulse 1 volume
	sta APU_PL1_VOL
	lda FT_OUT_BUF+1	;pulse 1 period LSB
	sta APU_PL1_LO
	lda FT_OUT_BUF+2	;pulse 1 period MSB, only applied when changed
	cmp FT_PULSE1_PREV
	beq .no_pulse1_upd
	sta FT_PULSE1_PREV
	sta APU_PL1_HI
.no_pulse1_upd:

	lda FT_OUT_BUF+3	;pulse 2 volume
	sta APU_PL2_VOL
	lda FT_OUT_BUF+4	;pulse 2 period LSB
	sta APU_PL2_LO
	lda FT_OUT_BUF+5	;pulse 2 period MSB, only applied when changed
	cmp FT_PULSE2_PREV
	beq .no_pulse2_upd
	sta FT_PULSE2_PREV
	sta APU_PL2_HI
.no_pulse2_upd:

	lda FT_OUT_BUF+6	;triangle volume (plays or not)
	sta APU_TRI_LINEAR
	lda FT_OUT_BUF+7	;triangle period LSB
	sta APU_TRI_LO
	lda FT_OUT_BUF+8	;triangle period MSB
	sta APU_TRI_HI

	lda FT_OUT_BUF+9	;noise volume
	sta APU_NOISE_VOL
	lda FT_OUT_BUF+10	;noise period
	sta APU_NOISE_LO

	ENDIF

	IFCONST FT_THREAD
	pla
	sta FT_TEMP_PTR_H
	pla
	sta FT_TEMP_PTR_L
	ENDIF

	rts


;internal routine, sets up envelopes of a channel according to current instrument
;in X envelope group offset, A instrument number

_FT2SetInstrument: subroutine
	asl					;instrument number is pre multiplied by 4
	tay
	lda FT_INSTRUMENT_H
	adc #0					;use carry to extend range for 64 instruments
	sta <FT_TEMP_PTR_H
	lda FT_INSTRUMENT_L
	sta <FT_TEMP_PTR_L

	lda (FT_TEMP_PTR),y		;duty cycle
	sta <FT_TEMP_VAR1
	iny

	lda (FT_TEMP_PTR),y		;instrument pointer LSB
	sta FT_ENV_ADR_L,x
	iny
	lda (FT_TEMP_PTR),y		;instrument pointer MSB
	iny
	sta FT_ENV_ADR_H,x
	inx						;next envelope

	lda (FT_TEMP_PTR),y		;instrument pointer LSB
	sta FT_ENV_ADR_L,x
	iny
	lda (FT_TEMP_PTR),y		;instrument pointer MSB
	sta FT_ENV_ADR_H,x

	lda #0
	sta FT_ENV_REPEAT-1,x	;reset env1 repeat counter
	sta FT_ENV_PTR-1,x		;reset env1 pointer
	sta FT_ENV_REPEAT,x		;reset env2 repeat counter
	sta FT_ENV_PTR,x		;reset env2 pointer

	cpx #<(FT_CH4_ENVS)	;noise channel has only two envelopes
	bcs .no_pitch

	inx						;next envelope
	iny
	sta FT_ENV_REPEAT,x		;reset env3 repeat counter
	sta FT_ENV_PTR,x		;reset env3 pointer
	lda (FT_TEMP_PTR),y		;instrument pointer LSB
	sta FT_ENV_ADR_L,x
	iny
	lda (FT_TEMP_PTR),y		;instrument pointer MSB
	sta FT_ENV_ADR_H,x

.no_pitch:
	lda <FT_TEMP_VAR1
	rts


;internal routine, parses channel note data

_FT2ChannelUpdate: subroutine

	lda FT_CHN_REPEAT,x		;check repeat counter
	beq .no_repeat
	dec FT_CHN_REPEAT,x		;decrease repeat counter
	clc						;no new note
	rts

.no_repeat:
	lda FT_CHN_PTR_L,x		;load channel pointer into temp
	sta <FT_TEMP_PTR_L
	lda FT_CHN_PTR_H,x
	sta <FT_TEMP_PTR_H
.no_repeat_r:
	ldy #0

.read_byte:
	lda (FT_TEMP_PTR),y		;read byte of the channel

	inc <FT_TEMP_PTR_L		;advance pointer
	bne .no_inc_ptr1
	inc <FT_TEMP_PTR_H
.no_inc_ptr1:

	ora #0
	bmi .special_code		;bit 7 0=note 1=special code

	lsr					;bit 0 set means the note is followed by an empty row
	bcc .no_empty_row
	inc FT_CHN_REPEAT,x		;set repeat counter to 1
.no_empty_row:
	sta FT_CHN_NOTE,x		;store note code
	sec						;new note flag is set
	bcs .done ;bra

.special_code:
	and #$7f
	lsr
	bcs .set_empty_rows
	asl
	asl
	sta FT_CHN_INSTRUMENT,x	;store instrument number*4
	bcc .read_byte ;bra

.set_empty_rows:
	cmp #$3d
	bcc .set_repeat
	beq .set_speed
	cmp #$3e
	beq .set_loop

.set_reference:
	clc						;remember return address+3
	lda <FT_TEMP_PTR_L
	adc #3
	sta FT_CHN_RETURN_L,x
	lda <FT_TEMP_PTR_H
	adc #0
	sta FT_CHN_RETURN_H,x
	lda (FT_TEMP_PTR),y		;read length of the reference (how many rows)
	sta FT_CHN_REF_LEN,x
	iny
	lda (FT_TEMP_PTR),y		;read 16-bit absolute address of the reference
	sta <FT_TEMP_VAR1		;remember in temp
	iny
	lda (FT_TEMP_PTR),y
	sta <FT_TEMP_PTR_H
	lda <FT_TEMP_VAR1
	sta <FT_TEMP_PTR_L
	ldy #0
	jmp .read_byte

.set_speed:
	lda (FT_TEMP_PTR),y
	sta FT_SONG_SPEED
	inc <FT_TEMP_PTR_L		;advance pointer after reading the speed value
	bne .read_byte
	inc <FT_TEMP_PTR_H
	bne .read_byte ;bra

.set_loop:
	lda (FT_TEMP_PTR),y
	sta <FT_TEMP_VAR1
	iny
	lda (FT_TEMP_PTR),y
	sta <FT_TEMP_PTR_H
	lda <FT_TEMP_VAR1
	sta <FT_TEMP_PTR_L
	dey
	jmp .read_byte

.set_repeat:
	sta FT_CHN_REPEAT,x		;set up repeat counter, carry is clear, no new note

.done:
	lda FT_CHN_REF_LEN,x	;check reference row counter
	beq .no_ref				;if it is zero, there is no reference
	dec FT_CHN_REF_LEN,x	;decrease row counter
	bne .no_ref

	lda FT_CHN_RETURN_L,x	;end of a reference, return to previous pointer
	sta FT_CHN_PTR_L,x
	lda FT_CHN_RETURN_H,x
	sta FT_CHN_PTR_H,x
	rts

.no_ref:
	lda <FT_TEMP_PTR_L
	sta FT_CHN_PTR_L,x
	lda <FT_TEMP_PTR_H
	sta FT_CHN_PTR_H,x
	rts



;------------------------------------------------------------------------------
; stop DPCM sample if it plays
;------------------------------------------------------------------------------

FamiToneSampleStop: subroutine

	lda #%00001111
	sta APU_SND_CHN

	rts


	
	IFCONST FT_DPCM_ENABLE

;------------------------------------------------------------------------------
; play DPCM sample, used by music player, could be used externally
; in: A is number of a sample, 1..63
;------------------------------------------------------------------------------

FamiToneSamplePlayM: subroutine		;for music (low priority)

	ldx FT_DPCM_EFFECT
	beq _FT2SamplePlay
	tax
	lda APU_SND_CHN
	and #16
	beq .not_busy
	rts

.not_busy:
	sta FT_DPCM_EFFECT
	txa
	jmp _FT2SamplePlay

;------------------------------------------------------------------------------
; play DPCM sample with higher priority, for sound effects
; in: A is number of a sample, 1..63
;------------------------------------------------------------------------------

FamiToneSamplePlay: subroutine

	ldx #1
	stx FT_DPCM_EFFECT

_FT2SamplePlay:

	sta <FT_TEMP		;sample number*3, offset in the sample table
	asl
	clc
	adc <FT_TEMP
	
	adc FT_DPCM_LIST_L
	sta <FT_TEMP_PTR_L
	lda #0
	adc FT_DPCM_LIST_H
	sta <FT_TEMP_PTR_H

	lda #%00001111			;stop DPCM
	sta APU_SND_CHN

	ldy #0
	lda (FT_TEMP_PTR),y		;sample offset
	sta APU_DMC_START
	iny
	lda (FT_TEMP_PTR),y		;sample length
	sta APU_DMC_LEN
	iny
	lda (FT_TEMP_PTR),y		;pitch and loop
	sta APU_DMC_FREQ

	lda #32					;reset DAC counter
	sta APU_DMC_RAW
	lda #%00011111			;start DMC
	sta APU_SND_CHN

	rts

	ENDIF

	IFCONST FT_SFX_ENABLE

;------------------------------------------------------------------------------
; init sound effects player, set pointer to data
; in: X,Y is address of sound effects data
;------------------------------------------------------------------------------

FamiToneSfxInit: subroutine

	stx <FT_TEMP_PTR_L
	sty <FT_TEMP_PTR_H
	
	ldy #0
	
	IFCONST FT_PITCH_FIX

	lda FT_PAL_ADJUST		;add 2 to the sound list pointer for PAL
	bne .ntsc
	iny
	iny
.ntsc:

	ENDIF
	
	lda (FT_TEMP_PTR),y		;read and store pointer to the effects list
	sta FT_SFX_ADR_L
	iny
	lda (FT_TEMP_PTR),y
	sta FT_SFX_ADR_H

	ldx #FT_SFX_CH0			;init all the streams

.set_channels:
	jsr _FT2SfxClearChannel
	txa
	clc
	adc #FT_SFX_STRUCT_SIZE
	tax
	cpx #FT_SFX_STRUCT_SIZE*FT_SFX_STREAMS
	bne .set_channels

	rts


;internal routine, clears output buffer of a sound effect
;in: A is 0
;    X is offset of sound effect stream

_FT2SfxClearChannel: subroutine

	lda #0
	sta FT_SFX_PTR_H,x		;this stops the effect
	sta FT_SFX_REPEAT,x
	sta FT_SFX_OFF,x
	sta FT_SFX_BUF+6,x		;mute triangle
	lda #$30
	sta FT_SFX_BUF+0,x		;mute pulse1
	sta FT_SFX_BUF+3,x		;mute pulse2
	sta FT_SFX_BUF+9,x		;mute noise

	rts


;------------------------------------------------------------------------------
; play sound effect
; in: A is a number of the sound effect 0..127
;     X is offset of sound effect channel, should be FT_SFX_CH0..FT_SFX_CH3
;------------------------------------------------------------------------------

FamiToneSfxPlay: subroutine

	asl					;get offset in the effects list
	tay

	jsr _FT2SfxClearChannel	;stops the effect if it plays

	lda FT_SFX_ADR_L
	sta <FT_TEMP_PTR_L
	lda FT_SFX_ADR_H
	sta <FT_TEMP_PTR_H

	lda (FT_TEMP_PTR),y		;read effect pointer from the table
	sta FT_SFX_PTR_L,x		;store it
	iny
	lda (FT_TEMP_PTR),y
	sta FT_SFX_PTR_H,x		;this write enables the effect

	rts


;internal routine, update one sound effect stream
;in: X is offset of sound effect stream

_FT2SfxUpdate: subroutine

	lda FT_SFX_REPEAT,x		;check if repeat counter is not zero
	beq .no_repeat
	dec FT_SFX_REPEAT,x		;decrement and return
	bne .update_buf			;just mix with output buffer

.no_repeat:
	lda FT_SFX_PTR_H,x		;check if MSB of the pointer is not zero
	bne .sfx_active
	rts						;return otherwise, no active effect

.sfx_active:
	sta <FT_TEMP_PTR_H		;load effect pointer into temp
	lda FT_SFX_PTR_L,x
	sta <FT_TEMP_PTR_L
	ldy FT_SFX_OFF,x
	clc

.read_byte:
	lda (FT_TEMP_PTR),y		;read byte of effect
	bmi .get_data			;if bit 7 is set, it is a register write
	beq .eof
	iny
	sta FT_SFX_REPEAT,x		;if bit 7 is reset, it is number of repeats
	tya
	sta FT_SFX_OFF,x
	jmp .update_buf

.get_data:
	iny
	stx <FT_TEMP_VAR1		;it is a register write
	adc <FT_TEMP_VAR1		;get offset in the effect output buffer
	tax
	lda (FT_TEMP_PTR),y		;read value
	iny
	sta FT_SFX_BUF-128,x	;store into output buffer
	ldx <FT_TEMP_VAR1
	jmp .read_byte			;and read next byte

.eof:
	sta FT_SFX_PTR_H,x		;mark channel as inactive

.update_buf:

	lda FT_OUT_BUF			;compare effect output buffer with main output buffer
	and #$0f				;if volume of pulse 1 of effect is higher than that of the
	sta <FT_TEMP_VAR1		;main buffer, overwrite the main buffer value with the new one
	lda FT_SFX_BUF+0,x
	and #$0f
	cmp <FT_TEMP_VAR1
	bcc .no_pulse1
	lda FT_SFX_BUF+0,x
	sta FT_OUT_BUF+0
	lda FT_SFX_BUF+1,x
	sta FT_OUT_BUF+1
	lda FT_SFX_BUF+2,x
	sta FT_OUT_BUF+2
.no_pulse1:

	lda FT_OUT_BUF+3		;same for pulse 2
	and #$0f
	sta <FT_TEMP_VAR1
	lda FT_SFX_BUF+3,x
	and #$0f
	cmp <FT_TEMP_VAR1
	bcc .no_pulse2
	lda FT_SFX_BUF+3,x
	sta FT_OUT_BUF+3
	lda FT_SFX_BUF+4,x
	sta FT_OUT_BUF+4
	lda FT_SFX_BUF+5,x
	sta FT_OUT_BUF+5
.no_pulse2:

	lda FT_SFX_BUF+6,x		;overwrite triangle of main output buffer if it is active
	beq .no_triangle
	sta FT_OUT_BUF+6
	lda FT_SFX_BUF+7,x
	sta FT_OUT_BUF+7
	lda FT_SFX_BUF+8,x
	sta FT_OUT_BUF+8
.no_triangle:

	lda FT_OUT_BUF+9		;same as for pulse 1 and 2, but for noise
	and #$0f
	sta <FT_TEMP_VAR1
	lda FT_SFX_BUF+9,x
	and #$0f
	cmp <FT_TEMP_VAR1
	bcc .no_noise
	lda FT_SFX_BUF+9,x
	sta FT_OUT_BUF+9
	lda FT_SFX_BUF+10,x
	sta FT_OUT_BUF+10
.no_noise:

	rts

	ENDIF


;dummy envelope used to initialize all channels with silence

_FT2DummyEnvelope:
	.byte $c0,$00,$00

;PAL and NTSC, 11-bit dividers
;rest note, then octaves 1-5, then three zeroes
;first 64 bytes are PAL, next 64 bytes are NTSC

_FT2NoteTableLSB:
	IFCONST FT_PAL_SUPPORT
	.byte $00,$33,$da,$86,$36,$eb,$a5,$62,$23,$e7,$af,$7a,$48,$19,$ec,$c2
	.byte $9a,$75,$52,$30,$11,$f3,$d7,$bc,$a3,$8c,$75,$60,$4c,$3a,$28,$17
	.byte $08,$f9,$eb,$dd,$d1,$c5,$ba,$af,$a5,$9c,$93,$8b,$83,$7c,$75,$6e
	.byte $68,$62,$5c,$57,$52,$4d,$49,$45,$41,$3d,$3a,$36,$33,$30,$2d,$2b
	ENDIF
	IFCONST FT_NTSC_SUPPORT
	.byte $00,$ad,$4d,$f2,$9d,$4c,$00,$b8,$74,$34,$f7,$be,$88,$56,$26,$f8
	.byte $ce,$a5,$7f,$5b,$39,$19,$fb,$de,$c3,$aa,$92,$7b,$66,$52,$3f,$2d
	.byte $1c,$0c,$fd,$ee,$e1,$d4,$c8,$bd,$b2,$a8,$9f,$96,$8d,$85,$7e,$76
	.byte $70,$69,$63,$5e,$58,$53,$4f,$4a,$46,$42,$3e,$3a,$37,$34,$31,$2e
	ENDIF
_FT2NoteTableMSB:
	IFCONST FT_PAL_SUPPORT
	.byte $00,$06,$05,$05,$05,$04,$04,$04,$04,$03,$03,$03,$03,$03,$02,$02
	.byte $02,$02,$02,$02,$02,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01
	.byte $01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
	.byte $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
	ENDIF
	IFCONST FT_NTSC_SUPPORT
	.byte $00,$06,$06,$05,$05,$05,$05,$04,$04,$04,$03,$03,$03,$03,$03,$02
	.byte $02,$02,$02,$02,$02,$02,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01
	.byte $01,$01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
	.byte $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
	ENDIF