; sound generation:
; two output channels buffers
; four software channels
; first two hard-panned to left, second two hard-panned to right
; each channel switchable between either pulse, triangle, saw, and noise
; 16-bit oscilators and frequencies for each channel
; 4-bit fine tuners for each channel
; 8-bit volumes for each channel
; 8-bit duty cycle settings for each channel
; enable bits for each channel
;
; music generation:
; tempo
; ticks per frame
; repeat section
; each channel has three notes that are arpeggiated to modulate the target frequency
; each channel has its own target frequency
; each channel has its own frequency sweep speed which is the amount added or substracted from the channel frequency per tick until the target frequency is reached
; each channel has its own target volume
; each channel has its own volume sweep speed which is the amount added or substracted from the channel volume per tick until the target volume is reached
; each channel has its own vibrato settings split between depth and rate which control the effective target frequency
; each channel has its own tremolo settings split between depth and rate which control the effective target volume
; each channel has its own effect that is to be applied per tick
;
; song format:
; 0x00 - tempo
; 0x01 - ticks per frame
; 0x02 - repeat low
; 0x03 - repeat high
; [0x10 - end] - frames
;
; frame format:
; first byte - note
; second byte - volume
; third byte - effect
; fourth byte - arppegio
;
; effect format:
; first nybble - effect
; second nybble - argument
;
; note format:
; first nybble - note
; second nybble - octave
;
; notes:
; 0x0 - null
; 0x1 - same as root (for arppegio notes)
; 0x2 - stop
; 0x3 - revive
; 0x4 - C
; 0x5 - C#
; 0x6 - D
; 0x7 - D#
; 0x8 - E
; 0x9 - F
; 0xA - F#
; 0xB - G
; 0xC - G#
; 0xD - A
; 0xE - A#
; 0xF - B
;
; arppegio format:
; first nybble - note 2 (above octave of note 1)
; second nybble - note 3 (above octave of note 1)
;
; effects:
; 0 - null
; 1 - stop effect
; 2 - set vibrato rate
; 3 - set vibrato depth
; 4 - set tremolo rate
; 5 - set tremolo depth
; 6 - portamento to note
; 7 - volume slide
; 8 - increment duty cycle
; 9 - set duty cycle

.define NOTE_C 262
.define NOTE_Cs 277
.define NOTE_D 294
.define NOTE_Ds 311
.define NOTE_E 330
.define NOTE_F 349
.define NOTE_Fs 370
.define NOTE_G 392
.define NOTE_Gs 415
.define NOTE_A 440
.define NOTE_As 466
.define NOTE_B 494

.def LEFT_BUF = r2
.def RIGHT_BUF = r3

.def CHAN1_OSCL = r4
.def CHAN1_OSCH = r5
.def CHAN2_OSCL = r6
.def CHAN2_OSCH = r7
.def CHAN3_OSCL = r8
.def CHAN3_OSCH = r9
.def CHAN4_OSCL = r10
.def CHAN4_OSCH = r11

.def CHAN1_FRQL = r12
.def CHAN1_FRQH = r13
.def CHAN2_FRQL = r14
.def CHAN2_FRQH = r15
.def CHAN3_FRQL = r24
.def CHAN3_FRQH = r25
.def CHAN4_FRQL = r26
.def CHAN4_FRQH = r27

.def NOISEL = r0
.def NOISEH = r1

.def EFF_DIR = r18

.NOLIST
.include "m48def.inc"
.LIST

.cseg
.org 0x00
	rjmp start

.org 0x09
	rjmp timer

.org 0x40
start:
	ldi r16, LOW(RAMEND)
	out spl, r16
	ldi r16, HIGH(RAMEND)
	out sph, r16

	ldi r16, 1
	sts TIMSK2, r16
	ldi r16, 0b001
	sts TCCR2B, r16

	ldi r16, 0xFF
	out ddrd, r16
	out ddrc, r16

	ldi r16, 0xFF
	mov LEFT_BUF, r16
	mov RIGHT_BUF, r16

	ldi r16, 0x01
	mov NOISEL, r16
	ldi r16, 0x00
	mov NOISEH, r16

	ldi r16, 0b1111
	sts enable, r16

	ldi r16, 0x08
	sts tempo, r16
	ldi r16, 0x06
	sts speed, r16

	ldi r16, 0x2F
	sts chan1_eff, r16
	sts chan2_eff, r16
	sts chan3_eff, r16
	sts chan4_eff, r16

	ldi r16, 0x1F
	sts chan1_vib, r16
	sts chan2_vib, r16
	sts chan3_vib, r16
	sts chan4_vib, r16

	ldi r16, 0x0F
	sts chan1_trm, r16
	sts chan2_trm, r16
	sts chan3_trm, r16
	sts chan4_trm, r16

	ldi r16, 0x40
	sts chan1_tvol, r16
	sts chan2_tvol, r16
	sts chan3_tvol, r16
	sts chan4_tvol, r16

	ldi r16, 0x80
	sts chan1_dut, r16
	sts chan2_dut, r16
	sts chan3_dut, r16
	sts chan4_dut, r16

	ldi r16, 0x64
	sts chan1_notes, r16
	sts chan2_notes, r16
	sts chan3_notes, r16
	sts chan4_notes, r16
	ldi r16, 0x00
	sts chan1_notes + 1, r16
	sts chan2_notes + 1, r16
	sts chan3_notes + 1, r16
	sts chan4_notes + 1, r16

	ldi r16, 0b00000000
	sts waveform, r16

	sei

loop:
	rjmp loop

note_freq:
	mov r16, r19
	lsr r16
	lsr r16
	lsr r16
	lsr r16
	cpi r16, 0x04
	breq setc
	cpi r16, 0x05
	breq setcs
	cpi r16, 0x06
	breq setd
	cpi r16, 0x07
	breq setds
	cpi r16, 0x08
	breq sete
	cpi r16, 0x09
	breq setf
	cpi r16, 0x0A
	breq setfs
	cpi r16, 0x0B
	breq setg
	cpi r16, 0x0C
	breq setgs
	cpi r16, 0x0D
	breq seta
	cpi r16, 0x0E
	breq setas
	cpi r16, 0x0F
	breq setb
	ret
setc:
	ldi r16, LOW(NOTE_C)
	ldi r17, HIGH(NOTE_C)
	rjmp skip4
setcs:
	ldi r16, LOW(NOTE_Cs)
	ldi r17, HIGH(NOTE_Cs)
	rjmp skip4
setd:
	ldi r16, LOW(NOTE_D)
	ldi r17, HIGH(NOTE_D)
	rjmp skip4
setds:
	ldi r16, LOW(NOTE_Ds)
	ldi r17, HIGH(NOTE_Ds)
	rjmp skip4
sete:
	ldi r16, LOW(NOTE_E)
	ldi r17, HIGH(NOTE_E)
	rjmp skip4
setf:
	ldi r16, LOW(NOTE_F)
	ldi r17, HIGH(NOTE_F)
	rjmp skip4
setfs:
	ldi r16, LOW(NOTE_Fs)
	ldi r17, HIGH(NOTE_Fs)
	rjmp skip4
setg:
	ldi r16, LOW(NOTE_G)
	ldi r17, HIGH(NOTE_G)
	rjmp skip4
setgs:
	ldi r16, LOW(NOTE_Gs)
	ldi r17, HIGH(NOTE_Gs)
	rjmp skip4
seta:
	ldi r16, LOW(NOTE_A)
	ldi r17, HIGH(NOTE_A)
	rjmp skip4
setas:
	ldi r16, LOW(NOTE_As)
	ldi r17, HIGH(NOTE_As)
	rjmp skip4
setb:
	ldi r16, LOW(NOTE_B)
	ldi r17, HIGH(NOTE_B)
	rjmp skip4
skip4:
	andi r19, 0x0F
	cpi r19, 0x01
	breq seto1
	cpi r19, 0x02
	breq seto2
	cpi r19, 0x03
	breq seto3
	cpi r19, 0x04
	breq seto4
	cpi r19, 0x05
	breq seto5
	cpi r19, 0x06
	breq seto6
	cpi r19, 0x07
	breq seto7
	cpi r19, 0x08
	breq seto8
	ret
seto1:
	lsr r17
	ror r16
	lsr r17
	ror r16
	lsr r17
	ror r16
	ret
seto2:
	lsr r17
	ror r16
	lsr r17
	ror r16
	ret
seto3:
	lsr r17
	ror r16
	ret
seto4:
	ret
seto5:
	lsl r16
	rol r17
	ret
seto6:
	lsl r16
	rol r17
	lsl r16
	rol r17
	ret
seto7:
	lsl r16
	rol r17
	lsl r16
	rol r17
	lsl r16
	rol r17
	ret
seto8:
	lsl r16
	rol r17
	lsl r16
	rol r17
	lsl r16
	rol r17
	lsl r16
	rol r17
	ret

track:
	ret

arpeggio:
	mov r21, r19
	andi r21, 0xF0
	cpi r16, 1
	breq first
	cpi r16, 2
	breq second
	ret
first:
	andi r20, 0xF0
	andi r19, 0x0F
	cpi r20, 4
	brlo nope2
	cp r21, r20
	brlo nope
	inc r19
nope:
	or r19, r20
	ret
second:
	lsl r20
	lsl r20
	lsl r20
	lsl r20
	andi r19, 0x0F
	cpi r20, 4
	brlo nope2
	cp r21, r20
	brlo nope
	inc r19
nope2:
	or r19, r21
	ret

music:
	clr r18
	sts music_timer, r18
	sts music_timer + 1, r18

	lds r16, tick_timer
	mov r17, r16
	lsr r17
	lsr r17
	lsr r17
	lsr r17
	andi r16, 0x0F
	inc r17
	lds r18, speed
	cp r17, r18
	brlo no_track
	rcall track
	clr r17
	rjmp okay
no_track:
	lsl r17
	lsl r17
	lsl r17
	lsl r17
okay:
	lds r18, fine_tune

	push r17
	push r16

	lds r19, chan1_notes
	lds r20, chan1_notes + 1
	rcall arpeggio
	rcall note_freq

	lds r21, chan1_vib
	mov r22, CHAN1_FRQL
	mov r23, CHAN1_FRQH

	rcall sweep

	mov CHAN1_FRQL, r22
	mov CHAN1_FRQH, r23

	mov r19, r18
	andi r19, 0x0F
	add CHAN1_FRQL, r19

	pop r16
	push r16

	lds r19, chan2_notes
	lds r20, chan2_notes + 1
	rcall arpeggio
	rcall note_freq

	lds r21, chan2_vib
	mov r22, CHAN2_FRQL
	mov r23, CHAN2_FRQH

	rcall sweep

	mov CHAN2_FRQL, r22
	mov CHAN2_FRQH, r23

	lsr r18
	lsr r18
	lsr r18
	lsr r18
	add CHAN2_FRQL, r18

	lds r18, fine_tune + 1

	pop r16
	push r16

	lds r19, chan3_notes
	lds r20, chan3_notes + 1
	rcall arpeggio
	rcall note_freq

	lds r21, chan3_vib
	mov r22, CHAN3_FRQL
	mov r23, CHAN3_FRQH

	rcall sweep

	mov CHAN3_FRQL, r22
	mov CHAN3_FRQH, r23

	mov r19, r18
	andi r19, 0x0F
	add CHAN3_FRQL, r19

	pop r16
	push r16

	lds r19, chan4_notes
	lds r20, chan4_notes + 1
	rcall arpeggio
	rcall note_freq

	lds r21, chan4_vib
	mov r22, CHAN4_FRQL
	mov r23, CHAN4_FRQH

	rcall sweep

	mov CHAN4_FRQL, r22
	mov CHAN4_FRQH, r23

	lsr r18
	lsr r18
	lsr r18
	lsr r18
	add CHAN4_FRQL, r18

	pop r16
	pop r17

	inc r16
	cpi r16, 3
	brlo lower
	clr r16
lower:
	or r17, r16
	sts tick_timer, r17

	lds r16, chan1_trm
	lds r17, chan1_vol
	lds r18, chan1_tvol
	rcall vol_sweep
	sts chan1_vol, r17

	lds r16, chan2_trm
	lds r17, chan2_vol
	lds r18, chan2_tvol
	rcall vol_sweep
	sts chan2_vol, r17

	lds r16, chan3_trm
	lds r17, chan3_vol
	lds r18, chan3_tvol
	rcall vol_sweep
	sts chan3_vol, r17

	lds r16, chan4_trm
	lds r17, chan4_vol
	lds r18, chan4_tvol
	rcall vol_sweep
	sts chan4_vol, r17

	lds r16, chan1_eff
	lds r17, chan1_trm
	lds r18, chan1_vib
	lds r19, chan1_dut
	rcall apply_effect
	sts chan1_trm, r17
	sts chan1_vib, r18
	sts chan1_dut, r19

	lds r16, chan2_eff
	lds r17, chan2_trm
	lds r18, chan2_vib
	lds r19, chan2_dut
	rcall apply_effect
	sts chan2_trm, r17
	sts chan2_vib, r18
	sts chan2_dut, r19

	lds r16, chan3_eff
	lds r17, chan3_trm
	lds r18, chan3_vib
	lds r19, chan3_dut
	rcall apply_effect
	sts chan3_trm, r17
	sts chan3_vib, r18
	sts chan3_dut, r19

	lds r16, chan4_eff
	lds r17, chan4_trm
	lds r18, chan4_vib
	lds r19, chan4_dut
	rcall apply_effect
	sts chan4_trm, r17
	sts chan4_vib, r18
	sts chan4_dut, r19

	ret

apply_effect:
	mov r20, r16
	lsr r16
	lsr r16
	lsr r16
	lsr r16
	andi r20, 0x0F

	cpi r16, 0x2
	breq set_vib_rate
	cpi r16, 0x3
	breq set_vib_depth
	cpi r16, 0x4
	breq set_trm_rate
	cpi r16, 0x5
	breq set_trm_depth
	cpi r16, 0x6
	breq set_portamento
	cpi r16, 0x7
	breq set_vol_slide
	cpi r16, 0x8
	breq inc_dut
	cpi r16, 0x9
	breq set_dut
	ret
set_vib_rate:
	lsl r20
	lsl r20
	lsl r20
	lsl r20
	andi r18, 0x0F
	or r18, r20
	ret
set_vib_depth:
	andi r18, 0xF0
	or r18, r20
	ret
set_trm_rate:
	lsl r20
	lsl r20
	lsl r20
	lsl r20
	andi r17, 0x0F
	or r17, r20
	ret
set_trm_depth:
	andi r17, 0xF0
	or r17, r20
	ret
set_portamento:
	lsl r20
	lsl r20
	lsl r20
	lsl r20
	mov r18, r20
	ret
set_vol_slide:
	lsl r20
	lsl r20
	lsl r20
	lsl r20
	mov r17, r20
	ret
inc_dut:
	add r19, r20
	ret
set_dut:
	lsl r20
	lsl r20
	lsl r20
	lsl r20
	mov r19, r20
	ret

vol_sweep:
	lsr r16
	lsr r16
	lsr r16
	lsr r16
	cpi r16, 0
	breq vol_equal
	cp r17, r18
	brlo vol_smaller
	cp r18, r17
	brlo vol_bigger
	rjmp vol_equal
vol_smaller:
	add r17, r16
	cp r18, r17
	brlo vol_equal
	ret
vol_bigger:
	sub r17, r16
	cp r17, r18
	brlo vol_equal
	ret
vol_equal:
	mov r17, r18
	ret

sweep:
	lsr r21
	lsr r21
	lsr r21
	lsr r21
	cpi r21, 0
	breq equal
	cp r23, r17
	brlo smaller
	cp r17, r23
	brlo bigger
	cp r22, r16
	brlo smaller
	cp r16, r22
	brlo bigger
	rjmp equal
bigger:
	sub r22, r21
	brcc yeah
	dec r23
yeah:
	rjmp done_big
done_big:
	cp r23, r17
	brlo equal
	cp r17, r23
	brlo return2
	cp r22, r16
	brlo equal
	rjmp return2
smaller:
	clr r19
	add r22, r21
	adc r23, r19
	rjmp done_small
done_small:
	cp r23, r17
	brlo return2
	cp r17, r23
	brlo equal
	cp r22, r16
	brlo return2
	cp r16, r22
	brlo equal
	rjmp return2
equal:
	mov r22, r16
	mov r23, r17
return2:
	ret

timer:
	mov r16, LEFT_BUF
	lsr r16
	lsr r16
	mov r17, RIGHT_BUF
	lsr r17
	lsr r17
	out portd, r16
	out portc, r17

	lds r16, music_timer
	lds r17, music_timer + 1
	ldi r18, 0
	ldi r19, 1
	add r16, r19
	adc r17, r18
	sts music_timer, r16
	sts music_timer + 1, r17
	lds r18, tempo
	cp r17, r18
	brlo no_music
	rcall music

no_music:
	clr LEFT_BUF
	clr RIGHT_BUF

	add CHAN1_OSCL, CHAN1_FRQL
	adc CHAN1_OSCH, CHAN1_FRQH
	add CHAN2_OSCL, CHAN2_FRQL
	adc CHAN2_OSCH, CHAN2_FRQH
	add CHAN3_OSCL, CHAN3_FRQL
	adc CHAN3_OSCH, CHAN3_FRQH
	add CHAN4_OSCL, CHAN4_FRQL
	adc CHAN4_OSCH, CHAN4_FRQH

	lds r16, waveform
	lds r22, enable

	mov r18, r16
	andi r18, 0b00000011
	mov r19, CHAN1_OSCH
	lds r20, chan1_vol
	lds r21, chan1_dut
	rcall generate
	sbrc r22, 0
	add LEFT_BUF, r17

	lsr r16
	lsr r16
	mov r18, r16
	andi r18, 0b00000011
	mov r19, CHAN2_OSCH
	lds r20, chan2_vol
	lds r21, chan2_dut
	rcall generate
	sbrc r22, 1
	add LEFT_BUF, r17

	lsr r16
	lsr r16
	mov r18, r16
	andi r18, 0b00000011
	mov r19, CHAN3_OSCH
	lds r20, chan3_vol
	lds r21, chan3_dut
	rcall generate
	sbrc r22, 2
	add RIGHT_BUF, r17

	lsr r16
	lsr r16
	mov r18, r16
	andi r18, 0b00000011
	mov r19, CHAN4_OSCH
	lds r20, chan4_vol
	lds r21, chan4_dut
	rcall generate
	sbrc r22, 3
	add RIGHT_BUF, r17

	reti

generate:
	clr r17
	cpi r18, 0b00
	breq gen_pulse
	cpi r18, 0b01
	breq gen_triangle
	cpi r18, 0b10
	breq gen_saw
	cpi r18, 0b11
	breq gen_noise
	ret

gen_pulse:
	cp r19, r21
	brlo return
	mov r17, r20
	lsr r17
	lsr r17
	ret

gen_triangle:
	mov r17, r19
	sbrc r19, 7
	com r17
	rjmp apply_volume
	ret

gen_saw:
	mov r17, r19
	lsr r17
	lsr r17
	rjmp apply_volume
	ret

gen_noise:
	clr r21
	clr r19
	sbrc NOISEH, 6
	ser r21
	sbrc NOISEL, 3
	ser r19
	eor r19, r21
	clr r21
	lsl NOISEH
	lsl NOISEL
	adc NOISEH, r21
	sbrc r19, 0
	inc NOISEL
	mov r17, NOISEL
	lsr r17
	rjmp apply_volume
	ret

apply_volume:
	sbrc r20, 7
	rjmp return
	lsr r17
	sbrc r20, 6
	rjmp return
	lsr r17
	sbrc r20, 5
	rjmp return
	lsr r17
	sbrc r20, 4
	rjmp return
	lsr r17
	sbrc r20, 3
	rjmp return
	lsr r17
	sbrc r20, 2
	rjmp return
	lsr r17
	sbrc r20, 1
	rjmp return
	lsr r17
return:
	ret

.dseg
chan1_vol: .byte 1
chan2_vol: .byte 1
chan3_vol: .byte 1
chan4_vol: .byte 1

chan1_dut: .byte 1
chan2_dut: .byte 1
chan3_dut: .byte 1
chan4_dut: .byte 1

fine_tune: .byte 2
waveform: .byte 1
enable: .byte 1
music_timer: .byte 2
tick_timer: .byte 1

tempo: .byte 1
speed: .byte 1

chan1_tvol: .byte 1
chan2_tvol: .byte 1
chan3_tvol: .byte 1
chan4_tvol: .byte 1

chan1_notes: .byte 2
chan2_notes: .byte 2
chan3_notes: .byte 2
chan4_notes: .byte 2

chan1_vib: .byte 1
chan2_vib: .byte 1
chan3_vib: .byte 1
chan4_vib: .byte 1

chan1_trm: .byte 1
chan2_trm: .byte 1
chan3_trm: .byte 1
chan4_trm: .byte 1

chan1_eff: .byte 1
chan2_eff: .byte 1
chan3_eff: .byte 1
chan4_eff: .byte 1