impostor music
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@@ -1,13 +1,18 @@
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; -----------------------------------------------------------
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; music.asm - SID music driver skeleton
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; music.asm - SID music driver
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; called once per frame from wait_frame
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; music_init: clear SID registers
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; music_play: placeholder (currently silent)
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; music_init: clear SID, set instruments, restart the song
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; music_play: pattern player tick (once per frame)
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; music_mute / music_unmute: volume control
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;
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; To add music: replace music_play with a real SID player
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; routine (e.g. GoatTracker export), or write patterns into
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; this file using the SID register definitions below.
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; The tune is track 0 ("room work") of the Impostor TIC-80
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; cart, converted from inc/meta/meta.assets.lua:
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; voice 1: bass line (sfx 59, soft sine -> SID triangle)
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; voice 2: drums (sfx 61, TIC-80 noise -> SID noise,
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; C-1 = kick, C-4 = snare)
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; Original timing: tempo 150, speed 5 = 12 rows/s at 60 Hz.
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; On PAL (50 Hz) that is 25 frames per 6 rows, so every
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; sixth row lasts 5 frames instead of 4 (see spd_tbl).
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; -----------------------------------------------------------
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; ---- SID registers ----
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@@ -42,7 +47,15 @@ SID_FC_HI = SID_BASE+22 ; filter cutoff high
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SID_FCTL = SID_BASE+23 ; filter resonance + voice routing
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SID_VOL = SID_BASE+24 ; filter mode (hi nibble) + master volume (lo nibble)
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; ---- initialize SID ----
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; ---- waveform control values ----
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BASS_ON = $11 ; triangle + gate
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BASS_OFF = $10
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DRUM_ON = $81 ; noise + gate
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DRUM_OFF = $80
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SONG_LEN = 128 ; 2 frames x 64 rows
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; ---- initialize SID and restart the song ----
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music_init:
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ldx #24
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lda #0
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@@ -51,20 +64,97 @@ mi_clr:
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dex
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bpl mi_clr
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lda #$00 ; bass: instant attack, full sustain
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sta SID_V1_AD
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lda #$f4
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sta SID_V1_SR
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lda #$05 ; drums: instant attack, ~170 ms decay
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sta SID_V2_AD
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lda #$00
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sta SID_V2_SR
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lda #$0f ; master volume = 15
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sta SID_VOL
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lda #0
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sta mus_muted
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sta mus_row
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sta mus_spd_ix
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lda #1 ; first music_play tick starts row 0
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sta mus_tick
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rts
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; ---- play one tick: called once per frame ----
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; Replace this with a real music player routine.
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music_play:
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lda mus_muted
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bne mp_silent
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; --- insert SID player call here ---
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mp_silent:
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bne mp_done ; muted: song position frozen too
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dec mus_tick
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beq mp_row
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mp_done:
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rts
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mp_row:
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ldx mus_spd_ix ; reload row length (4,4,4,4,4,5 frames)
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lda spd_tbl,x
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sta mus_tick
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inx
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cpx #6
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bne mp_spd_ok
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ldx #0
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mp_spd_ok:
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stx mus_spd_ix
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ldx mus_row
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; ---- voice 1: bass ----
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lda bass_pat,x
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beq mp_drums ; 0 = no event
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cmp #1
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bne mp_bass_note
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lda #BASS_OFF ; 1 = key off
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sta SID_V1_CR
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jmp mp_drums
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mp_bass_note:
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and #$7f ; $80|n = trigger note n
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tay
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lda bass_flo,y
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sta SID_V1_FL
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lda bass_fhi,y
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sta SID_V1_FH
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lda #BASS_OFF ; gate off + on restarts the envelope
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sta SID_V1_CR
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lda #BASS_ON
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sta SID_V1_CR
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; ---- voice 2: drums ----
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mp_drums:
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lda drum_pat,x
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beq mp_next
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cmp #1
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bne mp_drum_note
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lda #DRUM_OFF
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sta SID_V2_CR
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jmp mp_next
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mp_drum_note:
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and #$7f
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tay
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lda drum_flo,y
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sta SID_V2_FL
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lda drum_fhi,y
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sta SID_V2_FH
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lda #DRUM_OFF
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sta SID_V2_CR
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lda #DRUM_ON
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sta SID_V2_CR
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mp_next:
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inx
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cpx #SONG_LEN
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bne mp_store
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ldx #0 ; loop the song
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stx mus_spd_ix ; restart the 4,4,4,4,4,5 cycle with it
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mp_store:
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stx mus_row
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rts
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; ---- mute: silence SID ----
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@@ -81,3 +171,38 @@ music_unmute:
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; ---- state ----
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mus_muted: !byte 0 ; 1 = muted
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mus_row: !byte 0 ; song position (0..SONG_LEN-1)
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mus_tick: !byte 1 ; frames left of the current row
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mus_spd_ix: !byte 0 ; index into spd_tbl
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spd_tbl: !byte 4,4,4,4,4,5 ; 25 frames / 6 rows = 12 rows/s
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; ---- note tables (PAL SID: reg = Hz * 16777216 / 985248) ----
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; bass: 0 = C-2, 1 = A#1, 2 = D#2, 3 = F-2
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bass_flo: !byte $5a,$e0,$2d,$cf
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bass_fhi: !byte $04,$03,$05,$05
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; drums: noise pitch from the TIC-80 note (x32 waveform steps)
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; 0 = C-1 kick (low rumble), 1 = C-4 snare (bright)
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drum_flo: !byte $9c,$ff
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drum_fhi: !byte $45,$ff
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; ---- pattern data: one byte per row per voice ----
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; $00 = nothing, $01 = key off, $80|n = play note n
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bass_pat:
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!byte $80,$00,$00,$00,$01,$00,$80,$00,$01,$00,$00,$00,$81,$00,$80,$00
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!byte $01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$01,$00,$80,$00,$01,$00,$00,$00,$81,$00,$80,$00
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!byte $01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$01,$00,$80,$00,$01,$00,$00,$00,$81,$00,$80,$00
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!byte $01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
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!byte $82,$00,$82,$00,$01,$00,$82,$00,$01,$00,$00,$00,$82,$00,$83,$00
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!byte $01,$00,$83,$00,$01,$00,$83,$00,$83,$00,$01,$00,$83,$00,$01,$00
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drum_pat:
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!byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
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!byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
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