Written by Emberlynn Bland.
It is highly recomended you read the music documentation before continuing.
GBT Player can be compiled to use a different set of 8 pre-determined waveforms for Channel 3, compared to the defaults that are mentioned in the music docs. This lets you edit all 8 waveforms for Channel 3 on a per-game basis. These 8 waveforms can not be swapped-out during gameplay.
After using Engine Eject (2.0.0 and above) the file gbt_player_bank1.s can be found inside of assets/engine/src/core. Lines 40 to 47 contain sets of nibbles that determine the waveform shape for each of Channel 3's instruments.
Each line contains 32 nibbles joined together in groups of 2. Each nibble represents the amplitude of a sample from 0 to F.
Example:
gbt_wave: ; unofficial edit
.DB 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ; square wave
.DB 0x79,0xBC,0xDE,0xEF,0xFF,0xEE,0xDC,0xB9,0x75,0x43,0x21,0x10,0x00,0x11,0x23,0x45 ; sine wave
.DB 0xFF,0xEE,0xDD,0xCC,0xBB,0xAA,0x99,0x88,0x77,0x66,0x55,0x44,0x33,0x22,0x11,0x00 ; sawtooth
.DB 0x00,0x11,0x22,0x33,0x44,0x55,0x66,0x77,0x88,0x77,0x66,0x55,0x44,0x33,0x22,0x11 ; triangle
.DB 0xFE,0xDC,0xBA,0x98,0x76,0x54,0x32,0x10,0x12,0x34,0x45,0x56,0x78,0x9A,0xBC,0xDE ; double-speed triangle
Example: 0xFF represents two samples of maximum amplitude. One set to F amplitude, the other set to F amplitude.
Example: 0x00 represents two samples of minimum amplitude. One set to 0 amplitude, the other set to 0 amplitude.
Example: 0x0F represents two samples of mixed amplitude. One set to 0 amplitude, the other set to F amplitude.
So long as the formatting of the nibbles remain the same, their values can be changed to any 16-bit value to create waveforms other than the GBT Player defaults. Changing the in-game samples here will not update the samples in template.mod, so adjust these samples with this in mind. hUGETracker features a sample-drawing tool that shows the necessary nibbles to create your desired waveform.
Here's a new waveform that can not be found in GBT Player by default:
gbt_wave: ; unofficial edit
.DB 0x00,0x11,0x22,0x33,0x44,0x55,0x66,0x77,0x88,0x77,0x66,0x55,0x44,0x33,0x22,0x11 ; triangle wave
Replacing one of the instruments with the above code will change the corrosponding instrument to your new waveform.
To cap this off, here's an example of me switching the default Sine wave with a Triangle wave:
;-------------------------------------------------------------------------------
;
; GBT Player v2.2.0
;
; SPDX-License-Identifier: MIT
;
; Copyright (c) 2009-2020, Antonio Niño Díaz <antonio_nd@outlook.com>
;
;-------------------------------------------------------------------------------
.NR10 = 0xFF10
.NR11 = 0xFF11
.NR12 = 0xFF12
.NR13 = 0xFF13
.NR14 = 0xFF14
.NR21 = 0xFF16
.NR22 = 0xFF17
.NR23 = 0xFF18
.NR24 = 0xFF19
.NR30 = 0xFF1A
.NR31 = 0xFF1B
.NR32 = 0xFF1C
.NR33 = 0xFF1D
.NR34 = 0xFF1E
.NR41 = 0xFF20
.NR42 = 0xFF21
.NR43 = 0xFF22
.NR44 = 0xFF23
.NR50 = 0xFF24
.NR51 = 0xFF25
.NR52 = 0xFF26
;-------------------------------------------------------------------------------
.area _CODE_1
;-------------------------------------------------------------------------------
gbt_wave: ; 8 sounds
.DB 0xA5,0xD7,0xC9,0xE1,0xBC,0x9A,0x76,0x31,0x0C,0xBA,0xDE,0x60,0x1B,0xCA,0x03,0x93 ; random :P
.DB 0x00,0x11,0x22,0x33,0x44,0x55,0x66,0x77,0x88,0x77,0x66,0x55,0x44,0x33,0x22,0x11 ; ember triangle
.DB 0xFD,0xEC,0xDB,0xCA,0xB9,0xA8,0x97,0x86,0x79,0x68,0x57,0x46,0x35,0x24,0x13,0x02 ; little up-downs
.DB 0xDE,0xFE,0xDC,0xBA,0x9A,0xA9,0x87,0x77,0x88,0x87,0x65,0x56,0x54,0x32,0x10,0x12
.DB 0xAB,0xCD,0xEF,0xED,0xCB,0xA0,0x12,0x3E,0xDC,0xBA,0xBC,0xDE,0xFE,0xDC,0x32,0x10 ; triangular broken
.DB 0xFF,0xEE,0xDD,0xCC,0xBB,0xAA,0x99,0x88,0x77,0x66,0x55,0x44,0x33,0x22,0x11,0x00 ; triangular
.DB 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ; square 50%
.DB 0x79,0xBC,0xDE,0xEF,0xFF,0xEE,0xDC,0xB9,0x75,0x43,0x21,0x10,0x00,0x11,0x23,0x45 ; sine
; gbt_noise: ; Moved to Mod2GBT for better note range & performance
; 7 bit, can adjust with pitch C D# F# A# C
;.DB 0x5F,0x4E,0x3E,0x2F,0x2E,0x2C,0x1F,0x0F
; 15 bit
;.DB 0x64,0x54,0x44,0x24,0x00
;.DB 0x67,0x56,0x46
gbt_frequencies:
.DW 44, 156, 262, 363, 457, 547, 631, 710, 786, 854, 923, 986
.DW 1046, 1102, 1155, 1205, 1253, 1297, 1339, 1379, 1417, 1452, 1486, 1517
.DW 1546, 1575, 1602, 1627, 1650, 1673, 1694, 1714, 1732, 1750, 1767, 1783
.DW 1798, 1812, 1825, 1837, 1849, 1860, 1871, 1881, 1890, 1899, 1907, 1915
.DW 1923, 1930, 1936, 1943, 1949, 1954, 1959, 1964, 1969, 1974, 1978, 1982
.DW 1985, 1988, 1992, 1995, 1998, 2001, 2004, 2006, 2009, 2011, 2013, 2015
;-------------------------------------------------------------------------------
_gbt_get_freq_from_index: ; a = index, bc = returned freq
ld hl,#gbt_frequencies
ld c,a
ld b,#0
add hl,bc
add hl,bc
ld c,(hl)
inc hl
ld b,(hl)
ret
;-------------------------------------------------------------------------------
;---------------------------------- Channel 1 ----------------------------------
;-------------------------------------------------------------------------------
gbt_channel_1_handle:: ; de = info
ld a,(gbt_channels_enabled)
and a,#0x01
jr nz,channel1_enabled$
; Channel is disabled. Increment pointer as needed
ld a,(de)
inc de
bit 7,a
jr nz,ch1_more_bytes$
bit 6,a
jr z,ch1_no_more_bytes_this_channel$
jr ch1_one_more_byte$
ch1_more_bytes$:
ld a,(de)
inc de
bit 7,a
jr z,ch1_no_more_bytes_this_channel$
ch1_one_more_byte$:
inc de
ch1_no_more_bytes_this_channel$:
ret
channel1_enabled$:
; Channel 1 is enabled
ld a,(de)
inc de
bit 7,a
jr nz,ch1_has_frequency$
; Not frequency
bit 6,a
jr nz,ch1_instr_effects$
; Set volume or NOP
bit 5,a
jr nz,ch1_just_set_volume$
; NOP
ret
ch1_just_set_volume$:
; Set volume
and a,#0x0F
swap a
; Preserve envelope data
ld b,a ; save byte
ld a,(gbt_vol+0)
and a,#0x0F ; mask envelope
or a,b
ld (gbt_vol+0),a
jr refresh_channel1_regs_trig$
ch1_instr_effects$:
; Set instrument and effect
ld b,a ; save byte
and a,#0x30
sla a
sla a
ld (gbt_instr+0),a ; Instrument
ld a,b ; restore byte
and a,#0x0F ; a = effect
call gbt_channel_1_set_effect
and a,a
ret z ; if 0, don't refresh registers
jr refresh_channel1_regs_notrig$
ch1_has_frequency$:
; Has frequency
and a,#0x7F
ld (gbt_arpeggio_freq_index+0*3),a
; This destroys hl and a. Returns freq in bc
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+0*2+0),a
ld a,b
ld (gbt_freq+0*2+1),a ; Get frequency
ld a,(de)
inc de
bit 7,a
jr nz,ch1_freq_instr_and_effect$
; Freq + Instr + Volume
ld b,a ; save byte
and a,#0x30
sla a
sla a
ld (gbt_instr+0),a ; Instrument
ld a,b ; restore byte
and a,#0x0F ; a = volume
swap a
; Preserve envelope data
ld b,a ; save byte
ld a,(gbt_vol+0)
and a,#0x0F ; mask envelope
or a,b
ld (gbt_vol+0),a
jr refresh_channel1_regs_trig$
ch1_freq_instr_and_effect$:
; Freq + Instr + Effect
ld b,a ; save byte
and a,#0x30
sla a
sla a
ld (gbt_instr+0),a ; Instrument
ld a,b ; restore byte
and a,#0x0F ; a = effect
call gbt_channel_1_set_effect
;jr refresh_channel1_regs_trig$
; fall through!
; -----------------
refresh_channel1_regs_trig$:
channel1_refresh_registers_trig:
xor a,a
ld (#.NR10),a
ld a,(gbt_instr+0)
ld (#.NR11),a
ld a,(gbt_vol+0)
ld (#.NR12),a
ld a,(gbt_freq+0*2+0)
ld (#.NR13),a
ld a,(gbt_freq+0*2+1)
or a,#0x80 ; start
ld (#.NR14),a
ret
refresh_channel1_regs_notrig$:
channel1_refresh_registers_notrig:
xor a,a
ld (#.NR10),a
ld a,(gbt_instr+0)
ld (#.NR11),a
ld a,(gbt_freq+0*2+0)
ld (#.NR13),a
ld a,(gbt_freq+0*2+1)
ld (#.NR14),a
ret
; ------------------
channel1_update_effects: ; returns 1 in a if it is needed to update sound registers
; Cut note
; --------
ld a,(gbt_cut_note_tick+0)
ld hl,#gbt_ticks_elapsed
cp a,(hl)
jp nz,ch1_dont_cut$
dec a ; a = 0xFF
ld (gbt_cut_note_tick+0),a ; disable cut note
xor a,a ; vol = 0
ld (#.NR12),a
ld a,#0x80 ; start
ld (#.NR14),a
ch1_dont_cut$:
; Arpeggio or Sweep
; --------
ld a,(gbt_arpeggio_enabled+0)
and a,a
ret z ; a is 0, return 0
; Check if Sweep or Arpeggio (4-5 cycles)
and a,#1
jr z,gbt_ch1_sweep_run$
; If enabled arpeggio, handle it
ld a,(gbt_arpeggio_tick+0)
and a,a
jr nz,ch1_not_tick_0$
; Tick 0 - Set original frequency
ld a,(gbt_arpeggio_freq_index+0*3+0)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+0*2+0),a
ld a,b
ld (gbt_freq+0*2+1),a ; Set frequency
ld a,#1
ld (gbt_arpeggio_tick+0),a
ret ; ret 1
ch1_not_tick_0$:
cp a,#1
jr nz,ch1_not_tick_1$
; Tick 1
ld a,(gbt_arpeggio_freq_index+0*3+1)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+0*2+0),a
ld a,b
ld (gbt_freq+0*2+1),a ; Set frequency
ld a,#2
ld (gbt_arpeggio_tick+0),a
dec a
ret ; ret 1
ch1_not_tick_1$:
; Tick 2
ld a,(gbt_arpeggio_freq_index+0*3+2)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+0*2+0),a
ld a,b
ld (gbt_freq+0*2+1),a ; Set frequency
xor a,a
ld (gbt_arpeggio_tick+0),a
inc a
ret ; ret 1
gbt_ch1_sweep_run$:
; PortA Pitch Sweep
; -----------
ld hl,#(gbt_freq+0*2+0)
ld a,(gbt_sweep+0)
bit 7,a ; bit 7, if nz, sweep up.
jr z,gbt_ch1_sweep_up$
; Sweep down -
sub a,#0x80
ld b,a
ld a,(hl) ; Get frequency small (gbt_freq+0*2+0)
sub a,b ; subtract b from a
ld (hl+),a ; Set frequency small (gbt_freq+0*2+0)
ld a,#1
jr c,gbt_ch1_sweep_dec$
ret ; ret 1, update without trigger
; Sweep down --
gbt_ch1_sweep_dec$:
dec (hl) ; DEC frequency large (gbt_freq+0*2+1) 3cy
ld a,(hl)
inc a ; find if decremented past 0 to exactly 255
ret nz ; ret/update unless 0
ld (hl-),a ; fix frequency large 0x0
ld (hl),a ; fix frequency small 0x0
ld (gbt_arpeggio_enabled+0),a ; disable sweep
ret ; ret 0, no update
; Sweep up +
gbt_ch1_sweep_up$:
add a,(hl) ; add frequency small (gbt_freq+0*2+0)
ld (hl+),a ; Set frequency small (gbt_freq+0*2+0)
jr c,gbt_ch1_sweep_inc$
ld a,#1
ret ; ret 1, update without trigger
; Sweep up ++
gbt_ch1_sweep_inc$:
inc (hl) ; inc frequency large (gbt_freq+0*2+1) 2cy
ld a,(hl-)
and a,#0x07 ; check if wrapped to 0x08 00001000
ret nz ; ret/update unless 0
ld (gbt_arpeggio_enabled+0),a ; disable sweep
ld (#.NR12),a ; vol = 0
ld a,#0x80 ; start
ld (#.NR14),a
ret ; ret 0x80, update without trigger
; -----------------
; returns a = 1 if needed to update registers, 0 if not
gbt_channel_1_set_effect: ; a = effect, de = pointer to data.
ld hl,#gbt_ch1_jump_table$
ld c,a
ld b,#0
add hl,bc
add hl,bc
ld a,(hl+)
ld h,(hl)
ld l,a
ld a,(de) ; load args
inc de
jp (hl)
gbt_ch1_jump_table$:
.DW gbt_ch1_pan$
.DW gbt_ch1_arpeggio$
.DW gbt_ch1_cut_note$
.DW gbt_ch1234_nop
.DW gbt_ch1_sweep$
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_jump_pattern
.DW gbt_ch1234_jump_position
.DW gbt_ch1234_speed
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1_NRx2_VolEnv$
gbt_ch1_pan$:
and a,#0x11
ld (gbt_pan+0),a
xor a,a
ret ; ret 0 do not update registers, only NR51 at end.
gbt_ch1_arpeggio$:
ld b,a ; b = params
ld hl,#gbt_arpeggio_freq_index+0*3
ld c,(hl) ; c = base index
inc hl
ld a,b
swap a
and a,#0x0F
add a,c
ld (hl+),a ; save first increment
ld a,b
and a,#0x0F
add a,c
ld (hl),a ; save second increment
ld a,#1
ld (gbt_arpeggio_enabled+0),a
ld (gbt_arpeggio_tick+0),a
ret ; ret 1
gbt_ch1_cut_note$:
ld (gbt_cut_note_tick+0),a
xor a,a ; ret 0
ret
gbt_ch1_NRx2_VolEnv$: ; Raw data into volume, VVVV APPP, bits 4-7 vol
ld (gbt_vol+0),a ; bit 3 true = add, bits 0-2 wait period
xor a,a ; ret 0 ; 0xF1 = max volume, sub 1 every 1 tick.
ret ; 0x0A = min volume, add 1 every 2 ticks.
gbt_ch1_sweep$:
ld (gbt_sweep+0),a
ld a,#2
ld (gbt_arpeggio_enabled+0),a
xor a,a ; ret 0
ret
;-------------------------------------------------------------------------------
;---------------------------------- Channel 2 ----------------------------------
;-------------------------------------------------------------------------------
gbt_channel_2_handle:: ; de = info
ld a,(gbt_channels_enabled)
and a,#0x02
jr nz,channel2_enabled$
; Channel is disabled. Increment pointer as needed
ld a,(de)
inc de
bit 7,a
jr nz,ch2_more_bytes$
bit 6,a
jr z,ch2_no_more_bytes_this_channel$
jr ch2_one_more_byte$
ch2_more_bytes$:
ld a,(de)
inc de
bit 7,a
jr z,ch2_no_more_bytes_this_channel$
ch2_one_more_byte$:
inc de
ch2_no_more_bytes_this_channel$:
ret
channel2_enabled$:
; Channel 2 is enabled
ld a,(de)
inc de
bit 7,a
jr nz,ch2_has_frequency$
; Not frequency
bit 6,a
jr nz,ch2_instr_effects$
; Set volume or NOP
bit 5,a
jr nz,ch2_just_set_volume$
; NOP
ret
ch2_just_set_volume$:
; Set volume
and a,#0x0F
swap a
; Preserve envelope data
ld b,a ; save byte
ld a,(gbt_vol+1)
and a,#0x0F ; mask envelope
or a,b
ld (gbt_vol+1),a
jr refresh_channel2_regs_trig$
ch2_instr_effects$:
; Set instrument and effect
ld b,a ; save byte
and a,#0x30
sla a
sla a
ld (gbt_instr+1),a ; Instrument
ld a,b ; restore byte
and a,#0x0F ; a = effect
call gbt_channel_2_set_effect
and a,a
ret z ; if 0, don't refresh registers
jr refresh_channel2_regs_notrig$
ch2_has_frequency$:
; Has frequency
and a,#0x7F
ld (gbt_arpeggio_freq_index+1*3),a
; This destroys hl and a. Returns freq in bc
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+1*2+0),a
ld a,b
ld (gbt_freq+1*2+1),a ; Get frequency
ld a,(de)
inc de
bit 7,a
jr nz,ch2_freq_instr_and_effect$
; Freq + Instr + Volume
ld b,a ; save byte
and a,#0x30
sla a
sla a
ld (gbt_instr+1),a ; Instrument
ld a,b ; restore byte
and a,#0x0F ; a = volume
swap a
; Preserve envelope data
ld b,a ; save byte
ld a,(gbt_vol+1)
and a,#0x0F ; mask envelope
or a,b
ld (gbt_vol+1),a
jr refresh_channel2_regs_trig$
ch2_freq_instr_and_effect$:
; Freq + Instr + Effect
ld b,a ; save byte
and a,#0x30
sla a
sla a
ld (gbt_instr+1),a ; Instrument
ld a,b ; restore byte
and a,#0x0F ; a = effect
call gbt_channel_2_set_effect
;jr .refresh_channel2_regs_trig
; fall through!
; -----------------
refresh_channel2_regs_trig$:
channel2_refresh_registers_trig:
ld a,(gbt_instr+1)
ld (#.NR21),a
ld a,(gbt_vol+1)
ld (#.NR22),a
ld a,(gbt_freq+1*2+0)
ld (#.NR23),a
ld a,(gbt_freq+1*2+1)
or a,#0x80 ; start
ld (#.NR24),a
ret
refresh_channel2_regs_notrig$:
channel2_refresh_registers_notrig:
ld a,(gbt_instr+1)
ld (#.NR21),a
ld a,(gbt_freq+1*2+0)
ld (#.NR23),a
ld a,(gbt_freq+1*2+1)
ld (#.NR24),a
ret
; ------------------
channel2_update_effects: ; returns 1 in a if it is needed to update sound regs
; Cut note
; --------
ld a,(gbt_cut_note_tick+1)
ld hl,#gbt_ticks_elapsed
cp a,(hl)
jp nz,ch2_dont_cut$
dec a ; a = 0xFF
ld (gbt_cut_note_tick+1),a ; disable cut note
xor a,a ; vol = 0
ld (#.NR22),a
ld a,#0x80 ; start
ld (#.NR24),a
ch2_dont_cut$:
; Arpeggio or Sweep
; --------
ld a,(gbt_arpeggio_enabled+1)
and a,a
ret z ; a is 0, return 0
; Check if Sweep or Arpeggio (5-6 cycles)
and a,#1
jr z,gbt_ch2_sweep_run$
; If enabled arpeggio, handle it
ld a,(gbt_arpeggio_tick+1)
and a,a
jr nz,ch2_not_tick_0$
; Tick 0 - Set original frequency
ld a,(gbt_arpeggio_freq_index+1*3+0)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+1*2+0),a
ld a,b
ld (gbt_freq+1*2+1),a ; Set frequency
ld a,#1
ld (gbt_arpeggio_tick+1),a
ret ; ret 1
ch2_not_tick_0$:
cp a,#1
jr nz,ch2_not_tick_1$
; Tick 1
ld a,(gbt_arpeggio_freq_index+1*3+1)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+1*2+0),a
ld a,b
ld (gbt_freq+1*2+1),a ; Set frequency
ld a,#2
ld (gbt_arpeggio_tick+1),a
dec a
ret ; ret 1
ch2_not_tick_1$:
; Tick 2
ld a,(gbt_arpeggio_freq_index+1*3+2)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+1*2+0),a
ld a,b
ld (gbt_freq+1*2+1),a ; Set frequency
xor a,a
ld (gbt_arpeggio_tick+1),a
inc a
ret ; ret 1
gbt_ch2_sweep_run$:
; PortA Pitch Sweep
; -----------
ld hl,#(gbt_freq+1*2+0)
ld a,(gbt_sweep+1)
bit 7,a ; bit 7, if nz, sweep up.
jr z,gbt_ch2_sweep_up$
; Sweep down -
sub a,#0x80
ld b,a
ld a,(hl) ; Get frequency small (gbt_freq+0*2+0)
sub a,b ; subtract b from a
ld (hl+),a ; Set frequency small (gbt_freq+0*2+0)
ld a,#1
jr c,gbt_ch2_sweep_dec$
ret ; ret 1, update without trigger
; Sweep down --
gbt_ch2_sweep_dec$:
dec (hl) ; DEC frequency large (gbt_freq+0*2+1) 3cy
ld a,(hl)
inc a ; find if decremented past 0 to exactly 255
ret nz ; ret/update unless 0
ld (hl-),a ; fix frequency large 0x0
ld (hl),a ; fix frequency small 0x0
ld (gbt_arpeggio_enabled+1),a ; disable sweep
ret ; ret 0, no update
; Sweep up +
gbt_ch2_sweep_up$:
add a,(hl) ; add frequency small (gbt_freq+0*2+0)
ld (hl+),a ; Set frequency small (gbt_freq+0*2+0)
jr c,gbt_ch2_sweep_inc$
ld a,#1
ret ; ret 1, update without trigger
; Sweep up ++
gbt_ch2_sweep_inc$:
inc (hl) ; inc frequency large (gbt_freq+0*2+1) 2cy
ld a,(hl-)
and a,#0x07 ; check if wrapped to 0x08 00001000
ret nz ; ret/update unless 0
ld (gbt_arpeggio_enabled+1),a ; disable sweep
ld (#.NR22),a ; vol = 0
ld a,#0x80 ; start
ld (#.NR24),a
ret ; ret 0x80, update without trigger
; -----------------
; returns a = 1 if needed to update registers, 0 if not
gbt_channel_2_set_effect: ; a = effect, de = pointer to data
ld hl,#gbt_ch2_jump_table$
ld c,a
ld b,#0
add hl,bc
add hl,bc
ld a,(hl+)
ld h,(hl)
ld l,a
ld a,(de) ; load args
inc de
jp (hl)
gbt_ch2_jump_table$:
.DW gbt_ch2_pan$
.DW gbt_ch2_arpeggio$
.DW gbt_ch2_cut_note$
.DW gbt_ch1234_nop
.DW gbt_ch2_sweep$
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_jump_pattern
.DW gbt_ch1234_jump_position
.DW gbt_ch1234_speed
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch2_NRx2_VolEnv$
gbt_ch2_pan$:
and a,#0x22
ld (gbt_pan+1),a
xor a,a ; ret 0
ret ; Should not update registers, only NR51 at end.
gbt_ch2_arpeggio$:
ld b,a ; b = params
ld hl,#gbt_arpeggio_freq_index+1*3
ld c,(hl) ; c = base index
inc hl
ld a,b
swap a
and a,#0x0F
add a,c
ld (hl+),a ; save first increment
ld a,b
and a,#0x0F
add a,c
ld (hl),a ; save second increment
ld a,#1
ld (gbt_arpeggio_enabled+1),a
ld (gbt_arpeggio_tick+1),a
ret ; ret 1
gbt_ch2_cut_note$:
ld (gbt_cut_note_tick+1),a
xor a,a ; ret 0
ret
gbt_ch2_NRx2_VolEnv$: ; raw volumeEnv, VVVV APPP, bits 7-4 vol
ld (gbt_vol+1),a ; bit 3 true = add, bits 2-0 wait period
xor a,a ; ret 0 ; 0xF1 = max volume, sub 1 every 1 tick.
ret ; 0x0A = min volume, add 1 every 2 ticks.
gbt_ch2_sweep$:
ld (gbt_sweep+1),a
ld a,#2
ld (gbt_arpeggio_enabled+1),a
xor a,a ; ret 0
ret
;-------------------------------------------------------------------------------
;---------------------------------- Channel 3 ----------------------------------
;-------------------------------------------------------------------------------
gbt_channel_3_handle:: ; de = info
ld a,(gbt_channels_enabled)
and a,#0x04
jr nz,channel3_enabled$
; Channel is disabled. Increment pointer as needed
ld a,(de)
inc de
bit 7,a
jr nz,ch3_more_bytes$
bit 6,a
jr z,ch3_no_more_bytes_this_channel$
jr ch3_one_more_byte$
ch3_more_bytes$:
ld a,(de)
inc de
bit 7,a
jr z,ch3_no_more_bytes_this_channel$
ch3_one_more_byte$:
inc de
ch3_no_more_bytes_this_channel$:
ret
channel3_enabled$:
; Channel 3 is enabled
ld a,(de)
inc de
bit 7,a
jr nz,ch3_has_frequency$
; Not frequency
bit 6,a
jr nz,ch3_effects$
; Set volume or NOP
bit 5,a
jr nz,ch3_just_set_volume$
; NOP
ret
ch3_just_set_volume$:
; Set volume
swap a
ld (gbt_vol+2),a
jr refresh_channel3_regs_trig$
ch3_effects$:
; Set effect
and a,#0x0F ; a = effect
call gbt_channel_3_set_effect
and a,a
ret z ; if 0, don't refresh registers
jr refresh_channel3_regs_notrig$
ch3_has_frequency$:
; Has frequency
and a,#0x7F
ld (gbt_arpeggio_freq_index+2*3),a
; This destroys hl and a. Returns freq in bc
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+2*2+0),a
ld a,b
ld (gbt_freq+2*2+1),a ; Get frequency
ld a,(de)
inc de
bit 7,a
jr nz,ch3_freq_instr_and_effect$
; Freq + Instr + Volume
ld b,a ; save byte
and a,#0x0F
ld (gbt_instr+2),a ; Instrument
ld a,b ; restore byte
and a,#0x30 ; a = volume
sla a
ld (gbt_vol+2),a
jr refresh_channel3_regs_trig$
ch3_freq_instr_and_effect$:
; Freq + Instr + Effect
ld b,a ; save byte
and a,#0x0F
ld (gbt_instr+2),a ; Instrument
ld a,b ; restore byte
and a,#0x70
swap a ; a = effect (only 0-7 allowed here)
call gbt_channel_3_set_effect
;jr .refresh_channel3_regs
; fall through!
; -----------------
refresh_channel3_regs_trig$:
channel3_refresh_registers_trig:
xor a,a
ld (#.NR30),a ; disable
ld a,(gbt_channel3_loaded_instrument)
ld b,a
ld a,(gbt_instr+2)
cp a,b
call nz,gbt_channel3_load_instrument ; a = instrument
ld a,#0x80
ld (#.NR30),a ; enable
xor a,a
ld (#.NR31),a
ld a,(gbt_vol+2)
ld (#.NR32),a
ld a,(gbt_freq+2*2+0)
ld (#.NR33),a
ld a,(gbt_freq+2*2+1)
or a,#0x80 ; start
ld (#.NR34),a
ret
refresh_channel3_regs_notrig$:
; Don't Restart Waveform!
channel3_refresh_registers_notrig:
ld a,(gbt_freq+2*2+0)
ld (#.NR33),a
ld a,(gbt_freq+2*2+1)
ld (#.NR34),a
ret
; ------------------
gbt_channel3_load_instrument:
ld (gbt_channel3_loaded_instrument),a
swap a ; a = a * 16
ld c,a
ld b,#0
ld hl,#gbt_wave
add hl,bc
ld c,#0x30
ld b,#16
ch3_loop$:
ld a,(hl+)
ldh (c),a
inc c
dec b
jr nz,ch3_loop$
ret
; ------------------
channel3_update_effects: ; returns 1 in a if it is needed to update sound regs
; Cut note
; --------
ld a,(gbt_cut_note_tick+2)
ld hl,#gbt_ticks_elapsed
cp a,(hl)
jp nz,ch3_dont_cut$
dec a ; a = 0xFF
ld (gbt_cut_note_tick+2),a ; disable cut note
xor a,a ; vol = 0
ld (#.NR30),a ; disable
ld (#.NR32),a
ld a,#0x80 ; start
ld (#.NR34),a
ch3_dont_cut$:
; Arpeggio or Sweep
; --------
ld a,(gbt_arpeggio_enabled+2)
and a,a
ret z ; a is 0, return 0
; Check if Sweep or Arpeggio (5-6 cycles)
and a,#1
jp z,gbt_ch3_sweep_run$
; If enabled arpeggio, handle it
ld a,(gbt_arpeggio_tick+2)
and a,a
jr nz,ch3_not_tick_0$
; Tick 0 - Set original frequency
ld a,(gbt_arpeggio_freq_index+2*3+0)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+2*2+0),a
ld a,b
ld (gbt_freq+2*2+1),a ; Set frequency
ld a,#1
ld (gbt_arpeggio_tick+2),a
ret ; ret 1
ch3_not_tick_0$:
cp a,#1
jr nz,ch3_not_tick_1$
; Tick 1
ld a,(gbt_arpeggio_freq_index+2*3+1)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+2*2+0),a
ld a,b
ld (gbt_freq+2*2+1),a ; Set frequency
ld a,#2
ld (gbt_arpeggio_tick+2),a
dec a
ret ; ret 1
ch3_not_tick_1$:
; Tick 2
ld a,(gbt_arpeggio_freq_index+2*3+2)
call _gbt_get_freq_from_index
ld a,c
ld (gbt_freq+2*2+0),a
ld a,b
ld (gbt_freq+2*2+1),a ; Set frequency
xor a,a
ld (gbt_arpeggio_tick+2),a
inc a
ret ; ret 1
gbt_ch3_sweep_run$:
; PortA Pitch Sweep
; -----------
ld hl,#(gbt_freq+2*2+0)
ld a,(gbt_sweep+2)
bit 7,a ; bit 7, if nz, sweep up.
jr z,gbt_ch3_sweep_up$
; Sweep down -
sub a,#0x80
ld b,a
ld a,(hl) ; Get frequency small (gbt_freq+0*2+0)
sub a,b ; subtract b from a
ld (hl+),a ; Set frequency small (gbt_freq+0*2+0)
ld a,#1
jr c,gbt_ch3_sweep_dec$
ret ; ret 1, update without trigger
; Sweep down --
gbt_ch3_sweep_dec$:
dec (hl) ; DEC frequency large (gbt_freq+0*2+1) 3cy
ld a,(hl)
inc a ; find if decremented past 0 to exactly 255
ret nz ; ret/update unless 0
ld (hl-),a ; fix frequency large 0x0
ld (hl),a ; fix frequency small 0x0
ld (gbt_arpeggio_enabled+2),a ; disable sweep
ret ; ret 0, no update
; Sweep up +
gbt_ch3_sweep_up$:
add a,(hl) ; add frequency small (gbt_freq+0*2+0)
ld (hl+),a ; Set frequency small (gbt_freq+0*2+0)
jr c,gbt_ch3_sweep_inc$
ld a,#1
ret ; ret 1, update without trigger
; Sweep up ++
gbt_ch3_sweep_inc$:
inc (hl) ; inc frequency large (gbt_freq+0*2+1) 2cy
ld a,(hl-)
and a,#0x07 ; check if wrapped to 0x08 00001000
ret nz ; ret/update unless 0
ld (gbt_arpeggio_enabled+2),a ; disable sweep
ld (#.NR32),a ; vol = 0
ld a,#0x80 ; start
ld (#.NR34),a
ret ; ret 1, update without trigger
; -----------------
; returns a = 1 if needed to update registers, 0 if not
gbt_channel_3_set_effect: ; a = effect, de = pointer to data
ld hl,#gbt_ch3_jump_table$
ld c,a
ld b,#0
add hl,bc
add hl,bc
ld a,(hl+)
ld h,(hl)
ld l,a
ld a,(de) ; load args
inc de
jp (hl)
gbt_ch3_jump_table$:
.DW gbt_ch3_pan$
.DW gbt_ch3_arpeggio$
.DW gbt_ch3_cut_note$
.DW gbt_ch1234_nop
.DW gbt_ch3_sweep$
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_jump_pattern
.DW gbt_ch1234_jump_position
.DW gbt_ch1234_speed
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
gbt_ch3_pan$:
and a,#0x44
ld (gbt_pan+2),a
xor a,a ; ret 0
ret ; do not update registers, only NR51 at end.
gbt_ch3_arpeggio$:
ld b,a ; b = params
ld hl,#gbt_arpeggio_freq_index+2*3
ld c,(hl) ; c = base index
inc hl
ld a,b
swap a
and a,#0x0F
add a,c
ld (hl+),a ; save first increment
ld a,b
and a,#0x0F
add a,c
ld (hl),a ; save second increment
ld a,#1
ld (gbt_arpeggio_enabled+2),a
ld (gbt_arpeggio_tick+2),a
ret ; ret 1
gbt_ch3_cut_note$:
ld (gbt_cut_note_tick+2),a
xor a,a ; ret 0
ret
gbt_ch3_sweep$:
ld (gbt_sweep+2),a
ld a,#2
ld (gbt_arpeggio_enabled+2),a
xor a,a ; ret 0
ret
;-------------------------------------------------------------------------------
;---------------------------------- Channel 4 ----------------------------------
;-------------------------------------------------------------------------------
gbt_channel_4_handle:: ; de = info
ld a,(gbt_channels_enabled)
and a,#0x08
jr nz,channel4_enabled$
; Channel is disabled. Increment pointer as needed
ld a,(de)
inc de
bit 7,a
jr nz,ch4_more_bytes$
bit 6,a
jr z,ch4_no_more_bytes_this_channel$
jr ch4_one_more_byte$
ch4_more_bytes$:
ld a,(de)
inc de
bit 7,a
jr z,ch4_no_more_bytes_this_channel$
ch4_one_more_byte$:
inc de
ch4_no_more_bytes_this_channel$:
ret
channel4_enabled$:
; Channel 4 is enabled
ld a,(de)
inc de
bit 7,a
jr nz,ch4_has_instrument$
; Not instrument
bit 6,a
jr nz,ch4_effects$
; Set volume or NOP
bit 5,a
jr nz,ch4_just_set_volume$
; NOP
ret
ch4_just_set_volume$:
; Set volume
and a,#0x0F
swap a
; Preserve envelope data
ld b,a ; save byte
ld a,(gbt_vol+3)
and a,#0x0F ; mask envelope
or a,b
ld (gbt_vol+3),a
jr refresh_channel4_regs$
ch4_effects$:
; Set effect
and a,#0x0F ; a = effect
call gbt_channel_4_set_effect
and a,a
ret z ; if 0, don't refresh registers
jr refresh_channel4_regs$
ch4_has_instrument$:
; Has instrument raw frequency data
and a,#0x7F ; mask out bit 7
ld b,a
ld a,(de) ; load next byte
inc de
ld c,a
rla
and a,#0x80 ; Mask only bit 7
or a,b ; Append noise bit
ld (gbt_instr+3),a
ld a,c ; restore byte2
bit 7,a
jr nz,ch4_instr_and_effect$
; Instr + Volume
and a,#0x0F ; a = volume
swap a
; Preserve envelope data
ld b,a ; save byte
ld a,(gbt_vol+3)
and a,#0x0F ; mask envelope
or a,b
ld (gbt_vol+3),a
jr refresh_channel4_regs$
ch4_instr_and_effect$:
; Instr + Effect
and a,#0x0F ; a = effect
call gbt_channel_4_set_effect
;jr ch4_refresh_channel4_regs$
refresh_channel4_regs$:
; fall through!
; -----------------
channel4_refresh_registers:
xor a,a
ld (#.NR41),a
ld a,(gbt_vol+3)
ld (#.NR42),a
ld a,(gbt_instr+3)
ld (#.NR43),a
ld a,#0x80 ; start
ld (#.NR44),a
ret
; ------------------
channel4_update_effects: ; returns 1 in a if it is needed to update sound regs
; Cut note
; --------
ld a,(gbt_cut_note_tick+3)
ld hl,#gbt_ticks_elapsed
cp a,(hl)
jp nz,ch4_dont_cut$
dec a ; a = 0xFF
ld (gbt_cut_note_tick+3),a ; disable cut note
xor a,a ; vol = 0
ld (#.NR42),a
ld a,#0x80 ; start
ld (#.NR44),a
ch4_dont_cut$:
xor a,a
ret ; a is 0, return
; -----------------
; returns a = 1 if needed to update registers, 0 if not
gbt_channel_4_set_effect: ; a = effect, de = pointer to data
ld hl,#gbt_ch4_jump_table$
ld c,a
ld b,#0
add hl,bc
add hl,bc
ld a,(hl+)
ld h,(hl)
ld l,a
ld a,(de) ; load args
inc de
jp (hl)
gbt_ch4_jump_table$:
.DW gbt_ch4_pan$
.DW gbt_ch1234_nop ; gbt_ch4_arpeggio
.DW gbt_ch4_cut_note$
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_jump_pattern
.DW gbt_ch1234_jump_position
.DW gbt_ch1234_speed
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch1234_nop
.DW gbt_ch4_NRx2_VolEnv$
gbt_ch4_pan$:
and a,#0x88
ld (gbt_pan+3),a
xor a,a ; ret 0
ret ; do not update registers, only NR51 at end.
gbt_ch4_cut_note$:
ld (gbt_cut_note_tick+3),a
xor a,a ; ret 0
ret
gbt_ch4_NRx2_VolEnv$: ; Raw data into volume, VVVV APPP, bits 4-7 vol
ld (gbt_vol+3),a ; bit 3 true = add, bits 0-2 wait period
xor a,a ; ret 0 ; 0xF1 = max volume, sub 1 every 1 tick.
ret ; 0x0A = min volume, add 1 every 2 ticks.
;-------------------------------------------------------------------------------
; Common effects go here:
gbt_ch1234_nop:
xor a,a ;ret 0
ret
gbt_ch1234_jump_pattern:
ld (gbt_current_pattern),a
xor a,a
ld (gbt_current_step),a
ld (gbt_have_to_stop_next_step),a ; clear stop flag
ld a,#1
ld (gbt_update_pattern_pointers),a
xor a,a ;ret 0
ret
gbt_ch1234_jump_position:
ld (gbt_current_step),a
ld hl,#gbt_current_pattern
inc (hl)
; Check to see if jump puts us past end of song
ld a,(hl)
call gbt_get_pattern_ptr_banked
ld a,#1 ; tell gbt_player.s to do this next cycle
ld (gbt_update_pattern_pointers),a
xor a,a ;ret 0
ret
gbt_ch1234_speed:
ld (gbt_speed),a
xor a,a
ld (gbt_ticks_elapsed),a
ret ;ret 0
;-------------------------------------------------------------------------------
gbt_update_bank1::
ld de,#gbt_temp_play_data
; each function will return in de the pointer to next byte
call gbt_channel_1_handle
call gbt_channel_2_handle
call gbt_channel_3_handle
call gbt_channel_4_handle
; end of channel handling
ld hl,#gbt_pan
ld a,(hl+)
or a,(hl)
inc hl
or a,(hl)
inc hl
or a,(hl)
ld (#.NR51),a ; handle panning...
ret
;-------------------------------------------------------------------------------
gbt_update_effects_bank1::
call channel1_update_effects
and a,a
call nz,channel1_refresh_registers_notrig
call channel2_update_effects
and a,a
call nz,channel2_refresh_registers_notrig
call channel3_update_effects
and a,a
call nz,channel3_refresh_registers_notrig
call channel4_update_effects
and a,a
call nz,channel4_refresh_registers
ret
;-------------------------------------------------------------------------------