My 6502 skills are unfortunately rather rusty, so I can't understand your drum code at a quick glance, but the drum data seems to be off. The kick drum PWM period should double every 4 half-cycles. The hat data probably needs to be longer for the result to sound somewhat like white noise.
]]>Drums are very off compared to the Z80, and the pitch still needs some work.
You can see the current progress here:
https://m.youtube.com/watch?v=W1Br7rr8cps
If you’re interested in the code (and can help eliminating bugs / inconsistencies / misinterpretations) this is what I have so far (BeebAsm format for the BBC Micro):
VIA_DDRA = $FE43
VIA_DDRB = $FE42
VIA_ORA = $FE41
VIA_ORB = $FE40
SN_LOUD = $90
SN_MUTE = $9F
SAMPLES_PER_FRAME = 260
SAMPLES_LO = SAMPLES_PER_FRAME AND 255
SAMPLES_HI = SAMPLES_PER_FRAME DIV 256
ORG 0
.seq_ptr SKIP 2
.row_timer SKIP 1
.sample_count SKIP 2
.tmp_mix SKIP 1
.ctrl_a SKIP 1
.ctrl_b SKIP 1
.pat_ptr SKIP 2
.drum_flag SKIP 1
.drum_index SKIP 1
.drum_delay SKIP 1
.drum_state SKIP 1
.ch1_f SKIP 2
.ch1_a SKIP 2
.ch1_e SKIP 2
.ch1_d SKIP 1
.ch1_n SKIP 1
.ch2_f SKIP 2
.ch2_a SKIP 2
.ch2_e SKIP 2
.ch2_d SKIP 1
.ch2_n SKIP 1
.ch3_f SKIP 2
.ch3_a SKIP 2
.ch3_e SKIP 2
.ch3_d SKIP 1
.ch4_f SKIP 2
.ch4_a SKIP 2
.ch4_e SKIP 2
.ch4_d SKIP 1
.ch4_s SKIP 1
ORG $1100
.start
SEI
JSR init_hw
LDA #LO(music_data+2)
STA seq_ptr
LDA #HI(music_data+2)
STA seq_ptr+1
JSR fetch_new_pattern
JMP check_row
.pattern_end
LDA seq_ptr
CLC
ADC #2
STA seq_ptr
BCC p_next
INC seq_ptr+1
.p_next
LDY #0
LDA (seq_ptr),Y
STA pat_ptr
INY
LDA (seq_ptr),Y
STA pat_ptr+1
LDA pat_ptr
ORA pat_ptr+1
BNE check_row
LDA music_data
STA seq_ptr
LDA music_data+1
STA seq_ptr+1
JMP pattern_end
.check_row
LDY #0
LDA (pat_ptr),Y
CMP #$40
BEQ pattern_end
.rdseq
LDA (pat_ptr),Y
INY
STA ctrl_a
LDA (pat_ptr),Y
INY
STA row_timer
LDA (pat_ptr),Y
STA ch2_n
INY
LDA (pat_ptr),Y
STA ch1_n
INY
LDA ctrl_a
LSR A
BCS ld2
LDA (pat_ptr),Y
STA ch1_f
INY
LDA (pat_ptr),Y
STA ch1_f+1
INY
LDA (pat_ptr),Y
STA ch1_e
INY
LDA (pat_ptr),Y
STA ch1_e+1
INY
LDA #0
STA ch1_a
STA ch1_a+1
STY tmp_mix
LDY #0
LDA (ch1_e),Y
STA ch1_d
LDY tmp_mix
.ld2
LDA ctrl_a
AND #4
BNE ld3
LDA (pat_ptr),Y
STA ch2_f
INY
LDA (pat_ptr),Y
STA ch2_f+1
INY
LDA (pat_ptr),Y
STA ch2_e
INY
LDA (pat_ptr),Y
STA ch2_e+1
INY
LDA #0
STA ch2_a
STA ch2_a+1
STY tmp_mix
LDY #0
LDA (ch2_e),Y
STA ch2_d
LDY tmp_mix
.ld3
BIT ctrl_a
BMI ld4
LDA (pat_ptr),Y
STA ch3_f
INY
LDA (pat_ptr),Y
STA ch3_f+1
INY
LDA (pat_ptr),Y
STA ch3_e
INY
LDA (pat_ptr),Y
STA ch3_e+1
INY
LDA #0
STA ch3_a
STA ch3_a+1
STY tmp_mix
LDY #0
LDA (ch3_e),Y
STA ch3_d
LDY tmp_mix
.ld4
LDA (pat_ptr),Y
STA ctrl_b
INY
INY
LDA #0
STA drum_flag
LDA ctrl_b
AND #$04
BEQ no_kick
LDA #1
STA drum_flag
LDA #0
STA drum_index
STA drum_delay
LDA #SN_MUTE
STA drum_state
.no_kick
LDA ctrl_b
AND #$80
BEQ no_hat
LDA #2
STA drum_flag
LDA #0
STA drum_index
STA drum_delay
LDA #SN_MUTE
STA drum_state
.no_hat
LDA ctrl_b
AND #$40
BNE skip4
LDA (pat_ptr),Y
STA ch4_f
INY
LDA (pat_ptr),Y
STA ch4_f+1
INY
LDA (pat_ptr),Y
STA ch4_e
INY
LDA (pat_ptr),Y
STA ch4_e+1
INY
LDA #0
STA ch4_a
STA ch4_a+1
STY tmp_mix
LDY #0
LDA (ch4_e),Y
STA ch4_d
LDY tmp_mix
.skip4
LDA ctrl_b
AND #1
STA ch4_s
TYA
CLC
ADC pat_ptr
STA pat_ptr
BCC p_adv
INC pat_ptr+1
.p_adv
LDA ch1_n
BEQ ch1_no_noise_smc
LDA #$6A
STA ch1_noise_op
LDA #$EA
STA ch1_noise_op+1
JMP ch2_smc
.ch1_no_noise_smc
LDA #$EA
STA ch1_noise_op
STA ch1_noise_op+1
.ch2_smc
LDA ch2_n
BEQ ch2_no_noise_smc
LDA #$6A
STA ch2_noise_op
LDA #$EA
STA ch2_noise_op+1
JMP start_synth
.ch2_no_noise_smc
LDA #$EA
STA ch2_noise_op
STA ch2_noise_op+1
.start_synth
LDA #SAMPLES_LO
STA sample_count
LDA #SAMPLES_HI
STA sample_count+1
CLC
.synth_loop
LDA #0
STA tmp_mix
\ Channel 1
LDA ch1_a
ADC ch1_f
STA ch1_a
LDA ch1_a+1
ADC ch1_f+1
STA ch1_a+1
.ch1_noise_op
NOP
NOP
ADC ch1_d
ROL tmp_mix
\ Channel 2
LDA ch2_a
ADC ch2_f
STA ch2_a
LDA ch2_a+1
ADC ch2_f+1
STA ch2_a+1
.ch2_noise_op
NOP
NOP
ADC ch2_d
ROL tmp_mix
\ Channel 3
LDA ch3_a
ADC ch3_f
STA ch3_a
LDA ch3_a+1
ADC ch3_f+1
STA ch3_a+1
ADC ch3_d
ROL tmp_mix
\ Channel 4
LDA ch4_a
ADC ch4_f
STA ch4_a
LDA ch4_a+1
ADC ch4_f+1
STA ch4_a+1
ADC ch4_d
ROL tmp_mix
LDA tmp_mix
ADC #$0F
TAX
CPX #$10
LDA #SN_MUTE
BCS vol_set
LDA #SN_LOUD
.vol_set
TAY
LDX drum_flag
BEQ output_no_drum
LDX drum_delay
BEQ need_new_sample
DEC drum_delay
LDA drum_state
JMP mix_tone_drum
.need_new_sample
LDX drum_flag
DEX
BEQ need_load_kick
DEX
BEQ need_load_hat
LDA drum_state
JMP mix_tone_drum
.need_load_kick
LDX drum_index
CPX #20
BCS need_kick_end
LDA kick_data,X
STA drum_delay
INC drum_index
LDA drum_state
EOR #$0F
STA drum_state
JMP mix_tone_drum
.need_kick_end
LDA #0
STA drum_flag
STA drum_delay
LDA drum_state
JMP mix_tone_drum
.need_load_hat
LDX drum_index
CPX #20
BCS need_hat_end
LDA hat_data,X
STA drum_delay
INC drum_index
LDA drum_state
EOR #$0F
STA drum_state
JMP mix_tone_drum
.need_hat_end
LDA #0
STA drum_flag
STA drum_delay
LDA drum_state
JMP mix_tone_drum
.output_no_drum
TYA
STA VIA_ORA
LDA #0
STA VIA_ORB
LDA #8
STA VIA_ORB
JMP sample_decrement
\ Mix tone and drum
.mix_tone_drum
STA ctrl_a
CPY #SN_LOUD
BNE drum_only
CMP #SN_LOUD
BNE tone_only
LDA #$98
JMP output_mixed
.drum_only
LDA ctrl_a
JMP output_mixed
.tone_only
TYA
.output_mixed
STA VIA_ORA
LDA #0
STA VIA_ORB
LDA #8
STA VIA_ORB
.sample_decrement
LDA sample_count
BNE dec_lo
DEC sample_count+1
.dec_lo
DEC sample_count
LDA sample_count
ORA sample_count+1
BEQ update_timer
JMP synth_loop
.update_timer
LDY #0
INC ch1_e
BNE e1
INC ch1_e+1
.e1
LDA (ch1_e),Y
CMP #$80
BEQ e2
STA ch1_d
.e2
INC ch2_e
BNE e2_skip
INC ch2_e+1
.e2_skip
LDA (ch2_e),Y
CMP #$80
BEQ e3
STA ch2_d
.e3
INC ch3_e
BNE e3_skip
INC ch3_e+1
.e3_skip
LDA (ch3_e),Y
CMP #$80
BEQ e4
STA ch3_d
.e4
INC ch4_e
BNE e4_skip
INC ch4_e+1
.e4_skip
LDA (ch4_e),Y
CMP #$80
BEQ slide_proc
STA ch4_d
.slide_proc
LDA ch4_s
BEQ noslide
LDA ch4_f+1
LSR A
TAX
LDA ch4_f
ROR A
TAY
SEC
LDA ch4_f
STY tmp_mix
SBC tmp_mix
STA ch4_f
LDA ch4_f+1
STX tmp_mix
SBC tmp_mix
STA ch4_f+1
.noslide
DEC row_timer
BNE play_same_row
JMP check_row
.play_same_row
LDA #SAMPLES_LO
STA sample_count
LDA #SAMPLES_HI
STA sample_count+1
CLC
JMP synth_loop
.fetch_new_pattern
LDY #0
LDA (seq_ptr),Y
STA pat_ptr
INY
LDA (seq_ptr),Y
STA pat_ptr+1
LDA pat_ptr
ORA pat_ptr+1
BNE fetch_done
LDA music_data
STA seq_ptr
LDA music_data+1
STA seq_ptr+1
JMP fetch_new_pattern
.fetch_done
RTS
.kick_data
EQUB 1,1,1,1,2,2,2,2
EQUB 3,3,3,4,4,4,5,5
EQUB 6,6,7,7
.hat_data
EQUB 16,3,12,6,9
EQUB 20,4,8,2,14
EQUB 9,17,5,8,12
EQUB 4,7,16,13,22
EQUB 5,3,16,3,12
.init_hw
LDA #$9F
JSR sn_w
LDA #$BF
JSR sn_w
LDA #$DF
JSR sn_w
LDA #$FF
JSR sn_w
LDA #$FF
STA VIA_DDRA
LDA #$0F
STA VIA_DDRB
LDA #$81
JSR sn_w
LDA #$00
JSR sn_w
RTS
.sn_w
STA VIA_ORA
LDX #0
STX VIA_ORB
LDX #8
STX VIA_ORB
RTS
ORG $2000
INCLUDE "tracks\Squeeker Plus\1-bit_high_and_rising.asm"
.end
SAVE "MAIN",start,end