bass and loop in asm

This commit is contained in:
Joachim Fenkes 2012-08-11 13:03:26 +02:00
parent 5f96c41f5f
commit db7376f914
2 changed files with 127 additions and 5 deletions

14
avr/Makefile Normal file
View file

@ -0,0 +1,14 @@
all: flash
noiseplug.elf: noiseplug.S
avr-gcc -Os -nostdlib -mmcu=attiny9 -o $@ $<
noiseplug.hex: noiseplug.elf
avr-objcopy -O ihex $< $@
flash: noiseplug.hex
avrdude -cavrisp2 -Pusb -pt8 -Uflash:w:$<:a
dump: noiseplug.elf
avr-objdump -Sr $< | less

View file

@ -25,7 +25,8 @@ PINB = 0x00
.comm bassosc, 2
.comm bassflange, 2
.comm arposc, 2
; leaves 10 bytes for stack
.comm boost, 1
; leaves 9 bytes for stack
.section .text
@ -51,6 +52,14 @@ __vector_4:
.size __vector_4, .-__vector_4
main_cont:
clr r31
ldi r30, 0x40
clearsram:
st Z+, r16
sbrs r30, 5
rjmp clearsram
out CCP, r17
out CLKPSR, r16
ldi r17, 5
@ -67,6 +76,7 @@ main_cont:
mainloop:
sleep
clr r16
lds r17, int_ctr
tst r17
brne mainloop
@ -77,15 +87,113 @@ mainloop:
lds r18, i+1
lds r19, i+2
subi r19, -1
sbci r18, 0
sbci r17, 0
subi r19, 0xff
sbci r18, 0xff
sbci r17, 0xff
; if ((i >> 13) == 76) i = 16 << 13;
mov r20, r18
rol r20
mov r20, r17
rol r20
subi r20, 0x13
brne norestart
ldi r17, 2
clr r18
norestart:
sts i, r17
sts i+1, r18
sts i+2, r19
; ==== BASS ====
; bassptr(r20) = (i >> 13) & 0xF
mov r20, r17
ror r20
mov r20, r18
ror r20
swap r20
andi r20, 0xF
out OCR0AL, r18
; if (i >> 19) & 1: bassptr |= 0x10
sbrc r17, 3
ori r20, 0x10
; note = notes[bassline[bassptr]]
ldi r31, hi8(bassline+0x4000)
ldi r30, lo8(bassline)
add r30, r20
ld r20, Z
ldi r30, lo8(notes)
add r30, r20
ld r21, Z+
ld r20, Z
; if (bassbeat[(i >> 10) & 7]): note <<= 1
mov r22, r18
lsr r22
lsr r22
andi r22, 7
ldi r30, lo8(bassbeat)
add r30, r22
ld r22, Z
tst r22 ; assuming this resets C
breq nobassbeat
rol r21
rol r20
nobassbeat:
; bassosc += note, ret = (bassosc >> 8) & 0x7F
lds r22, bassosc
lds r23, bassosc + 1
add r23, r21
adc r22, r20
sts bassosc, r22
sts bassosc + 1, r23
mov r24, r22
andi r24, 0x7F
; bassflange += note + 1, ret += (bassflange >> 8) & 0x7F
lds r22, bassflange
lds r23, bassflange + 1
inc r21
add r23, r21
adc r22, r20
sts bassflange, r22
sts bassflange + 1, r23
andi r22, 0x7F
add r24, r22
; if ((i >> 6) & 0xF) == 0xF: sample += (bass >> 2)
lsr r24
lsr r24
mov r20, r18
andi r20, 3
subi r20, 3
brne addbass
mov r20, r19
andi r20, 0xC0
subi r20, 0xC0
breq noaddbass
addbass:
add r16, r24
noaddbass:
out OCR0AL, r16
cbi PORTB, 2
rjmp mainloop
.org 0x100
notes:
.word -1, 134, 159, 179, 201, 213, 239, 268, 301, 319, 358, 401, 425, 451, 477, 536, 601, 637, 715
bassline:
.byte 14, 14, 18, 12, 14, 14, 20, 12, 14, 14, 18, 8, 10, 10, 4, 8
.byte 10, 10, 12, 12, 14, 14, 6, 6, 10, 10, 12, 12
bassbeat:
.byte 0, 0, 1, 0, 0, 1, 0, 1