Hey All, me again!
So, in my last post I was trying to achieve a fade effect manually, but i found that simply changing bits 5 and 6 on the value written to $4000 would do that just fine for my needs AND I can modify the length using the highest 5 bits written to register $4003. Awesome.
Now my issue seems to be an inability to trigger a sequence of more than one note.
I know that once the counter reaches 0 on the note length, the flag for the note length at register $4015 will set to 0.
My code looks like this:
.inesprg 1
.ineschr 0
.inesmap 1
.inesmir 0
.bank 1
.org $FFFA
.dw 0 ;vbank
.dw Main
.dw 0
.bank 0
.org $C000
Main:
;period/frequ and also set length
One:
JSR D3
ldx $4015
cpx #%00000000
beq Two
Infiniteloop
jmp Infiniteloop
Two:
JSR D4
jmp Infiniteloop
D3:
;D3, eighth note
lda #%00000001
sta $4015
lda #%10011111
sta $4000
lda #%11111001
sta $4002
lda #%01001010
sta $4003
RTS
D4:
lda #%00000001
sta $4015
lda #%10011111
sta $4000
lda #%01111100
sta $4002
lda #%01001001
sta $4003
RTS
In my head, the code should.
1. From main, jump to my subroutine D3, where I
a. enable PU1 by writing 1 to the first bit of register $4015
b. write the duty cycle/volume/period/length data to registers $4000, $4002, and $4003
c. return to main
2. Load the value stored at $4015 to the x register
3. test the value against a correct zero-d out $4015, meaning that the timer on PU1 had counted to zero
4. Jump to D4, where i would do the same process as in step one.
On paper, i feel like my code checks out, but clearly i am missing something here, so if anyone could help me (again) that would be extremely cool.
Thanks!