viz ok, audio needs work

dither4.s

@@ -25,11 +25,14 @@ temp2 = temp2l
 sample_ptrl = $84
 sample_ptrh = $85
 sample_ptr = sample_ptrl
+scanline = $86
 
 height = 192
 bytes_per_line = 40
 pages_per_frame = 32
 lines_per_frame = 262
+scanline_offset = 31
+scanline_max = (lines_per_frame - scanline_offset) / 2
 
 .data
 
@@ -108,7 +111,7 @@ displaylist:
 
     ; Manually wait for first scan line
 wait_vblank:
-    ;sta WSYNC
+    sta WSYNC
     lda VCOUNT
     bne wait_vblank
 
@@ -116,44 +119,40 @@ wait_vblank:
     lda #$22
     sta DMACTL
 
-; Wait for the next even scanline (VCOUNT is scan line / 2, so look for a change)
 wait_start:
-    lda VCOUNT
-    sta temp1
+    ; Wait for the vblank
+    ; Resynchronize the scanline counter
 wait_loop:
     lda VCOUNT
-    cmp temp1
-    beq wait_loop
+    bne wait_loop
+    lda #(256 - scanline_offset)
+    sta scanline
 
 each_scanline:
-    lda VCOUNT
-    ; Resynchronize the scanline counter
     ; it'll fire on unused lines, but harmlessly
-    clc
-    sbc #15
-    asl
-    tay
 
     .macro audio_prep
         ; audio sample; low nybble
-        ldx #0
-        lda (sample_ptr,x)
-        sta temp2
+        ;ldx #0
+        ;lda (sample_ptr,x)
+        ;sta temp2
 
         ; high nybble
-        lsr a
-        lsr a
-        lsr a
-        lsr a
+        ;lsr a
+        ;lsr a
+        ;lsr a
+        ;lsr a
         ; set the volume-only bit
-        ora #$10
-        pha
+        ;ora #$10
+        ;pha
 
         ; low nybble
-        lda temp2
-        and #$0f
+        ;lda temp2
+        ;and #$0f
         ; set the volume-only bit
-        ora #$10
+        ;ora #$10
+        lda #0
+        pha
         pha
     .endmacro
 
@@ -182,6 +181,8 @@ each_scanline:
     .endmacro
 
     .macro inner_scanline
+        ldy scanline
+
         ; Leisurely memory fetches
         lda palette1,y
         pha
@@ -199,19 +200,22 @@ each_scanline:
         sty COLPF2
         
         ; Audio sample
-        pla
-        sta AUDC1
+        ;pla
+        ;sta AUDC1
     .endmacro
 
-    audio_prep
+    ;audio_prep
     inner_scanline
+    inc scanline
 
-    audio_inc
-    iny
+    ;audio_inc ; too slow?
     inner_scanline
+    inc scanline
 
-    ;jmp wait_start    
-    jmp each_scanline
+    lda VCOUNT
+    cmp #130
+    bne each_scanline
+    jmp wait_start
 
 .endproc