atari800: music preset; removed twitter link

index.html

@@ -132,7 +132,7 @@ if (window.location.host.endsWith('8bitworkshop.com')) {
         <a tabindex="-1" href="#">About</a>
         <ul class="dropdown-menu">
           <li><a class="dropdown-item" target="_8bws_help" href="https://8bitworkshop.com/">Website</a></li>
-          <li><a class="dropdown-item" target="_8bws_help" href="https://twitter.com/8bitworkshop">Twitter</a></li>
+          <li><a class="dropdown-item" target="_8bws_help" href="https://oldbytes.space/@8bitworkshop">Mastodon</a></li>
           <li><a class="dropdown-item" target="_8bws_help" href="https://8bitworkshop.com/docs/blog.html">Latest News</a></li>
           <li><a class="dropdown-item" target="_8bws_help" href="https://github.com/sehugg/8bitworkshop/issues/new">Report an Issue</a></li>
         </ul>

presets/atari8-800/pokeymusic.ca65

@@ -0,0 +1,164 @@
+
+AUDF0 =	$d200
+AUDC0 = $d201
+AUDCTL = $d208
+
+.data
+
+Chan0dur:	.res 4	; current note duration channel 0
+Chan0note:	.res 4	; current note pitch channel 0
+Chan0duty:	.res 4	; current duty bits channel 0
+DurationTimer:	.res 1	; duration until next cmd
+CurChannel:	.res 1	; next channel to add note
+Volume:		.res 1  ; initial volume of note (0-31)
+
+; set_irq() saves/restores entire zeropage segment
+; which we don't want!
+; so we have to set this with an equate
+SongPtr = $fe
+;.segment "EXTZP"
+;SongPtr:	.res 2	; ptr to next song byte
+
+.code
+
+; Update channel pitch in AUDF0
+; 8-bit rotation of duty cycle bits
+.export _music_duty
+_music_duty:
+	ldx	#3
+        ldy	#0
+@loop:
+	lda	Chan0dur,x
+        beq	:++
+	lda	Chan0duty,x
+        asl
+        bcc	:+
+        ora	#1
+:	sta	Chan0duty,x
+	lda	Chan0note,x
+        beq	:+
+; If next bit is set, add 1 to AUDF0 
+        adc	#0
+        sta	AUDF0,y
+:
+        iny
+        iny
+	dex
+        bpl	@loop
+	rts
+
+; Decrement the volumes for each channel
+.export _music_tick
+_music_tick:
+	ldx	#3
+        ldy	#0
+@loop1:
+	lda	Chan0dur,x
+        beq	:+
+        lsr
+        ora	#$a0
+        sta	AUDC0,y
+        dec	Chan0dur,x
+:
+	iny
+        iny
+	dex
+        bpl	@loop1
+        
+; Also decrement next-note timer, fetch next note
+        lda	DurationTimer
+        bmi	@Done
+        beq	@NextData
+        dec	DurationTimer
+        rts
+
+; Timer ran out, so fetch next note
+@NextData:
+	ldx	#0
+        lda	(SongPtr,x)
+        bmi	@LoadDuration
+; < $80, play next note
+        ldx	CurChannel	; next channel
+        tay
+        jsr	music_do_note
+        inx
+        txa
+        and	#3
+        sta	CurChannel	; inc next channel
+        jsr	@IncDataPtr
+        jmp	@NextData
+; >= $80, load next duration
+@LoadDuration:
+	cmp	#$ff		; $ff = end of song
+        bne	@NoResetTrack
+        sta     DurationTimer
+        jmp	music_done
+@NoResetTrack:
+        and	#$7f
+;        asl
+        sta	DurationTimer	; store duration * 2
+@IncDataPtr:
+; increment song pointer
+	inc	SongPtr
+        bne	@Done
+	inc	SongPtr+1
+@Done:
+	rts
+
+music_do_note:
+; Play a note
+; X = channel (0,1)
+; Y = note index (0-63)
+	lda	FREQZ,y
+        sta	Chan0note,x
+	lda	DUTYZ,y
+        sta	Chan0duty,x
+        lda	Volume
+        sta	Chan0dur,x
+        rts
+
+music_done:
+	rts
+
+.export _music_start
+_music_start:
+	sta SongPtr
+        stx SongPtr+1
+        lda #24
+        sta Volume
+        lda #0
+        sta DurationTimer
+        sta CurChannel
+        ldx #3
+:       sta Chan0dur,x
+        dex
+        bpl :-
+	lda #$01
+        sta AUDCTL
+        rts
+
+.export _music_get_ptr
+_music_get_ptr:
+	lda SongPtr
+        ldx SongPtr+1
+	rts
+
+.export _music_is_done
+_music_is_done:
+	ldx #0
+        lda (SongPtr,x)
+        cmp #$ff
+        php
+        pla
+        lsr
+        and #1
+	rts
+
+; Table of AUDF base values for each note
+FREQZ:
+  .byte 254, 254, 254, 255, 240, 227, 214, 202, 190, 180, 169, 160, 151, 142, 134, 127, 119, 113, 106, 100, 94, 89, 84, 79, 75, 70, 66, 63, 59, 56, 52, 49, 47, 44, 41, 39, 37, 34, 32, 31, 29, 27, 25, 24, 23, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 11, 10, 9, 9, 8, 8, 7, 7
+
+; Table of duty-cycle bits for each note
+DUTYZ:
+  .byte 0, 0, 0, 0, 181, 1, 17, 1, 219, 0, 239, 17, 17, 181, 181, 0, 239, 0, 181, 181, 239, 85, 73, 181, 1, 239, 219, 0, 73, 0, 239, 219, 0, 17, 219, 73, 0, 239, 239, 0, 17, 85, 239, 73, 0, 181, 73, 1, 0, 0, 0, 0, 1, 17, 85, 219, 0, 73, 181, 1, 85, 0, 85, 0
+  

src/platform/atari8.ts

@@ -15,6 +15,7 @@ var Atari8_PRESETS = [
 ];
 
 var Atari800_PRESETS = Atari8_PRESETS.concat([
+  {id:'testmusic.c', name:'POKEY Music (C)'},
   {id:'sieve.bas', name:'Benchmark (FastBasic)'},
   {id:'pmtest.bas', name:'Sprites Test (FastBasic)'},
   {id:'dli.bas', name:'DLI Test (FastBasic)'},