chiptune: have arrow keys and pause working

chiptune_player/chiptune_player.s

@@ -200,26 +200,31 @@ check_done:
 	bit	DONE_PLAYING
 	beq	main_loop	; if was all zeros, loop
 	bmi	main_loop	; if high bit set, paused
+	bvs	minus_song	; if bit 6 set, then left pressed
 
+				; else, either song finished or
+				; right pressed
+
+plus_song:
+	sei			; disable interrupts
+	jsr	increment_file
+	jmp	done_play
+
+minus_song:
+	sei			; disable interrupts
+	jsr	decrement_file
 
 done_play:
 
-;				; FIXME: disable timer on 6522
-;				; FIXME: unhook interrupt handler
-;
-	sei			; disable interrupts
-
 	lda	#0
 	sta	DONE_PLAYING
 
-	jsr	clear_ay_both
-
 	lda	#0
 	sta	CH
 
 	jsr	clear_bottoms
 
-	jsr	increment_file
+
 	jsr	new_song
 
 	cli				; re-enable interrupts

chiptune_player/interrupt_handler.s

@@ -92,7 +92,6 @@ mb_write_loop:
 	bne	mb_not_done						; 3/2nt
 
 	lda	#1		; set done playing			; 2
-	sta	DONE_PLAYING						; 3
 
 	jmp	quiet_exit						; 3
 
@@ -283,25 +282,30 @@ check_keyboard:
 key_space:
 	lda	#$80
 	eor	DONE_PLAYING
-	sta	DONE_PLAYING
-
-	bne	quiet_exit
+	jmp	quiet_exit
 
 key_left:
-	cmp	#'D'
+	cmp	#'A'
 	bne	key_right
 
+	lda	#$40
+	bne	quiet_exit
+
 key_right:
-	cmp	#'A'
+	cmp	#'D'
 	bne	done_key
 
+	lda	#$20
+	bne	quiet_exit
+
 done_key:
 	jmp	exit_interrupt
 
 quiet_exit:
+	sta	DONE_PLAYING
 	jsr	clear_ay_both
-exit_interrupt:
 
+exit_interrupt:
 
 	pla			; restore a				; 4