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+Following code snippets should give you an inspiration, how an existing assembly based applications like [[MIDIbox64]] or [[MIDIbox64E]] can be easily enhanced by additional button functions, which send statically assigned MIDI events.
+The idea is to overlay the USER_DIN_NotifyToggle hook. This hook is called by MIOS when a digital input has changed its state (0V->5V or 5V->0V). You can check if a DIN number is within the button range, which should be overlayed. If it is outside the range, then just continue with the application specific code, which handles the remaining buttons - thats all.
+Technical details:
+The hook is normaly located in the main.asm file of the application.
+MIOS forwards following parameters to the hook:
+MIOS_PARAMETER1: contains the number of the digital input, counted from zero (0..127)
+MIOS_PARAMETER2: bit #0 is 0, when the digital input is at 0V, and 1, if the digital input is at 5V
+If buttons are connected, this means: 0V when button closed (pressed), 5V when button open (depressed)
+The button range can be checked with the IFLEQ (if-less-equal) and IFGEQ (if-greater-equal) macros, which are defined in macros.h:
+<code asm>
+	;; overlay DIN input #64-#127 (counted from zero) by a simple
+	;; function which sends dedicated Note Events
+	movlw	64-1
+	IFLEQ	MIOS_PARAMETER1, ACCESS, rgoto USER_DIN_NotifyToggle_NoOverlay
+	movlw   127+1
+	IFGEQ	MIOS_PARAMETER1, ACCESS, rgoto USER_DIN_NotifyToggle_NoOverlay
+USER_DIN_NotifyToggle_Overlay
+	movlw	0x90			; Note Event, MIDI Channel #1
+	call	MIOS_MIDI_TxBufferPut
+	movf	TMP1, W			; DIN number -> Note Number
+	call	MIOS_MIDI_TxBufferPut
+	movlw	0x7f			; Velocity: 0x7f if button pressed
+	IFSET	MIOS_PARAMETER2, 0, movlw 0x00	;   0x00 if button depressed
+	call	MIOS_MIDI_TxBufferPut
+	return				; exit
+USER_DIN_NotifyToggle_NoOverlay
+	;; ...rest of the application specific code
+</code>
+An interesting variation is following example, which sends different MIDI events depending on a certain button - we could call it "SHIFT" button:
+<code asm>
+	;; overlay DIN input #64-#127 (counted from zero) by a simple
+	;; function which sends dedicated Note Events
+	movlw	64-1
+	IFLEQ	MIOS_PARAMETER1, ACCESS, rgoto USER_DIN_NotifyToggle_NoOverlay
+	movlw   127+1
+	IFGEQ	MIOS_PARAMETER1, ACCESS, rgoto USER_DIN_NotifyToggle_NoOverlay
+USER_DIN_NotifyToggle_Overlay
+;; since MIOS_DIN_PinGet overwrites MIOS_PARAMETER1, store current button number in TMP1
+	movff	MIOS_PARAMETER1, TMP1
+	;; we are using button #8 as shift button (it's outside the range which is overlayed)
+	movlw	8		; get value of this button (0=pressed, 1=depressed)
+	call	MIOS_DIN_PinGet
+	bz	USER_DIN_NotifyToggle_Overlay_1	; branch depending on selection state --- bz == "branch if zero"
+USER_DIN_NotifyToggle_Overlay_0
+	movlw	0x90			; Note Event, MIDI Channel #1
+	call	MIOS_MIDI_TxBufferPut
+	movf	TMP1, W			; DIN number -> Note Number
+	call	MIOS_MIDI_TxBufferPut
+	movlw	0x7f			; Velocity: 0x7f if button pressed
+	IFSET	MIOS_PARAMETER2, 0, movlw 0x00	;   0x00 if button depressed
+	call	MIOS_MIDI_TxBufferPut
+	return				; exit
+USER_DIN_NotifyToggle_Overlay_1
+	movlw	0x91			; Note Event, MIDI Channel #2
+	call	MIOS_MIDI_TxBufferPut
+	movf	TMP1, W			; DIN number -> Note Number
+	call	MIOS_MIDI_TxBufferPut
+	movlw	0x7f			; Velocity: 0x7f if button pressed
+	IFSET	MIOS_PARAMETER2, 0, movlw 0x00	;   0x00 if button depressed
+	call	MIOS_MIDI_TxBufferPut
+	return				; exit
+USER_DIN_NotifyToggle_NoOverlay
+	;; ...rest of the application specific code
+</code>
+Please note: if you have ideas for much more complex button functions, but no motivation to learn assembly language, just consider the use of the SDCC wrapper - see also the examples at [[http://www.ucapps.de/mios_c.html|this Page]]
+Unfortunately it is not possible to combine the assembly based applications like [[MIDIbox64]] or [[MIDIbox64E]] with C programs, but maybe your requirements to the application don't match with these historic MIDIboxes anyhow (e.g. you don't need on-screen editing capabilities, you don't need several banks of buttons/encoders/pots/fader setups, you only want to send unique MIDI events to a host ), that it makes sense to program a small C based application instead, and especially to share it with other MIDIbox users!
+Additional Hints: \\
+  * please note, that digital inputs could already be overlayed by the encoder handler. The encoder pins are pre-defined in mios_tables.inc (if you are compiling a main.asm file, in some applications the table could also be located in a setup_*.asm file) \\ So, if some of the DINs don't send a MIDI event, it makes sense to check the encoder table!
+  * you could also overlay *all* button functions this way if you want, just remove the button range checks - pins which are assigned to rotary encoders are not affected (they don't trigger the MIOS_DIN_NotifyToggle hook)