**************************************
* File:    R&D11.ASM                 *
* Purpose: Automatic Guitar Tuner    *
* Team:    E-A-D-G-B-E               *
* Designers: Ron Holmes & Dan Gates  *
**************************************


MEM 	EQU	$B6E0		;reserve 1 memory byte for debugging
MEM2	EQU	$B6E1		;reserve 2 memory bytes for storing each sample
MEM3	EQU	$B6E3		;reserve 2 memory bytes for final result
TFLG1   EQU     $1023		;registers for input compare
TMSK1   EQU     $1022
TIC1    EQU     $1010
TCTL2   EQU     $1021
R_EDGE	EQU	$10		;mask for setting input to rising edge
IC1F	EQU	$04		;mask for clearing the input compare flag

*********************************************************************************************
	
        ORG     $B600		;start of program
        LDAA	#%11111111	;mask to set port C direction
        STAA	$1007		;location of DDRC control reister for port C
        LDAA 	#$00
        STAA	$1003		;set tuner motor to off
        
WAIT    LDAA    #R_EDGE		;we are going to wait in this loop until
        STAA    TCTL2		;a string is plucked.
        LDAA    #IC1F
        STAA    TFLG1
        LDAA	#IC1F
        ANDA    TFLG1
        BEQ     WAIT		;when string is plucked jump into a 1.5 second delay
	
*1.5 sec delay
	ldy	#$007C		;set up delay outer loop size
	jsr	delay		;delay for 1 second
	
		
START:  LDD	#$0000		;load register D with zero
        STD	MEM		;clear each memory location
        STD	MEM2		;by sending the 0's in the D reister
        STD	MEM3		;out to the memory locations.	
        
        LDX	#10		;load register X with the number of samples to be taken	
       
SETUP	LDS 	#$01FF		;set the stack pointer to this value
	DES			;decrement the stack to get it set up
	DES			;this creates a false stack
	TSY			;transfer the new stack pointer value to the Y register
	LDAA	#R_EDGE		;load register A with edge trigger mask
	STAA	TCTL2		;send A to the control register for edge triggering
        LDAA    #IC1F		;load register A with clear flag mask
        STAA    TFLG1		;clear the input compare flag
        
TEST	LDAA	#IC1F		;beginning of the first edge capture
	ANDA	TFLG1		;AND register A with the input to see if there is a signal
	BEQ	TEST		;loop back if this was a false start
	LDD	TIC1		;bring the start time, first edge, in to register D 
	STD	0,Y		;store the value to the false stack
	LDAA	#IC1F		;clear the timer flag and get it ready for the second edge
	STAA	TFLG1
	
TEST2	LDAA	#IC1F		;beginning of the second edge capture
	ANDA	TFLG1		;AND register A with the input to see if there is a signal
	BEQ	TEST2		;loop back if second edge hasn't arrived yet
	LDD	TIC1		;bring the end time, second edge, in to register D
	SUBD	0,Y		;subtract the first edge time from the second edge time
	STAA	MEM		;store the result to memory for debugging
	TAB			;transfer those results to register B
	ANDA	#$00		;clear register A
	ADDD	MEM2		;add these results with other sampled results
	STD	MEM2		;store the sum back to memory
	DEX			;decrement the sample counter
	BGT	SETUP		;if count is not at zero then go back and get another sample
	LDD	MEM2		;if count is zero the bring the total sum into Register D
	LDX	#$000A		;load register X with the number of samples
	IDIV			;Divide the sum by the number of samples to get an average
	STX	MEM3		;store the sampled average to memory
	
*Tuned too low?	
	CPX	#$0060		;check to see if the string is tuned
	BHI	TUNE_UP		;if the pitch is too high jump to TUNE_DOWN routine
	
*In tune?
*	CPX	#$0060		;if the pitch is not too high check to see if it's tuned
*	BHS	STOP		;if the string is tuned then STOP the program
	
*Tuned too low?	
	BRA	STOP		;if the string is not too high or in tune then
	NOP			;it must be too low so jump to TUNE_UP routine
	
*********************************************************************************************	

**************************************
* Subroutine to tune the guitar down *
**************************************

TUNE_DOWN: LDAA	#%01000001
	  STAA	$1003
	  BRA	START

**************************************
* Subroutine to tune the guitar up   *
**************************************

TUNE_UP:  LDAA	#%01000001
	  STAA	$1003
	  BRA	START
	  
**************************************
* Subroutine to stop tuning and end  *
**************************************

STOP:	  LDAA	#%00000000
	  STAA	$1003
	  BRA	START
	  
************************************
* delay: delay subroutine          *
* Pass outer loop value in Y       *
************************************
delay:		LDX	#$0FFF		;inner delay loop
delay2:		DEX
		BNE	delay2
		DEY
		BNE	delay
		RTS