;***********************************************;
;	First PIC program			;
;	   					;
;	Implented a Motor Controller		;
;						;
;						;
;						;
;************************************************
    					;Testing and Simulation
	LIST	P=PIC16F877A		;tell assembler what chip we are using
	include "P16F877A.inc"		;include the defaults for the chip
	__config 0x3D18			;sets the configuration settings 
					;(oscillator type etc.)


;****** Variables **************************************************************

	TEMPW	EQU     H'20'   	;This is the start of the General Registers.

	Motor0	EQU	H'21'		; Motor0 speed
	Motor1	EQU	H'22'		; Motor1 speed

	CurMtr0	EQU	H'23'		; Current Motor0 speed
	CurMtr1	EQU	H'24'		; Current Motor1 speed

	count1	EQU	H'25'		; Delay Variables.
	counta	EQU	H'26'
	countb	EQU	H'27'		



	reverse	EQU	H'28'		;Reverse flag


	org	0x0000			;org sets the origin, 0x0000
	goto 	main			;this is where the program starts running	



	org	0x0004			;org sets the origin, 0x0004
	goto	IntH			;this is where interrupts are vectored	



main
   	bsf 	STATUS,		RP0	;set   RP0
	bcf 	STATUS,		RP1	;clear RP1	This selects Bank 1

   	movlw 	b'00000000'		;Set all ports to output
   	movwf 	TRISE
   	movwf 	TRISD
   	movwf 	TRISC
   	movwf 	TRISB
	movwf	TRISA
	bsf	TRISB,		0	; Using RB0/INT as interrupt here.

	bcf	OPTION_REG,	T0CS	; Use interal CS for T0
	bsf	OPTION_REG,	INTEDG	; Interrupt Edge trigger.

	bsf	INTCON, 	GIE	;Global Interrupt Enable   (set)
	bsf	INTCON, 	INTE	;External Interrupt Enabel (set)
	bcf	INTCON, 	INTF	;External Intterupt flag

	movlw	d'20'
	movwf	SPBRG			;Set the baud rate.

   	bcf	TXSTA,		TX9	;8bit transmission
	bsf	TXSTA,		TXEN	;Transmit Enable bit
	bcf	TXSTA,		SYNC	;Asynchro mode   idk?
	bcf	TXSTA,		BRGH	;low speed baud rate

   	bcf 	STATUS,		RP0	;clear RP0
	bcf 	STATUS,		RP1	;clear RP1	This will select bank 0

   	bsf	RCSTA,		SPEN	;Serial Port Enable. Do I need this? sure..
	bcf	RCSTA,		RX9	;8bit receive
	bcf	RCSTA,		CREN	;Continous Receive disable

	movlw 	0x00			;Set the current speed for M0
   	movwf 	CurMtr0	 		;Set the current speed for M1
   	movwf 	CurMtr1			

	movlw 	0x30			;Set the default speed for M0
   	movwf 	Motor0	 		;Set the default speed for M1
   	movwf 	Motor1			

	movlw 	0x00			;Set the reverse flag (defualt: forward)
   	movwf 	reverse		

	movlw	0x00
	movwf	PORTA
	movwf	PORTB
	movwf	PORTC
	movwf	PORTD
	movwf	PORTE


	call 	Delay			; Let motor controller initialize
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay

   	movlw 	b'00000001'		;Set A0 on
   	movwf 	PORTA



Loop	
;	movlw	0xff
;	movwf	PORTA

	movlw 	b'01111111'		;Set the default speed for M0
   	movwf 	Motor0	 		;Set the default speed for M1
   	movwf 	Motor1
	call 	Forward		; Update the motor speeds if needed

	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay


;;	movlw	0x00
;;	movwf	PORTA

	movlw 	b'00000000'		;Set the default speed for M0
   	movwf 	Motor0	 		;Set the default speed for M1
   	movwf 	Motor1
	call 	Forward

	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay
	call 	Delay


	goto	Loop			;go back and do it again




Forward
	movlw 	0x00			;Go forward
 	movwf 	reverse		

	call 	UpdateMotors		; Update the motor speeds if needed
	return
	
;Reverse
;	movlw 	0x01			; Reverse
;   	movwf 	reverse		
;
;	call 	UpdateMotors		; Update the motor speeds if needed
;	return
	


	
UpdateMotors				;Check to see if we want the speed changed. If so, Change it.

updm0
	movfw	CurMtr0			; Current motor speed in W
	xorwf	Motor0,		0	; Xor Current motor speed with wanted motor speed
	btfsc 	STATUS,		Z	;Test if the last operation resulted in 0
	goto	updm1			;Skip to motor1 check if we dont need to update M0
	call	SerStart
	movlw	b'0000001'
	subwf   reverse,0
	movwf	TXREG
	call	SerChk
	movfw	Motor0
	movwf	TXREG
	movwf	CurMtr0

updm1
	movfw	CurMtr1			; Current motor speed in W
	xorwf	Motor1,		0	; Xor Current motor speed with wanted motor speed
	btfsc 	STATUS,		Z	;Test if the last operation resulted in 0
	return				;Return if we dont need to update M1
	call	SerStart
	movlw	b'0000011'
	subwf   reverse,0
	movwf	TXREG
	call	SerChk
	movfw	Motor1
	movwf	TXREG
	movwf	CurMtr1
	return


SerStart
	call 	SerChk
	movlw	0x80
	movwf	TXREG
	call	SerChk
	movlw	0x00
	movwf	TXREG	
	call	SerChk
	return

SerChk
	btfss 	PIR1,		TXIF	;Test if the data has been sent to buffer
	goto	$-1			;Does this work?
	return



Delay
	movlw	d'250'			;delay 250 ms (4 MHz clock)
	movwf	count1
d1	movlw	0xC7
	movwf	counta
	movlw	0x01
	movwf	countb
Delay_0
	decfsz	counta, f
	goto	$+2
	decfsz	countb, f
	goto	Delay_0

	decfsz	count1	,f
	goto	d1
	return



;----Our Interrupt Handler will go here.----;

IntH
	movwf	TEMPW

	nop	
	nop
	nop
	nop

	bcf	INTCON,		INTF	;Lets set thing back..
	movfw	TEMPW              	;Restore w
	RETFIE
	




	end