;
; program for main controller of linear stepper
;
; 
; definitions
;
.include "tn13def.inc"
.def temp = R16	; temporary storage
.def temp1 = R17 ; temporary storage
.def temp2 = R18 ; temporary storage
.def bitcnt = R19 ; for serial
.def rxbyte = R20 ; the byte received by getchar
.def godelay = R21
.def pwmval = R22
.def state = R23

.equ rxpin = PB3 

.equ b1dir = PB2
.equ b2dir = PB4
.equ b1pwm = PB1
.equ b2pwm = PB0

.equ initial_pwmval = 120
.equ initial_delay = 7

.equ forward = 1
.equ back = 2
.equ setpwm = 3
.equ setdelay = 4
.equ gotostate = 5

;bridge 1:
;pwm = PB1, OC0B
;direction = PB2

;bridge 2:
;pwm = PB0, OC0A
;direction = PB4

.cseg
.org 0
rjmp reset


;
; getChar
; assumes no line driver (doesn't invert bits)
;
getChar:
   ldi bitcnt,9 ; 8 data bit + 1 stop bit
   getchar1:
      sbis PINB, rxpin ; wait for start bit
      rjmp getchar1
   rcall bitdelay ; 0.5 bit delay
   getchar2:
      rcall bitdelay ; 1 bit delay
      rcall bitdelay ;
      clc ; clear carry
      sbis PINB, rxpin ; if RX pin high skip
         sec ; otherwise set carry
      dec bitcnt
      breq getchar3 ; return if all bits read
      ror rxbyte ; otherwise shift bit into receive byte
      rjmp getchar2 ; go get next bit
   getchar3:
      ret
;
; bit delay
;.equ b = 35 ; OSCCAL = 0xff 9600 bps 3.3V
;.equ b = 38  ;for 38400
.equ b = 160 ;for 9600
bitdelay:
   ldi temp, b
   bitloop:
      dec temp
      brne bitloop
   ret


driveTimer:
	mov temp2, godelay
	DelayOuterOuter:
		ldi temp1, 250
		DelayOuter:
			ldi temp, 250
			DelayInner:
				dec temp
				brne DelayInner
			dec temp1
			brne DelayOuter
		dec temp2
		brne DelayOuterOuter
	ret


DoState:
	cpi state, 0
	breq State0
	cpi state, 1
	breq State1
	cpi state, 2
	breq State2
	cpi state, 3
	breq State3
	ret
State0:
	sbi PORTB, b1dir
	out OCR0B, pwmval
	rjmp FinishState
State1:
	sbi PORTB, b2dir
	out OCR0A, pwmval
	rjmp FinishState
State2:
	cbi PORTB, b1dir
	out OCR0B, pwmval
	rjmp FinishState
State3:
	cbi PORTB, b2dir
	out OCR0A, pwmval
	rjmp FinishState
FinishState:
	rcall driveTimer
	ldi temp, 0
	out OCR0B, temp
	out OCR0A, temp
	ret

;
; main program
;
reset:	   
	;
	; initialization
	;
	ldi temp, low(RAMEND)
	out SPL, temp ; set stack pointer to top of RAM
	ldi temp, (1<<CLKPCE)
	ldi temp1, ((0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0))
	out CLKPR, temp ; write CLKPCE to change clock prescaler
	out CLKPR, temp1 ; set clock to 9.6MHz/1
	
	
	;
	; init PWM
	;
	;ldi temp, ((1 << COM0B0) | (1 << COM0B1) | (1 << WGM01) | (1 << WGM00))
	
	;fast pwm (WGM02:0 = 3), non inverted operation for b, (COM0B1:0 = 2), and a (COM0A1:0=2)
	ldi temp, ((0 << COM0B0) | (1 << COM0B1) | (0 << COM0A0) | (1 << COM0A1) | (1 << WGM01) | (1 << WGM00))  
	out TCCR0A, temp; 
	
	;ldi temp, (1 << CS00) ; timer prescaler 1
	ldi temp, (1 << CS01) ; 8
	;ldi temp, (1 << CS02) | (1 << CS00) ; 1024
	out TCCR0B, temp 
	
	ldi temp, 0 ; zero is low all the time, 255 high all the time.
	sbi DDRB, b1pwm ; enable OC0B output pin
	out OCR0B, temp ; set pwm to off
	sbi DDRB, b2pwm ; enable OC0A output pin
	out OCR0A, temp ; set pwm to off
	
	sbi DDRB, b1dir ; enable direction pin
	sbi PORTB, b1dir
	sbi DDRB, b2dir ; enable direction pin
	cbi PORTB, b2dir
	
	ldi godelay, initial_delay
	ldi pwmval, initial_pwmval
	ldi state, 0
	
;		sbi DDRB, b1pwm ; disable output
;		sbi DDRB, b2pwm ; disable output
;		sbi DDRB, b1dir ; disable output
;		sbi DDRB, b2dir ; disable output
	
	LOOP:
	
		ldi state, 0
		rcall DoState
		nop
		
		ldi state, 1
		rcall DoState
		nop
		
		ldi state, 2
		rcall DoState
		nop

		ldi state, 3
		rcall DoState
		nop

	
		ldi state, 0
		rcall DoState
		nop

		ldi state, 1
		rcall DoState
		nop
		
		ldi state, 2
		rcall DoState
		nop

		ldi state, 3
		rcall DoState
		nop

		
		ldi state, 3
		rcall DoState
		nop

		ldi state, 2
		rcall DoState
		nop
		
		ldi state, 1
		rcall DoState
		nop

		ldi state, 0
		rcall DoState
		nop
		
		ldi state, 3
		rcall DoState
		nop

		ldi state, 2
		rcall DoState
		nop
		
		ldi state, 1
		rcall DoState
		nop

		ldi state, 0
		rcall DoState
		rcall bitdelay
		rjmp LOOP
		
		
		
		
		
		
		inc state
		cpi state, 4
		brlo OKL
			ldi state, 0
		OKL:
		rcall DoState
		rcall driveTimer
		rjmp LOOP


		rcall getChar
		rcall bitdelay
		rcall bitdelay
		;mov state, rxbyte
		ldi state, 0
		rcall DoState
		rjmp LOOP
		cpi rxbyte, forward
		breq GoForwardLabel
		cpi rxbyte, back
		breq GoBackLabel
		cpi rxbyte, gotostate
		breq GotoStateLabel
		rjmp LOOP
		cpi rxbyte, setpwm
		breq SetPWMLabel
		cpi rxbyte, setdelay
		breq SetDelayLabel
		
		rjmp LOOP
		
	GoForwardLabel:
		inc state
		cpi state, 4
		brlo OKF
			ldi state, 0
		OKF:
		rcall DoState
		rjmp LOOP
	GoBackLabel:
		cpi state, 0
		brne OKB
			ldi state, 4
		OKB:
		dec state
		rcall DoState
		rjmp LOOP
	SetPWMLabel:
		;rcall getChar
		;mov pwmval, rxbyte
		;ldi pwmval, 50
		inc pwmval
		rjmp LOOP
	SetDelayLabel:
		rcall getChar
		rcall bitdelay
		rcall bitdelay
		mov godelay, rxbyte
		rjmp LOOP
	GotoStateLabel:
		rcall getChar
		rcall bitdelay
		rcall bitdelay
		mov state, rxbyte
		rcall DoState
		rjmp Loop