;
; efe.charge.asm
; (c) Neil Gershenfeld CBA MIT 8/29/04
;
; definitions
;
.include "tn13def.inc"
.equ txpin = PB2; transmit pin
.equ ledpin1 = PB3; LED pin 1
.equ ledpin2 = PB4; LEP pin 2
.equ rxpin = PB0; recieve pin

.def bitcnt = R16 ; bit counter
.def temp = R17	; temporary storage
.def temp1 = R18 ; temporary storage
.def txbyte = R19 ; data byte
.def low_up = R20 ; low byte step up
.def high_up = R21 ; high byte step up
.def complow = R22 ; LED lowstate
.def comphigh = R23 ; LED highstate
.def txbytec = R24 ;  state compare byte
.def txbyteb = R25; temporary storge
.def byte = R26; delay count
;.def temp2 = R27;
; start of code
;
.cseg
.org 0
rjmp reset ; jump to reset routine
;
; putchar routine
; assumes no line driver (doesn't invert bits)
;
.equ sb = 1 ;  number of stop bits
putchar:
   ldi bitcnt, 9+sb ; 1+8+sb
   com txbytec ; invert everything
   sec ; set start bit
   putchar0:
      brcc putchar1 ; if carry set
      sbi PORTB, txpin ; send a '0'
      rjmp  putchar2 ; else	
   putchar1:
      cbi PORTB, txpin ; send a '1'
      nop
   putchar2:
      rcall bitdelay ; one bit delay
      rcall  bitdelay
      lsr txbytec ; get next bit
      dec bitcnt ; if not all bits sent
      brne putchar0 ; send next
   ret ; else return

;
; 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 byte ; otherwise shift bit into receive byte
      rjmp getchar2 ; go get next bit
   getchar3:
      ret
;
; serial bit delay routine
;
.equ b = 17 ; OSCCAL 0xff, 5V
bitdelay:
   ldi temp, b
   bitloop: dec temp
   brne bitloop
   ret
;
; routine to wait for sample to settle
;
;.equ delay = 10
;settle:
   ;ldi temp1, delay
  ; sloop1:
     ; ldi temp, delay
     ; sloop0:
      ;   dec temp
      ;   brne sloop0
      ;dec temp1
     ; brne sloop1
   ;ret
;
; print delay
;
.equ delay = 200
print_delay:
   ldi temp1, delay
   delay_loop1:
      ldi temp, delay
      delay_loop:
	     ;ldi temp2, count
         ;delay_loop2:
            ;dec temp2
            ;brne delay_loop2
         dec temp
         brne delay_loop	
      dec temp1
      brne delay_loop1
   ret
;
; main program
;
reset:	   
   ldi temp, low(RAMEND) ; maximum RC clock
   out SPL, temp
   sbi PORTB, txpin; init comm pin
   sbi DDRB, txpin
   sbi PORTB, ledpin1; init LED pin
   sbi DDRB, ledpin1
   sbi PORTB, ledpin2; init LED pin
   sbi DDRB, ledpin2
   ;
   ; init A/D
   ;
   ;cbi ADMUX, REFS1 ; use Vcc as reference
   ;cbi ADMUX, REFS0 ; "
   ;cbi ADMUX, ADLAR ; right-adjust result
   ;sbi ADCSRA, ADEN ; enable A/D
   ;cbi ADCSRA, ADATE ; set for single-shot
   ;cbi ADCSRA, ADIE ; disable A/D interrupt
   ;cbi ADCSRA, ADPS2 ; set prescaler
   ;cbi ADCSRA, ADPS1 ; "
   ;cbi ADCSRA, ADPS0 ; "
   ;sbi PORTB, PB1 ; output on PB1
   ;sbi DDRB, PB1 
   ;cbi ADMUX, MUX2 ; input on ADC1
   ;cbi ADMUX, MUX1 ; "
   ;sbi ADMUX, MUX0 ; "
   ;
   ; infinite main loop
   ;
   loop:
      ;
      ;clr txbyte
	  ;clr txbytec
	  ;clr txbyteb
	  ;
      ; settle sample and start upward step response
      ;
      ;cbi PORTB, PB1
      ;rcall settle
      ;sbi PORTB, PB1
      ;
      ; wait for delay
      ;
      ;nop
      ;
      ; read response
      ;
      ;sbi ADCSRA, ADSC ; start conversion
      ;adloop1up:
         ;sbic ADCSRA, ADSC ; loop until complete
         ;rjmp adloop1up
      ;
      ; save conversion
      ;
      ;in low_up, ADCL ; save low byte
      ;in high_up, ADCH ; save high byte
      ;
      ; start downward step response
      ;
      ;cbi PORTB, PB1
      ;
      ; wait for delay
      ;
      ;nop
      ;
      ; read response
      ;
      ;sbi ADCSRA, ADSC ; start conversion
      ;adloop1down:
         ;sbic ADCSRA, ADSC ; loop until complete
         ;rjmp adloop1down
      ;
      ; send downward conversion
      ;
      ;in txbyte, ADCL ; send low byte
	  ;clr txbyte
      ;rcall putchar
      ;in txbyte,ADCH ; send high byte
	  ;clr txbyte
      ;rcall putchar
      ;
      ; send upward conversion
      ;
      ;mov txbyteb, low_up
      ;rcall putchar
      ;mov txbytec, high_up
      ;rcall putchar
      ;
      ; send 1 2 3 4 for framing
      ;
      ;ldi txbyte, 1
      ;rcall putchar
      ;ldi txbyte, 2
      ;rcall putchar
      ;ldi txbyte, 3
      ;rcall putchar
      ;ldi txbyte, 4
      ;rcall putchar
      ;
      ; print delay
      ;
	  ;ldi comphigh,0
	  ;cp comphigh, txbytec
	  ;breq low_loop
	  ;rcall putchar
      ;rjmp loop

;low_loop:
      rcall getchar
	  ldi txbyte, 4
	  cp byte, txbyte
	  brne loop
	  ;brne left_loop
	  cbi PORTB, ledpin1
      cbi PORTB, ledpin2
	  ldi txbytec, 4
      rcall putchar
      rcall print_delay
      sbi PORTB, ledpin1
      sbi PORTB, ledpin2
      rcall print_delay
      ldi txbytec, 4
      rcall putchar
      rjmp loop

;left_loop:
    ; cbi PORTB, ledpin2
    ; ldi txbytec, 3
    ; rcall putchar
     ;rcall print_delay
     ;sbi PORTB, ledpin2
     ;rcall print_delay
	 ;rjmp loop