;
; i0.6.thtp.asm
;
; Neil Gershenfeld  CBA  MIT  11/27/05
; (c) Massachusetts Institute of Technology 2005
; Permission granted for experimental and personal use;
; license for commercial use available from MIT
;
; transmit a SLIP UDP HTTP (THTP) packet when the button is pushed
; blink the LED when the button is pushed or a click is received
;

.include "tn13def.inc"

.equ ledpin1 = PB1; LED pin
.equ buttonbit = 2; pushbutton bit
.equ buttonpin = PB2; pushbutton pin
.equ clickpin = PB3; click input pin
.equ ledpin2 = PB4; mosfet output pin

.def bitcnt = R16; bit counter
.def txbyte = R17; bit counter
.def temp = R18; temporary storage
.def temp1 = R19; temporary storage
.def count = R20; loop counter
.def check_lo = R21; lo checksum accumulator
.def check_hi = R22; hi checksum accumulator
.def check_carry = R23; checksum carry accumulator
.def zero = R24; 0
.def temp1 = R25;

.equ END = 192
.equ ESC = 219
.equ ESC_END = 220
.equ ESC_ESC = 221

.macro putslip
   ;
   ; putslip
   ; outputs char in txbyte, with SLIP mapping
   ;
   ldi temp, END
   cpse txbyte, temp
   rjmp putslipchar
      mov temp, txbyte
      ldi txbyte, ESC
      rcall putclick
      rcall chardelay
      ldi txbyte, ESC_END
      rcall putclick
      rcall chardelay
      mov txbyte, temp
      rjmp endputslip
   ldi temp, ESC
   cpse txbyte, temp
   rjmp putslipchar
      mov temp, txbyte
      ldi txbyte, ESC
      rcall putclick
      rcall chardelay
      ldi txbyte, ESC_ESC
      rcall putclick
      rcall chardelay
      mov txbyte, temp
      rjmp endputslip
   putslipchar:
      rcall putclick
      rcall chardelay
   endputslip:
      .endmacro

.cseg
.org 0
rjmp reset

 
; putclick
; send char in txbyte clicks
;
putclick:
   ldi bitcnt, 8
   sec; set start bit
   ;
   ; send start clicks
   ;
   sbi PORTB, ledpin2
   ;sbi PORTB, ledpin2
   rcall clickon
   cbi PORTB, ledpin2
   rcall clickdelay
   sbi PORTB, ledpin2
   rcall clickon
   cbi PORTB, ledpin2
   ;cbi PORTB, ledpin2
   rcall clickdelay
   ;
   ; send data clicks
   ;
   putclick0:
      lsr txbyte; get next bit
      brcc putclick1; if carry set, send a 1 click
      sbi PORTB, ledpin2    
      rcall clickon
      cbi PORTB, ledpin2
	  rcall clickdelay
      cbi PORTB, ledpin2
      rcall clickon
	  cbi PORTB, ledpin2
      rcall clickdelay
      rjmp putclick2; otherwise ...
   putclick1:; ... send a 0 click
      cbi PORTB, ledpin2
      rcall clickon
      cbi PORTB, ledpin2
	  rcall clickdelay
      sbi PORTB, ledpin2
      rcall clickon
      cbi PORTB, ledpin2
      rcall clickdelay
   putclick2:
      dec bitcnt; if not all bits sent
      brne putclick0; send next bit
   ;
   ; send stop clicks
   ;
  ;; sbi PORTB, ledpin2
  ;; rcall clickon
  ;; cbi PORTB, ledpin2
   ;;rcall clickdelay
   ;;sbi PORTB, ledpin2
   ;;rcall clickon
  ;; cbi PORTB, ledpin2
  ;; rcall clickdelay
   ret;
;
; clickdelay
; delay between clicks
;
clickdelay:
   ldi temp, 30
   clickdelayloop:
      dec temp
      brne clickdelayloop
   ret

; clickdelay
; delay between clicks
;
clickon:
   ldi temp, 1
   clickonloop:
      dec temp
      brne clickdelayloop
   ret
;
; chardelay
; delay between characters
;
chardelay:
   ldi temp, 200
   chardelayloop:
      ldi temp1, 200
      chardelayloop1:
         dec temp1
         brne chardelayloop1
      dec temp
      brne chardelayloop
   ret
;
; main program
;
reset:
   ldi temp, low(RAMEND) ; set stack pointer to top of RAM
   out SPL, temp ;
   clr zero
   sbi PORTB, buttonpin ; init pushbutton pin for input with pull-up
   cbi DDRB, buttonpin ;
   cbi PORTB, ledpin2 ; init mosfet control pin for output
   sbi DDRB, ledpin2 ; 
   cbi ACSR, ACIS1 ; setup comparator to output on state change
   cbi ACSR, ACIS0 ;
   sbi ADCSRB, ACME ; setup comparator to use ADC multiplexer
   cbi ADCSRA, ADEN ;
   sbi ADMUX, MUX1 ; set channel to ADC3
   sbi ADMUX, MUX0 ;

   loop:
      ;
      ; wait for the button to be pressed or a click to arrive
      ;
      sbi ACSR, ACI ; reset comparator
      waitloop:
         sbic PINB, buttonbit ; check for button
            rjmp waitloop
            ldi txbyte, 4
		    rcall putclick
		    rcall chardelay
		    rcall chardelay
		    rcall chardelay
		    rcall chardelay
		    rcall chardelay
            rjmp loop