; William Lark, Jr.
;
; How to make something that makes almost anything   Spring 04
; hello_Will.asm
; ref - Neil Gershenfeld CBA MIT 2/14/04
; edited by Will Lark MIT 3/6/04
; AVR 
;

.include "tn15def.inc"
.equ txpin = PB3; transmit pin
.def bitcnt = R16; bit counter
.def temp = R17; temporary storage
.def temp1 = R18; temporary storage
.def txbyte = R19; data byte

.cseg
.org 0
rjmp mainprgm  ; go to the main program "mainprgm"

;
; Program  text output "Hola Buenas tardes"
;
mainprgm:
   sbi PORTB, txpin; init comm pin
   sbi DDRB, txpin
   rptmessage:
      ldi Txbyte, 'H'
      rcall plctext
      ldi Txbyte, 'o'
      rcall plctext
      ldi Txbyte, 'l'
      rcall plctext
      ldi Txbyte, 'a'
      rcall plctext
      ldi Txbyte, ' '
      rcall plctext
      ldi Txbyte, ' '
      rcall plctext
      ldi Txbyte, 'B'
      rcall plctext
      ldi Txbyte, 'u'
      rcall plctext
      ldi Txbyte, 'e'
      rcall plctext
      ldi Txbyte, 'n'
      rcall plctext
      ldi Txbyte, 'a'
      rcall plctext
      ldi Txbyte, 's'
      rcall plctext
      ldi Txbyte, ' '
      rcall plctext
      ldi Txbyte, 't'
      rcall plctext
      ldi Txbyte, 'a'
      rcall plctext
      ldi Txbyte, 'r'
      rcall plctext
      ldi Txbyte, 'd'
      rcall plctext
      ldi Txbyte, 'e'
      rcall plctext
      ldi Txbyte, 's'
      rcall plctext
      ldi Txbyte, ' '
      rcall plctext
      ldi Txbyte, ' '
      rcall plctext
      rcall slowtext
      rjmp rptmessage

;
; Slow down the text "slowtext"
;
.equ delay = 200
slowtext:
   ldi temp1, delay
   rpttext1:
      ldi temp, delay
      rpttext0:
         dec temp
         brne rpttext0
      dec temp1
      brne rpttext1
   ret

;
; Place the Text  "plctext"
;
.equ sb = 1; number of stop bits
plctext:
   ldi bitcnt, 9+sb; 1+8+sb
   com txbyte; invert everything
   sec; set start bit
   plctext0:
      brcc plctext1; if carry set
      sbi PORTB, txpin; send a '0'
      rjmp plctext2; else	
   plctext1:
       cbi PORTB, txpin	; send a '1'
       nop ; even out timing
   plctext2:
       rcall slowbit; one bit delay
       rcall slowbit
       lsr txbyte; get next bit
       dec bitcnt; if not all bits sent
       brne plctext0; send next bit
   ret

;
; Slow down the bit speed  "slowbit"
;
; 1 MHz crystal: 9600 bps - b=14, 19200 bps - b=5, 28800 bps - b=2
;
.equ b = 16
slowbit:
   ldi temp, b
   bitloop:
      dec temp
      brne bitloop
   ret
   
;
; Sow down the text "slowtext"
;
.equ delay = 200
slowtext:
   ldi temp1, delay
   rpttext:
      ldi temp, delay
      rpttext0:
         dec temp
         brne rpttext0
      dec temp1
      brne rpttext1
   ret