;
; hello.RGB.45.asm
;
; RGB LED PWM hello-world
;
; Neil Gershenfeld
; CBA MIT 11/4/07
;
; (c) Massachusetts Institute of Technology 2007
; Permission granted for experimental and personal use;
; license for commercial sale available from MIT.
;

.include "tn45def.inc"
;
; definitions
;
.equ red = PB3; red pin
.equ green = PB4; green pin
.equ blue = PB2; blue pin
.equ rxpin = PB0; receive pin
;
; registers
;
.def temp = R16; temporary storage
.def temp1 = R17; temporary storage
.def count = R17; loop counter
.def pwm = R18; PWM counter

;
; code segment
;
.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
;
; bitdelay
; serial bit delay
;
.equ b = 13 ; 9600 baud (8 MHz clock /8)
bitdelay:
   ldi temp, b
   bitloop:
      dec temp
      brne bitloop
   ret

;
; main program
;
reset:
   ;
   ; set clock divider to /8
   ;
   ldi temp, (1 << CLKPCE)
   ldi temp1, (0 << CLKPS3) | (0 << CLKPS2) | (1 << CLKPS1) | (1 << CLKPS0)
   out CLKPR, temp
   out CLKPR, temp1
   ;
   ; set stack pointer to top of RAM
   ;
   ldi temp, high(RAMEND)
   out SPH, temp
   ldi temp, low(RAMEND)
   out SPL, temp
   ;
   ; init LED pins for output
   ;
   sbi PORTB, red
   sbi DDRB, red
   sbi PORTB, green
   sbi DDRB, green
   sbi PORTB, blue
   sbi DDRB, blue
   ;
   ; main loop
   ;
   main_loop:
      ldi count, 255
      off_red_loop:
         mov pwm, count
         sbi PORTB, red
         off_red_loop_off:
	    dec pwm
	    brne off_red_loop_off
         mov pwm, count
         cbi PORTB, red
	 off_red_loop_on:
	    inc pwm
	    brne off_red_loop_on
         dec count
	 brne off_red_loop
      ldi count, 255
      red_green_loop:
         mov pwm, count
         cbi PORTB, red
         sbi PORTB, green
         red_green_loop_off:
	    dec pwm
	    brne red_green_loop_off
         mov pwm, count
         sbi PORTB, red
         cbi PORTB, green
	 red_green_loop_on:
	    inc pwm
	    brne red_green_loop_on
         dec count
	 brne red_green_loop
      green_blue_loop:
         mov pwm, count
         cbi PORTB, green
         sbi PORTB, blue
         green_blue_loop_off:
	    dec pwm
	    brne green_blue_loop_off
         mov pwm, count
         sbi PORTB, green
         cbi PORTB, blue
	 green_blue_loop_on:
	    inc pwm
	    brne green_blue_loop_on
         dec count
	 brne green_blue_loop
      blue_on_loop:
         mov pwm, count
         sbi PORTB, red
         sbi PORTB, green
         blue_on_loop_off:
	    dec pwm
	    brne blue_on_loop_off
         mov pwm, count
         cbi PORTB, red
         cbi PORTB, green
	 blue_on_loop_on:
	    inc pwm
	    brne blue_on_loop_on
         dec count
	 brne blue_on_loop
      on_off_loop:
         mov pwm, count
         cbi PORTB, red
         cbi PORTB, green
         cbi PORTB, blue
         on_off_loop_off:
	    dec pwm
	    brne on_off_loop_off
         mov pwm, count
         sbi PORTB, red
         sbi PORTB, green
         sbi PORTB, blue
	 on_off_loop_on:
	    inc pwm
	    brne on_off_loop_on
         dec count
	 brne on_off_loop
      rjmp main_loop