beginners/light_control.asm

   1 ;
   2 ; control the light connected to the pwm output pins
   3 ;
   4 ; author: hackbard@hackdaworld.org
   5 ;
   6
   7 ; specify device
   8 .include "../include/2313def.inc"
   9
  10 ; ------------------
  11 ; interrupt vectors:
  12 ; ------------------
  13
  14 ; reset
  15 rjmp RESET
  16 ; int0
  17 reti
  18 ; int1
  19 reti
  20 ; timer 1 capture
  21 reti
  22 ; timer 1 compare
  23 reti
  24 ; timer 1 overflow
  25 reti
  26 ; timer 0 overflow
  27 reti
  28 ; usart rx complete
  29 rjmp UART_RX
  30 ; usart data register empty
  31 reti
  32 ; usart tx complete
  33 reti
  34 ; analog comperator
  35 reti
  36 ; pin change interrupt
  37 reti
  38 ; timer/counter 1 compare match b
  39 reti
  40 ; timer/counter 0 compare match a
  41 reti
  42 ; timer/counter 0 compare match b
  43 reti
  44 ; usi start condition
  45 reti
  46 ; usi overflow
  47 reti
  48 ; eeprom ready
  49 reti
  50 ; watchdog timer overflow
  51 reti
  52
  53 ; -----
  54 ; code:
  55 ; -----
  56
  57 RESET:
  58         ; set stackpointer
  59         ldi r16,low(RAMEND)     ; write top of ramend (lowbyte)
  60         out SPL,r16             ; to stackpointer
  61
  62         ; rs232 init
  63         ldi r16,12      ; "38.4k bps @ 8 mhz" in r16
  64         out UBRR,r16    ; write to uart baudrate register
  65         ldi r16,(1<<RXEN)|(1<<TXEN)|(1<<RXCIE)  ; enable rx/tx + rx interrupt
  66         out UCSRB,r16   ; write to uart control register
  67
  68         ; pwm (OC0A=PB2 OC0B=PD5)
  69         ; set as output
  70         ldi r16,(1<<DDB2)
  71         out DDRB,r16
  72         ldi r16,(1<<DDD5)
  73         out DDRD,r16
  74         ; output 0
  75         ldi r16,(1<<PINB2)
  76         subi r16,0xff
  77         out PORTB,r16
  78         ldi r16,(1<<PIND5)|(1<<PIND6)
  79         subi r16,0xff
  80         out PORTD,r16
  81         ; toggle OC0A/B on compare match / fast pwm
  82         ldi r16,(1<<COM0A0)|(1<<COM0B0)|(1<<WGM00)|(1<<WGM01)
  83         out TCCR0A,r16
  84         ; top in OCR0A / no clock prescaling
  85         ldi r16,(1<<WGM02)|(1<<CS00)
  86         ; overflow interrupt enable
  87
  88         ; initial pwm value 0x7f
  89         ldi r16,0x7f
  90         out OCR0A,r16
  91         out OCR0B,r16
  92
  93         ; global interrupt enable
  94         sei
  95
  96 MAIN:
  97         rjmp MAIN
  98
  99 UART_RX:
 100         reti