Suche Hilfe bei kleinem Projekt: ADC mit ATMEGA8 in Assembler

[MagicWSmoke]

Es sind 4 Messungen, da man dann keine Divisionsroutine benötigt, sondern nur zweimal rechts schieben muss.
Den Rest solltest Du selbst zusammenbringen.

.include "m8def.inc"

.equ    chan    = 0    ; adc-channel

.cseg
.org 0
    rjmp       start
    reti

.org 0x13
start:
    ldi        r16,        high(RAMEND)
    out        SPH,        r16
    ldi        r16,        low(RAMEND)
    out        SPL,        r16
    rcall      adc_init

mainloop:

    rcall      get_adc
    ; do something
rjmp mainloop

get_adc:                                   ; returns averaged result out of 4 samples
    clr        r18                         ; result in r18/r19
    clr        r19
    ldi        r17,        4               ; count of samples
    in         r16,        ADMUX
    andi       r16,        ~(1<<MUX3)|(1<<MUX2)|(1<<MUX1)|(1<<MUX0)
    ori        r16,        chan
    out        ADMUX,      r16
get_sample:
    sbi        ADCSRA,     ADSC            ; start conversion
wait_adc:
    sbic       ADCSRA,     ADSC
    rjmp       wait_adc                    ; wait for conversion ready
    in         r16,        ADCL            ; get result low byte
    add        r18,        r16             ; add
    in         r16,        ADCH            ; get high byte
    adc        r19,        r16             ; add with carry
    dec        r17                         ; decrease sample counter
    brne       get_sample    
    lsr        r19                         ; shift result right = divide by 2
    ror        r18
    lsr        r19                         ; same again, now divided by 4
    ror        r18
ret

adc_init:
    ldi        r16,        (1<<ADEN)|(1<<ADPS2)|(1<<ADPS0)      ; enable adc, adc-prescaler 32
    out        ADCSRA,     r16
    ldi        r16,        (1<<REFS0)                           ; ref is AVCC
    out        ADMUX,      r16
ret