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8. ADC Assembly Code Example

8.1 KodeFull LengkapCode

BerikutHere adalahis contohan kodeexample of AVR Assembly AVRcode untukto membacaread the ADC darifrom the ADC0 pin ADC0using menggunakan referensithe internal 2.56V danreference prescalerand a CLK/128:128 prescaler:

#define __SFR_OFFSET 0x00
#include "avr/io.h"
;------------------------
.global main

main:
    LDI R20, 0xFF
    OUT DDRD, R20       ; Set Port D sebagaias output (ADC result low byte hasil ADC)byte)
    OUT DDRB, R20       ; Set Port B sebagaias output (ADC result high byte hasil ADC)byte)
    SBI DDRC, 0         ; Set pin PC0 sebagaias input untukfor ADC0

    ;-- InisialisasiADC ADCInitialization --
    LDI R20, 0xC0       ; REFS1:REFS0 = 11 → Internal 2.56V
                        ; ADLAR = 0 → Right-justified
                        ; MUX4:MUX0 = 00000 → ADC0
    STS ADMUX, R20

    LDI R20, 0x87       ; ADEN = 1 → Enable ADC
                        ; ADPS2:ADPS0 = 111 → Prescaler CLK/128
    STS ADCSRA, R20

;-- ADC Reading Loop pembacaan ADC --
read_ADC:
    LDI R20, 0xC7       ; Set ADSC = 1 untukto memulaistart konversiconversion
    STS ADCSRA, R20

wait_ADC:
    LDS R21, ADCSRA     ; BacaRead ADCSRA status register ADCSRA
    SBRS R21, 4         ; Skip jump jikaif ADIF (bit 4) = 1 (konversiconversion selesai)complete)
    RJMP wait_ADC       ; LoopWait tungguloop sampaiuntil ADIF is set

    ;-- Reset ADIF flag --
    LDI R17, 0xD7       ; Set ADIF = 1 agarso the controller bisacan reset the flag
    STS ADCSRA, R17

    ;-- BacaRead hasilconversion konversiresult --
    LDS R18, ADCL       ; BacaRead low-byte darifrom ADCL (WAJIBMUST dibacaread dulu)first)
    LDS R19, ADCH       ; BacaRead high-byte darifrom ADCH

    ;-- Output hasilresult --
    OUT PORTD, R18      ; KirimSend low-byte keto Port D
    OUT PORTB, R19      ; KirimSend high-byte keto Port B

    RJMP read_ADC       ; UlangiRepeat pembacaanreading

8.2 PenjelasanCode KodeExplanation

BagianInitialization Inisialisasi:Section:

LDI R20, 0xC0
STS ADMUX, R20
  • 0xC0 dalamin binerbinary = 1100 0000
  • REFS1=1, REFS0=1 → Tegangan referensi internalInternal 2.56V reference voltage
  • ADLAR=0 → Right-justified output
  • MUX4:MUX0 = 00000 → MembacaReading pin ADC0 (A0)
  • BagianThis inipart hanyaruns dijalankanonly sekalionce saatduring inisialisasi.initialization.
LDI R20, 0x87
STS ADCSRA, R20
  • 0x87 dalamin binerbinary = 1000 0111
  • ADEN=1 → ADC diaktifkanis enabled
  • ADPS2:ADPS0 = 111 → Prescaler CLK/128 (125 kHz padaat 16 MHz)

BagianReading PembacaanSection (Loop):

LDI R20, 0xC7
STS ADCSRA, R20
  • 0xC7 dalamin binerbinary = 1100 0111
  • ADEN=1, ADSC=1 → MulaiStart satuone siklusconversion konversicycle
  • ADPS tetapremains samathe same (CLK/128)
wait_ADC:
    LDS R21, ADCSRA
    SBRS R21, 4
    RJMP wait_ADC
  • Polling loop: teruscontinuously membacareads ADCSRA danand mengecekchecks bit 4 (ADIF)
  • SBRS = Skip if Bit in Register Set → jikaif ADIF=1 (konversiconversion selesai)complete), skip RJMP
  • SelamaAs long as ADIF=0 (konversiconversion belumnot selesai)complete), teruscontinue looplooping
LDI R17, 0xD7
STS ADCSRA, R17
  • ResetResets the ADIF flag ADIFby denganwriting cara menulis nilaia 1 keto the ADIF bit ADIF
  • IniThis diperlukanis agarnecessary konversiso berikutnyathe bisanext terdeteksiconversion kembalican be detected
LDS R18, ADCL
LDS R19, ADCH
OUT PORTD, R18
OUT PORTB, R19
  • BacaRead ADCL terlebih dahulufirst (wajib)mandatory), baruthen ADCH
  • KirimSend hasilnyathe keresults to Port D (low-byte) danand Port B (high-byte)
  • KarenaSince it is right-justified: ADCH hanyaonly berisicontains 2 bitbits (bitbits 9 danand 8)
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