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;;

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;; Basic ADC operation

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;;

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; Reference select

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.set ADC_REF    = 0b01      ; AVcc

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; Bit adjustment

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.set ADC_LAR    = 1         ; Left-adjust

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; Input select

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.set ADC_MUX    = 0b000     ; ADC0

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; Auto-trigger source

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.set ADC_ATS    = 0b011     ; TC0 OCA

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; Auto-trigger enable

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.set ADC_ATE    = 1

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; Prescaler

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.set ADC_PS     = 0b111     ; 1/128

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; I/O pins

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.equ ADC_DDR    = DDRC

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.equ ADC_PORT   = PORTC

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.equ ADC_PIN    = PORTC0

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;; Initialize the ADC for starting conversions

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ADC_Init:

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    ; ADMUX

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        ldi         r16, (ADC_REF << REFS0) | (ADC_LAR << ADLAR) | (ADC_MUX << MUX0)

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        sts         ADMUX, r16

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    ; ADCSRB

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        ldi         r16, (ADC_ATS << ADTS0)

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        sts         ADCSRB, r16

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    ; ADCSRA

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        ; ADSC: No need if using external auto-trigger ???

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        ; Enable interrupt

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        ldi         r16, (1 << ADEN) | (1 << ADSC) | (ADC_ATE << ADATE) | (1 << ADIE) | (ADC_PS << ADPS0)

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        sts         ADCSRA, r16

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    ; Disable digital circuit for pin

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        ldi         r16, (1 << ADC_PIN)

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        sts         DIDR0, r16

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    ; Done

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        ret

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;; Interrupt handler stub for ADC_HANDLER

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ADC_Interrupt:

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        in          r0, SREG

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        rcall       ADC_HANDLER

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        out         SREG, r0

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        reti

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;; Read the current 8-bit ADC sample 

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; Returns value in r16

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ADC_Read8:

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    ; Copy

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        lds         r16, ADCH

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    ; Done

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        ret

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