Battery Protection from Discharge

// ATtiny13
// Battery Protection from discharge
// © Grigoriev Alexander , 2016
// ADC Module

#include <avr/io.h>
#define F_CPU 8000000UL
#include <compat/deprecated.h>


#define GATE PORTB0
#define VOLT PORTB4
#define WARN PORTB3


int ReadADC();


/*
R1=100K;
R2=20K;
Vout=(R2/(R1+R2));  ~0.166667
11.1*0.16667 =
1024*1.85/5=378.88;
1024*2.03/5=415.7;
c=34.13
11.1*34.13=378.8

*/


uint16_t  LTHR = 379; //11.1
uint16_t  HTHR = 415; //12.2;

#define SRAM __attribute__((section(".noinit")))

SRAM int temp ;

void initadc()
{
    ADMUX |= (0 << REFS0); // VCC as Reference
    //
    //  MUX[1:0] Single Ended Input
    //  00 ADC0 (PB5)
    //  01 ADC1 (PB2)
    //  10 ADC2 (PB4)
    //  11 ADC3 (PB3)
    ADMUX |= (1 << MUX1) | (0 << MUX0); // ADC2 PB.4

}
int __attribute__((naked))
main (void)
{
    sbi(DDRB,GATE); //  DDRB |= (1 << GATE); // output
    sbi(PORTB,GATE); //null

    cbi(DDRB,VOLT); //  DDRB &= ~(1 << VOLT);
    cbi(PORTB,VOLT); //PORTB &= ~(1 << VOLT);

//  Bit 7 – ADEN: ADC Enable
//  Writing this bit to one enables the ADC. By writing it to zero, the ADC is turned off. Turning the
//  ADC off while a conversion is in progress, will terminate this conversion.

    initadc();
    ADCSRA |= (1 << ADEN); // Enable ADC


    while (1)
    {

        temp=ReadADC();
        if(temp<=LTHR)
        {cbi(PORTB,GATE);
         cbi(PORTB,WARN); }
        else
        if (temp>=HTHR){
        sbi(PORTB,GATE);
        cbi(PORTB,WARN);
        }
        else
        sbi(PORTB,WARN);


    }
}




int ReadADC()
{
initadc();

ADCSRA |= (1 << ADSC); // Start Converstion

    while((ADCSRA & 0x40) !=0){}; //wait for conv complete

    return ADC;
}