void adc_init(void)
{
//настройка АЦП
ADCSRA|=(1<<ADEN)|(1<<ADPS0)|(1<<ADPS1)|(1<<ADPS2);
ADMUX|=(1<<REFS0)|(0<<REFS1);
}


uint16_t make_single_adc_cycle(unsigned char port_number)
{
switch(port_number)
{
case 0:
ADMUX|=(0<<MUX4)|(0<<MUX3)|(0<<MUX2)|(0<<MUX1)|(0<<MUX0);
break;
case 1:
ADMUX|=(0<<MUX4)|(0<<MUX3)|(0<<MUX2)|(0<<MUX1)|(1<<MUX0);
break;
case 2:
ADMUX|=(0<<MUX4)|(0<<MUX3)|(0<<MUX2)|(1<<MUX1)|(0<<MUX0);
break;
case 3:
ADMUX|=(0<<MUX4)|(0<<MUX3)|(0<<MUX2)|(1<<MUX1)|(1<<MUX0);
break;
case 4:
ADMUX|=(0<<MUX4)|(0<<MUX3)|(1<<MUX2)|(0<<MUX1)|(0<<MUX0);
break;
case 5:
ADMUX|=(0<<MUX4)|(0<<MUX3)|(1<<MUX2)|(0<<MUX1)|(1<<MUX0);
break;
case 6:
ADMUX|=(0<<MUX4)|(0<<MUX3)|(1<<MUX2)|(1<<MUX1)|(0<<MUX0);
break;
case 7:
ADMUX|=(0<<MUX4)|(0<<MUX3)|(1<<MUX2)|(1<<MUX1)|(1<<MUX0);
break;
default:
return 0;
break;
}
ADCSRA|=(1<<ADSC);
while(!(ADCSRA & (1<<ADIF)));
ADCSRA|=(1<<ADIF);
return ADC;
}

int main (void)
{
volatile uint16_t result[4];
//...
//здесь заполняю массив данными для отправки через uart
for(unsigned char i=4; i<8; i++)
{
result[i-4]=make_single_adc_cycle(i);
}
sData[5]=result[0]>>8;
sData[6]=result[0];
sData[7]=result[1]>>8;
sData[8]=result[1];
sData[9]=result[2]>>8;
sData[10]=result[2];
sData[11]=result[3]>>8;
sData[12]=result[3];

//...