Aref uses an external reference of 1.024v and the sampling channel is ADC1 with a sampling voltage of 0.5v. But no matter how the sampling voltage changes, the value sampled back by ADC is always 1023, where could the problem be?
Code:
unsigned int MCU_ADC_READ(unsigned char channel){
unsigned char Sample_avgCn;
unsigned int ret,tota=1;
ADMUX&=~((1<<MUX0)|(1<<MUX1)|(1<<MUX2)|(1<<MUX3));//Clear MUX bits
ADMUX|=channel;//MUX set
ADCSRA|=(1<<ADSC)|(1<<ADEN);//Start a conversion
while(ADCSRA&(1<<ADSC));//dump first result
ADCSRA|=(1<<ADEN);
for(Sample_avgCn=0;Sample_avgCn<8;Sample_avgCn++){//read 8 times
ADCSRA|=(1<<ADSC);
while(ADCSRA&(1<<ADSC));
ret=ADCL;
ret|=(unsigned int)(ADCH<<8);
tota+=ret;
}
ADCSRA = 0; //Turn OFF internal ADC
return tota>>3;//averaging by 8
}
