read reference voltage ATTiny202

[jazzjohn27]

The following reads the 0.55V internal voltage reference correctly. However if analogReference(INTERNAL2V5) is called to set the 2.5V reference, the reading is 1023. How can the other voltage references be read while using Vdd as the reference?

int x;
void setup(){
pinMode(0,OUTPUT);
//analogReference(INTERNAL2V5);
Serial.begin(9600);
while(!Serial) ;;;
}

void loop()
{
Serial.print("Reference: ");
x =analogRead(ADC_INTREF);
Serial.println(x);
delay(1000);
}

[jazzjohn27]

Just found a way by using init_ADC0()

int x;
void setup(){
pinMode(P2,OUTPUT);
analogReference(INTERNAL2V5);
Serial.begin(9600);
while(!Serial) ;;;
init_ADC0(); // this makes it work
}

void loop()
{
Serial.print("Reference: ");
x =analogRead(ADC_INTREF);
Serial.println(x );
delay(1000);
}

[SpenceKonde]

Aaaaah yeah - the trick here is to do

analogReference(INTERNAL2V5); //Sets the reference voltage to 2V5 and sets the ADC to use that reference. 
analogReference(VCC); // sets the ADC to use VDD as reference - but the reference is still set to 2.5V

[SpenceKonde]

I'll amend Ref_Analog.md