Different analog ref same result


I am trying to increase my sensor reading on Mega but I could not.
Actually it is a custom board with Nick Gammon's bootloader.

I am changing analog reference to INTERNAL1V1 and INTERNAL2V56 but all cases i am getting the same result around 110.

What cause this situation?
Is there any bug?


Changing Internal reference is one thing but you also need to change it in your code, it's no more VREF = 5V but 1.1V or 2.56V.

I didn't understand

My code is something like below

void setup() {




void loop() {

senseResult = analogRead(A5);

  • Serial.println(senseResult[0]);*
    For default reference, for example 1V, should produce 205 value. For 2V56 reference, same voltage level should be around 400 val. Am I thinking wrong?
    For my case, each reference producing the same 110 value.

Ok I found the problem.
I've connected the Aref pin to VCC. Even I dont use external reference, it is affecting the result which is independent from the internal reference declaration.

So, if anyone sees the same result even declared internal voltage reference, if there is something connected to Aref, analog reference is being that voltage.


By forcing the Aref pin to output 1.1volt or 2.56volt, and connecting it to 5volt, you might have destroyed the Aref pin.
There is a warning for that on the Aref page.