Hallo, das hier ist getestet und funktioniert einwandfrei:

Dim I As Byte
Dim Summe As Word
Dim Zwoelfbit As Word
Dim Zehnbit As Word

Config Adc = Single , Prescaler = Auto , Reference = Avcc

Start Adc

Do
Summe = 0

For I = 0 To 15
Zehnbit = Getadc(0)
Summe = Summe + Zehnbit
Next

Zwoelfbit = Summe / 4


Print Zwoelfbit

Loop