12bitarduino.ino

// the setup routine runs once when you press reset:
void setup() {
    //Set pins 8, 9, 10, and 11 (lower bits of Port B) to output
    DDRB = 0x3F;
    //set the reference voltage to match the scale of the input signal
    analogReference(INTERNAL);
}
// the loop routine runs over and over again forever:
void loop() {
    // read the input on analog pin 0:
    int sensorValue = analogRead(A0);
    // Convert the analog reading (12 bits) to a 6 bit value:
    int output = (int)(sensorValue * 0.015384); // 63/4095
    //output the 6 bit value to the DAC
    PORTB = output & 0x3F;
}