Read a knob on an Arduino Uno

// Analog: read a voltage on A0 and print it five times a second.
//
// Wire a potentiometer with its ends to 5 V and GND and its wiper to A0, or
// just two resistors making a divider. analogRead returns 0..1023 for 0..5 V
// against the AVCC reference: a 10-bit conversion at 125 kHz, 104 us, which
// analogRead waits out.
//
// The millivolts are worked out in integer arithmetic. There is no soft-float
// runtime here, so a sketch cannot multiply floats, but it can print one,
// and (raw * 5000) / 1023 needs nothing but a 32-bit multiply and divide.

const int SENSOR_PIN = A0;

void setup() {
  Serial.begin(115200);
  Serial.println("Mokxi Arduino Uno: analogRead on A0");
}

void loop() {
  int raw = analogRead(SENSOR_PIN);
  long millivolts = (long)raw * 5000L / 1023L;

  Serial.print("A0 = ");
  Serial.print(raw);
  Serial.print("  (");
  Serial.print(millivolts);
  Serial.println(" mV)");

  delay(200);
}