// MACRO-START * MACRO-START * MACRO-START * MACRO-START * MACRO-START * MACRO-START *
// a detailed explanation how these macros work is given in this tutorial
// https://forum.arduino.cc/t/comfortable-serial-debug-output-short-to-write-fixed-text-name-and-content-of-any-variable-code-example/888298

#define dbg(myFixedText, variableName) \
  Serial.print( F(#myFixedText " "  #variableName"=") ); \
  Serial.println(variableName);

#define dbgi(myFixedText, variableName,timeInterval) \
  { \
    static unsigned long intervalStartTime; \
    if ( millis() - intervalStartTime >= timeInterval ){ \
      intervalStartTime = millis(); \
      Serial.print( F(#myFixedText " "  #variableName"=") ); \
      Serial.println(variableName); \
    } \
  }

#define dbgc(myFixedText, variableName) \
  { \
    static long lastState; \
    if ( lastState != variableName ){ \
      Serial.print( F(#myFixedText " "  #variableName" changed from ") ); \
      Serial.print(lastState); \
      Serial.print( F(" to ") ); \
      Serial.println(variableName); \
      lastState = variableName; \
    } \
  }

#define dbgcf(myFixedText, variableName) \
  { \
    static float lastState; \
    if ( lastState != variableName ){ \
      Serial.print( F(#myFixedText " "  #variableName" changed from ") ); \
      Serial.print(lastState); \
      Serial.print( F(" to ") ); \
      Serial.println(variableName); \
      lastState = variableName; \
    } \
  }
// MACRO-END * MACRO-END * MACRO-END * MACRO-END * MACRO-END * MACRO-END * MACRO-END *

float Quellspannung = 5.0;
int AnalogPin = 5;
float R1 = 1500.0; //Wert des bekannten Widerstands (der mitgelieferte 1,5k-Widerstand)
long Messwert;
float SpannungR2; //Spannung über dem zu messenden Widerstand
float Widerstand;

void setup() {
  Serial.begin(9600);
  Serial.println("Widerstand ausmessen");
  Serial.println();
}

void loop() {
  //5 Messungen machen und Mittelwert bilden
  Messwert = 0;
  for(int i = 0; i < 5; i++){
    Messwert += analogRead(AnalogPin);
    dbg("01",Messwert);
  }

  Messwert = Messwert / 5;
  dbg("02",Messwert);

  //Spannung berechnen
  dbg("03",Quellspannung);
  dbg("04",Quellspannung / 1023.0);
  dbg("05",(Quellspannung / 1023.0) * Messwert);
  dbg("06",SpannungR2);

  SpannungR2 = (Quellspannung / 1023.0) * Messwert;
  Serial.print("Spannung ueber R2 betraegt ");
  Serial.print(SpannungR2,2);
  Serial.println(" Volt!");
  //Berechnung: (R2 = R1 * (U2/U1))

  dbg("07",R1);
  dbg("08",SpannungR2);
  dbg("09",(Quellspannung - SpannungR2));
  dbg("10",(SpannungR2 / (Quellspannung - SpannungR2)));
  dbg("11",R1 * (SpannungR2 / (Quellspannung - SpannungR2)));

  Widerstand = R1 * (SpannungR2 / (Quellspannung - SpannungR2));
  dbg("12",Widerstand);

  Serial.print("Der Widerstand hat ");
  Serial.print(Widerstand,2);
  Serial.println(" Ohm.");
  Serial.println();
  delay(1000);
}