how to know when a EEPROM address is empty?

Projects Programming
8

John
That worked like a charm. I am using this with an encoder that is setting the Target. In the past I had to load the code twice for every virgin unit. I wish you taught me this earlier... than you,

Mitch

Here is my code with the encoder

#include <EEPROM.h>

float Target;

float AddToTarget;

#include <Encoder.h>

long positionKnob  = -999;
long  newKnob;
Encoder Knob(18, 19); // 18 is Yellow 19 is Green

void setup()
{
  Serial.begin(115200);
  while (!Serial) {}
  Serial.println();

  EEPROM.get(0, Target);

  Serial.print(F("Read value of Target is "));
  Serial.println (Target);

  if (isnan(Target))
  {
    Serial.println(F("Target is 'nan' so initialize."));
    Target = 8.88;
    Serial.print(F("Initialized value of Target is "));
    Serial.println (Target);
    EEPROM.put(0, Target);
  }

}

void loop(){ /* Empty loop */

   newKnob = Knob.read();
    if (newKnob != positionKnob) {

      positionKnob = newKnob;
    AddToTarget = (newKnob / 10.0);
      

      Target = (Target + AddToTarget);
      Target = constrain(Target, 1, 10000);
      Serial.print(" KNOB = ");
      Serial.println(newKnob);
      Serial.print("   Target = ");
      Serial.print(Target, 2);
      Serial.println();
      Knob.write(0);

       EEPROM.put(0, Target);
    
    }
  Serial.println (Target);
  delay (500);
  }