caliper sketch 2

//
//Digital caliper code to read the value off of a cheap set of digital calipers
//By Making Stuff Youtube channel https://www.youtube.com/c/makingstuff
//This code is open source and in the public domain.

const byte clockPin = 2;  //attach to clock pin on calipers
const byte dataPin = 3; //attach to data pin on calipers

//Milliseconds to wait until starting a new value
//This can be a different value depending on which flavor caliper you are using.
const int cycleTime = 50;

unsigned volatile int clockFlag = 0;

long now = 0;
long lastInterrupt = 0;
long value = 0;

float finalValue = 0;
float previousValue = 0;

int newValue = 0;
int sign = 1;
int currentBit = 1;

void setup() {
  Serial.begin(115200);
  Serial.println("void setup start");
  Serial.println("Caliper Test Sketch");
  pinMode(clockPin, INPUT);
  pinMode(dataPin, INPUT);


  //We have to take the value on the RISING edge instead of FALLING
  //because it is possible that the first bit will be missed and this
  //causes the value to be off by .01mm.
  attachInterrupt(digitalPinToInterrupt(clockPin), clockISR, RISING);
    Serial.println("void setup end");
}

void loop() {
//  Serial.println("void loop start");
  if(newValue)
  {
   if(finalValue != previousValue) {
     previousValue = finalValue;
     Serial.println(finalValue,2);
   }
   newValue = 0;
  }

 //The ISR Can't handle the arduino command millis()
 //because it uses interrupts to count. The ISR will
 //set the clockFlag and the clockFlag will trigger
 //a call the decode routine outside of an ISR.
 if(clockFlag == 1)
 {
  clockFlag = 0;
  decode();
 }

}

void decode(){
   unsigned char dataIn;
   dataIn = digitalRead(dataPin);

   now = millis();

   if((now - lastInterrupt) > cycleTime)
   {
     finalValue = (value * sign) / 100.00;
     currentBit = 0;
     value = 0;
     sign = 1;
     newValue = 1;
   }
   else if (currentBit < 16 )
   {

     if (dataIn == 0)
     {
       if (currentBit < 16) {
          value |= 1 << currentBit;
       }
       else if (currentBit == 20) {
          sign = -1;
       }

     }

     currentBit++;

   }

   lastInterrupt = now;

}

void clockISR(){
 clockFlag = 1;
}