(name of the project) went disconnected after connected for one minute

my project name is Nurse Center, i’m using NodeMCU and android as the device. the project can connected to the blynk apps but after one minute working there is a message “Nurse Center disconnected”. and after that I can’t connect the project again. anyone can help me to solve the problem?

here is my code:

#include <Ticker.h>
#include <ESP8266WiFi.h>
#include <Blynk.h>
#include <BlynkSimpleEsp8266.h>

#include <ESP8266WiFi.h>
#include <Wire.h>

char auth[] = "";
char ssid[] = "";
char pass[] = "";

// The Ticker/flipper routine
Ticker flipper;

int blinkPin = 15;                // pin to blink led at each beat
int fadePin = 12;                 // pin to do fancy classy fading blink at each beat
int fadeRate = 0;                 // used to fade LED on with PWM on fadePin
unsigned long Time;

// these variables are volatile because they are used during the interrupt service routine!
volatile int BPM;                   // used to hold the pulse rate
volatile int Signal;                // holds the incoming raw data
volatile int IBI = 600;             // holds the time between beats, must be seeded! 
volatile boolean Pulse = false;     // true when pulse wave is high, false when it's low
volatile boolean QS = false;        // becomes true when Arduoino finds a beat.

// For the display

void setup(){
  pinMode(blinkPin,OUTPUT);         // pin that will blink to your heartbeat!
  pinMode(fadePin,OUTPUT);          // pin that will fade to your heartbeat!
  Serial.begin(9600);             // we agree to talk fast!
  Serial.println("Connecting to : ");
  WiFi.begin(ssid, pass); //memulai menghubungkan perangkat ke WiFi
  //cek WiFi status
  while (WiFi.status() != WL_CONNECTED){
  Serial.println("WiFi Connected");
  Serial.print("IP address : ");
  interruptSetup();                 // sets up to read Pulse Sensor signal every 2mS
  Time = millis();

  Blynk.begin(auth, ssid, pass); //aplikasi blynk bersiap memulai

void loop(){

  Blynk.run(); //aplikasi blynk bekerja
    unsigned long previousTime = millis();
    if (previousTime - Time >= 1000){
      Time = previousTime;     
      Serial.print(" BPM = ");
      Serial.print("  IBI = ");

      //aplikasi blynk menampilkan pembacaan detak jantung
      Blynk.virtualWrite(V1, BPM);
      Blynk.virtualWrite(V0, BPM);

and this is the code for the interrupt:

volatile int rate[10];                    // array to hold last ten IBI values
volatile unsigned long sampleCounter = 0; // used to determine pulse timing
volatile unsigned long lastBeatTime = 0;  // used to find IBI
volatile int P =512;                      // used to find peak in pulse wave, seeded
volatile int T = 512;                     // used to find trough in pulse wave, seeded
volatile int thresh = 512;                // used to find instant moment of heart beat, seeded
volatile int amp = 100;                   // used to hold amplitude of pulse waveform, seeded
volatile boolean firstBeat = true;        // used to seed rate array so we startup with reasonable BPM
volatile boolean secondBeat = false;      // used to seed rate array so we startup with reasonable BPM

void interruptSetup(){     
// Initializes Ticker to have flipper run the ISR to sample every 2mS as per original Sketch.
  flipper.attach_ms(2, ISRTr);     

// Ticker makes sure that we take a reading every 2 miliseconds
void ISRTr(){                         // triggered when flipper fires....
  cli();                               // disable interrupts while we do this
  Signal = analogRead(A0);              // read the Pulse Sensor 
  sampleCounter += 2;                         // keep track of the time in mS with this variable
  int N = sampleCounter - lastBeatTime;       // monitor the time since the last beat to avoid noise

    //  find the peak and trough of the pulse wave
  if(Signal < thresh && N > (IBI/5)*3){       // avoid dichrotic noise by waiting 3/5 of last IBI
    if (Signal < T){                        // T is the trough
      T = Signal;                         // keep track of lowest point in pulse wave 

  if(Signal > thresh && Signal > P){          // thresh condition helps avoid noise
    P = Signal;                             // P is the peak
  }                                        // keep track of highest point in pulse wave

  // signal surges up in value every time there is a pulse
  if (N > 250){                                   // avoid high frequency noise
    if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ){        
      Pulse = true;                               // set the Pulse flag when we think there is a pulse
      digitalWrite(blinkPin,HIGH);                // turn on pin 13 LED
      IBI = sampleCounter - lastBeatTime;         // measure time between beats in mS
      lastBeatTime = sampleCounter;               // keep track of time for next pulse

      if(secondBeat){                        // if this is the second beat, if secondBeat == TRUE
        secondBeat = false;                  // clear secondBeat flag
        for(int i=0; i<=9; i++){             // seed the running total to get a realisitic BPM at startup
          rate[i] = IBI;                      

      if(firstBeat){                         // if it's the first time we found a beat, if firstBeat == TRUE
        firstBeat = false;                   // clear firstBeat flag
        secondBeat = true;                   // set the second beat flag
        sei();                               // enable interrupts again
        return;                              // IBI value is unreliable so discard it

      // keep a running total of the last 10 IBI values
      word runningTotal = 0;                  // clear the runningTotal variable    

      for(int i=0; i<=8; i++){                // shift data in the rate array
        rate[i] = rate[i+1];                  // and drop the oldest IBI value 
        runningTotal += rate[i];              // add up the 9 oldest IBI values

      rate[9] = IBI;                          // add the latest IBI to the rate array
      runningTotal += rate[9];                // add the latest IBI to runningTotal
      runningTotal /= 10;                     // average the last 10 IBI values 
      BPM = 60000/runningTotal;               // how many beats can fit into a minute? that's BPM!
      QS = true;                              // set Quantified Self flag 

  if (Signal < thresh && Pulse == true){   // when the values are going down, the beat is over
    digitalWrite(blinkPin,LOW);            // turn off pin 13 LED
    Pulse = false;                         // reset the Pulse flag so we can do it again
    amp = P - T;                           // get amplitude of the pulse wave
    thresh = amp/2 + T;                    // set thresh at 50% of the amplitude
    P = thresh;                            // reset these for next time
    T = thresh;

  if (N > 2500){                           // if 2.5 seconds go by without a beat
    thresh = 512;                          // set thresh default
    P = 512;                               // set P default
    T = 512;                               // set T default
    lastBeatTime = sampleCounter;          // bring the lastBeatTime up to date        
    firstBeat = true;                      // set these to avoid noise
    secondBeat = false;                    // when we get the heartbeat back

  sei();                                   // enable interrupts when youre done!
}// end isr

First of all, you should read this

You’re establishing a WiFi connection, then calling Blynk.begin().

You shouldn’t be doing both of these. I’d suggest that you read the Blynk Legacy documentation about this here:

Also, I’m confused by what you refer to as the interrupt.
I assume that this code it meant to simulate pulse readings using the ticker as a timer, rather than actually take readings, ad that the so called interrupt service routine is actually just a software pulse generator?