Не удается вызвать функцию при обратном вызове для onRequest()

Я НУБ! Попытка использовать модуль ZS-042 RTC для получения текущего времени и отправки его обратно в RPi по I2C. Я могу вызвать функцию и перевести ее в последовательный режим, но когда я пытаюсь вызвать функцию для обновления глобальных переменных из функции обратного вызова для onRequest (), происходит сбой Ardiuno (Micro).

#include <Wire.h>

// LED on pin 13
const int TEMP_PIN1 = A0;
const int RELAY_PIN1 = 4;
const int SAMPLE_TIME = 100;
const byte RPI_I2C_ADDRESS = 0x08;
const int DS3231_I2C_ADDRESS = 0x68;

byte number = 0;
byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;

/*
 * RTC Setup
 */
// Convert normal decimal numbers to binary coded decimal
byte decToBcd(byte val)
{
  return( (val/10*16) + (val%10) );
}
// Convert binary coded decimal to normal decimal numbers
byte bcdToDec(byte val)
{
  return( (val/16*10) + (val%16) );
}
void setDS3231time(byte second, byte minute, byte hour, byte dayOfWeek, byte
      dayOfMonth, byte month, byte year)
{
  // sets time and date data to DS3231
  Wire.beginTransmission(DS3231_I2C_ADDRESS);
  Wire.write(0); // set next input to start at the seconds register
  Wire.write(decToBcd(second)); // set seconds
  Wire.write(decToBcd(minute)); // set minutes
  Wire.write(decToBcd(hour)); // set hours
  Wire.write(decToBcd(dayOfWeek)); // set day of week (0=Sunday, 6=Saturday)
  Wire.write(decToBcd(dayOfMonth)); // set date (1 to 31)
  Wire.write(decToBcd(month)); // set month
  Wire.write(decToBcd(year)); // set year (0 to 99)
  Wire.endTransmission();
}

/*
void readDS3231time(byte *second,
    byte *minute,
    byte *hour,
    byte *dayOfWeek,
    byte *dayOfMonth,
    byte *month,
    byte *year)
{
  Wire.beginTransmission(DS3231_I2C_ADDRESS);
  Wire.write(0); // set DS3231 register pointer to 00h
  Wire.endTransmission();
  Wire.requestFrom(DS3231_I2C_ADDRESS, 7);
  // request seven bytes of data from DS3231 starting from register 00h
  *second = bcdToDec(Wire.read() & 0x7f);
  *minute = bcdToDec(Wire.read());
  *hour = bcdToDec(Wire.read() & 0x3f);
  *dayOfWeek = bcdToDec(Wire.read());
  *dayOfMonth = bcdToDec(Wire.read());
  *month = bcdToDec(Wire.read());
  *year = bcdToDec(Wire.read());
}
*/

void readDS3231time()
{
  Wire.beginTransmission(DS3231_I2C_ADDRESS);
  Wire.write(0); // set DS3231 register pointer to 00h
  Wire.endTransmission();
  Wire.requestFrom(DS3231_I2C_ADDRESS, 7);
  // request seven bytes of data from DS3231 starting from register 00h
  second = bcdToDec(Wire.read() & 0x7f);
  minute = bcdToDec(Wire.read());
  hour = bcdToDec(Wire.read() & 0x3f);
  dayOfWeek = bcdToDec(Wire.read());
  dayOfMonth = bcdToDec(Wire.read());
  month = bcdToDec(Wire.read());
  year = bcdToDec(Wire.read());
}


void displayTime()
{
  //byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
  // retrieve data from DS3231
  //readDS3231time(&second, &minute, &hour, &dayOfWeek, &dayOfMonth, &month, &year);
  readDS3231time();
  // send it to the serial monitor
  Serial.print(hour, DEC);
  // convert the byte variable to a decimal number when displayed
  Serial.print(":");
  if (minute<10)
  {
    Serial.print("0");
  }
  Serial.print(minute, DEC);
  Serial.print(":");
  if (second<10)
  {
    Serial.print("0");
  }
  Serial.print(second, DEC);
  Serial.print(" ");
  Serial.print(dayOfMonth, DEC);
  Serial.print("/");
  Serial.print(month, DEC);
  Serial.print("/");
  Serial.print(year, DEC);
  Serial.print(" Day of week: ");
  switch(dayOfWeek){
  case 0:
    Serial.println("Sunday");
    break;
  case 1:
    Serial.println("Monday");
    break;
  case 2:
    Serial.println("Tuesday");
    break;
  case 3:
    Serial.println("Wednesday");
    break;
  case 4:
    Serial.println("Thursday");
    break;
  case 5:
    Serial.println("Friday");
    break;
  case 6:
    Serial.println("Saturday");
    break;
  }
}


void flash_data(int loops)
{ 
   for (int i = 0; i < loops; i++)
   {
      digitalWrite(LED_BUILTIN, HIGH);
      Serial.println("LED Pin HIGH: "+String(digitalRead(LED_BUILTIN)));
      delay(50);
      digitalWrite(LED_BUILTIN, LOW);
      Serial.println("LED Pin LOW: "+String(digitalRead(LED_BUILTIN)));
      delay(50);
   }
}

// callback for received data
void receiveData(int byteCount)
{
  Serial.println("Receiving Data... ");
  if ( Wire.available() ) {
    number = Wire.read();
  }
  Serial.println("Data Received: "+String(number));
}

void sendData() {
  Serial.println("Sending Data on Request");
  //byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
  // retrieve data from DS3231
  //readDS3231time(&second, &minute, &hour, &dayOfWeek, &dayOfMonth, &month, &year);
  readDS3231time();
  //char buf1[20];
  //sprintf(buf1, "%02d:%02d:%02d %02d/%02d/%02d",  hour, minute, second, dayOfMonth, month, year);
  //Serial.print(buf1);
  Wire.write("Hello");  
}

void setup() {
  Serial.begin(57600);
  do {
    delay(500);
  } while (!Serial);

  delay(500);
  Serial.println("Initializing Wire I2C on "+RPI_I2C_ADDRESS);
  // Join I@c bus as slave with RPI_I2C_ADDRESS 8
  Wire.begin(RPI_I2C_ADDRESS);


  Serial.println("Setting call back for Wire.onReceive");
  Wire.onReceive(receiveData);
  Wire.onRequest(sendData);

  //Setup pin 13 as output and turn LED off
  Serial.println("Setting LED Pin up for Output");
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(RELAY_PIN1, OUTPUT);
  pinMode(TEMP_PIN1, INPUT);
  Serial.println("Turning LED off");
  digitalWrite(LED_BUILTIN, LOW);
}

float getVoltage(int pin)
{
  // This function has one input parameter, the analog pin number
  // to read. You might notice that this function does not have
  // "void" in front of it; this is because it returns a floating-
  // point value, which is the true voltage on that pin (0 to 5V).
  return (analogRead(pin) * 0.004882814);
  // This equation converts the 0 to 1023 value that analogRead()
  // returns, into a 0.0 to 5.0 value that is the true voltage
  // being read at that pin.
}


/*
 * MAIN LOOP
 */
void loop() {

  if ( number > 0 ) {
    //Serial.println("Flash Data: "+String(number));
    flash_data(number);
    float voltage, avgVoltage, degreesC, degreesF;
    if (number == 1) {
      digitalWrite(RELAY_PIN1, HIGH);
    } else if (number == 2) {
      digitalWrite(RELAY_PIN1, LOW);
    } else if ( number == 3 ) {
      voltage = getVoltage(TEMP_PIN1);
      //gets and prints the raw data from the lm35
      Serial.print("Voltage: ");
      Serial.print (voltage);
      Serial.println(" ");
      // Now we'll convert the voltage to degrees Celsius.
      // This formula comes from the temperature sensor datasheet:
      degreesC = (voltage - 0.48) * 100.0;
      Serial.print("CELSIUS: ");
      Serial.print(degreesC);
      Serial.println("*C ");
      //converts celsius into fahrenheit 
      degreesF = degreesC * (9.0/5.0) + 32.0;
      Serial.print("FAHRENHEIT: ");
      Serial.print(degreesF);
      Serial.println("*F");
    } else if ( number == 4 ) {
       displayTime();
    }
    number = 0;
  } else {
    byte pinValue = bitRead(LED_BUILTIN, 3);
    if ( digitalRead(LED_BUILTIN) == HIGH ) {
      digitalWrite(LED_BUILTIN, LOW);
    }
  }
  delay(SAMPLE_TIME);
}

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