#include "Wire.h"

const byte I2C_SLAVE_ADDR = 0x20;

void setup()
{
   Serial.begin(115200);

   Wire.begin(I2C_SLAVE_ADDR);
   Wire.onReceive(receiveEvent);
   Wire.onRequest(requestEvent);
}

long data = 0;
long response = 200;

void receiveEvent(int bytes)
{
   data = 0;
   uint8_t index = 0;
   while (Wire.available())
   {
      byte* pointer = (byte*)&data;
      *(pointer + index) = (byte)Wire.read();
      index++;
   }
}

void requestEvent()
{
   Wire.write((byte*)&response, sizeof(response));
}


void loop() {

   if (data != 0)
   {
      Serial.println(data);
      data = 0;
   }
}