The main loop

loop.cpp

float voltfloat = 0, currentfloat = 0, wattfloat = 0; // real unit values

float voltscalefactor = 0.0307162746 / 256;           // calibration constants vary from device to device
float currentscalefactor = 1.553 / 256000;   
float wattscalefactor = 15.49521794871 / 2560;  

// the loop function runs over and over again forever
void loop() {
  digitalWrite ( GREEN_LED, !!(millis() & 512) );           // flash the green LED
  server.handleClient();                                    // run web server
  if(new_readings) {                                        // set by interrupt when data received
    voltfloat = voltint * voltscalefactor;                  // convert to real units
    currentfloat = currentint * currentscalefactor;
    wattfloat = wattint * wattscalefactor;
    Serial.printf("V%5.1f, A%4.2f, W%5.1f", voltfloat, currentfloat, wattfloat);
    for(int i = 0; i < length; ++i)
      Serial.printf(" %02X", data[i]);
    Serial.println();
    new_readings = false;
  }
  ArduinoOTA.handle();
}