I2C Master logging from I2C slave with plotter support.

uno_i2c_generic_sensor_test_w_plotter.ino

#include <Wire.h>

#define ADDRESS_SLAVE 10

bool _outputPlotterOnly = false;
bool _confirmedMetadata = false;
int _packetSegment = 0;
bool _i2cNodeProcessed = false;
char _property[2][24] = {"name", "value"};

void setup() {
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  // start serial for output
  delay(1000);
  if (!_outputPlotterOnly){
    Serial.println("setup");
    Serial.println();   
  }
}

void loop() {
  if (_i2cNodeProcessed){
    if (!_confirmedMetadata){// let the slave know to start sending sensor data
      delay(1);
      Wire.beginTransmission(ADDRESS_SLAVE); 
      Wire.write(1);        
      Wire.endTransmission();    
       delay(100);
      _confirmedMetadata = true;
    }
     _i2cNodeProcessed = false;
      if (!_outputPlotterOnly){
          Serial.println();  
      } 
      return;
  }
  Wire.requestFrom(ADDRESS_SLAVE, 16);    
  _packetSegment++;
  char packet[16];
  int index = 0;
  bool isContinueSegment = false;// continueSegment (the 3rd) 1=more, 0=last
  while (Wire.available()) { // slave may send less than requested
    char c = Wire.read();
    packet[index] = int(c) > -1 ? c : ' ';// replace invalid chars with spaces      
    if (_packetSegment == 3){
      _packetSegment = 0;
      isContinueSegment = true;
//Serial.println("-------------");        
//Serial.println(int(c));        
//Serial.println("-------------");        
      if (int(c) == 48 || int(c) == 86){// 0 on last property
        _i2cNodeProcessed = true;
        // send values to MQTT
        break;
      }
    }
    index++;
  }
  if (!isContinueSegment){
      if (!_outputPlotterOnly){
          Serial.println(packet); 
      }  
      strcpy(_property[_packetSegment - 1], packet);// set local var with name/value
  }else{
    if (_outputPlotterOnly && _confirmedMetadata){
      if (_i2cNodeProcessed){
        Serial.println(_property[1]); 
      }else{
        Serial.print(_property[1]); 
        Serial.print(" "); 
      }
    }
  }
}