wifi_lux_sensor/wifi_lux_sensor.ino

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

const char* ssid = "Hemnet3";
const char* password = "";

WiFiClient espClient;

void connectWifi() {
  Serial.print("Connecting to ");
  Serial.println(ssid);
    // temporary fix until SDK 1.5.4 is used
  WiFi.persistent(false);
  WiFi.mode(WIFI_OFF);
  WiFi.mode(WIFI_STA);
    // temporary fix end
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
      delay(1000);
      Serial.print(WiFi.status());
      Serial.print(".");
  }
  
  Serial.println("");
  Serial.print("Connected with IP: "),
  Serial.println(WiFi.localIP());
}

void setup() {
  Serial.begin(115200); //Opens USB-Serial connection for terminal
  delay(5000);
  Serial.print("Serial interface is ready\r\n");
  connectWifi();
  Wire.begin(4, 5); // sda on pin D2, scl on pin D1
}

void loop() {
  // put your main code here, to run repeatedly:
  byte error, address;
  int nDevices;
  
  Serial.print("WiFi heartbeat - ms since boot: ");
  Serial.print(millis());
  Serial.println();
  Serial.println("Scanning i2c devices... ");

  nDevices = 0; 
  for(address = 1; address < 127; address++) {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address<16)
        Serial.print("0");
      Serial.print(address,HEX);
      Serial.println("  !");
 
      nDevices++;
    }
    else if (error==4) {
      Serial.print("--Unknown error at address 0x");
      if (address<16)
        Serial.print("0");
      Serial.println(address,HEX);
    }    
  }
  if (nDevices == 0)
    Serial.println("--No I2C devices found\n");
  else
    Serial.println("done\n");
 
  delay(1000);
  
}