Flood indicator

IoT-Flood-Indicator.ino

#include "ThingSpeak.h"
#include <ESP8266WiFi.h>

const int trig = D1;
const int echo = D2;
#define redLed D3
#define grnLed D4

unsigned long channelID = REPLACE_WITH_YOUR_THINGSPEAK_CHANNEL_ID;
const char * write_api = "REPLACE_WITH_YOUR_THINGSPEAK_WRITE_API_KEY";
char auth[] = "REPLACE_WITH_YOUR_THINGSPEAK_AUTHOR";
char ssid[] = "REPLACE_WITH_YOUR_WIFI_SSID";
char pass[] = "REPLACE_WITH_YOUR_WIFI_PASSWORD";
unsigned long startMillis;
unsigned long currentMillis;
const unsigned long period = 10000;
WiFiClient  client;
long duration;
int distance;

void setup()
{
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(redLed, OUTPUT);
  pinMode(grnLed, OUTPUT);
  digitalWrite(redLed, LOW);
  digitalWrite(grnLed, LOW);
  Serial.begin(9600);
  WiFi.begin(ssid, pass);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println("WiFi connected");
  Serial.println(WiFi.localIP());
  ThingSpeak.begin(client);
  startMillis = millis();  //initial start time
}

void loop()
{
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  duration = pulseIn(echo, HIGH);
  distance = duration * 0.034 / 2;
  Serial.println(distance);
  if (distance <= 4)
  {
    digitalWrite(redLed, HIGH);
    digitalWrite(grnLed, LOW);
  }
  else
  {
    digitalWrite(grnLed, HIGH);
    digitalWrite(redLed, LOW);
  }
  currentMillis = millis();
  if (currentMillis - startMillis >= period)
  {
    ThingSpeak.setField(1, distance);
    ThingSpeak.writeFields(channelID, write_api);
    startMillis = currentMillis;
  }
}