Using ESP8266 WiFi Scan to Open WiFi scan code with Arduino -Example 2

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Project Details

This code is to use ESP8266, NodeMCU, Wemos D1 Mini to diplay all available access points (WiFi ) on serial monitor.
In this page I have provided 3 different Arduiono codes:
1-Basic WiFi scan
2-Display Open WiFo only (this code)
3-Advanced WiFi scan

Displays only Access Points that have no password

See Using ESP8266 WiFi Scan to see all available WiFi AP with Arduino -Example 1
See Using ESP8266 Advanced WiFi scan code with Arduino -Example 3

Project Code

 * Using ESP8166 Di Mini, NodeMCU to display only Open WiFi Networks
 * and display on Serial Monitor
 * Written by Ahmad Shamshiri 
 * on Aug 08, 2019 at 21:45 in Ajax, Ontario, Canada

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  * This code is "AS IS" without warranty or liability. Free to be used as long as you keep this note intact.* 
 * This code has been download from
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see .
#include "ESP8266WiFi.h"

const int RSSI_MAX =-50;// define maximum straighten of signal in dBm
const int RSSI_MIN =-100;// define minimum strength of signal in dBm

int openNetworkCount=0;// do not change. used inside loop

void setup() {
  Serial.println("Robojax Wifi Signal Scan");
  // Set WiFi to station mode and disconnect from an AP if it was previously connected

  Serial.println("Setup done");

void loop() {
  Serial.println("Wifi scan started");

  // WiFi.scanNetworks will return the number of networks found
  int n = WiFi.scanNetworks();
  Serial.println("Wifi scan ended");
  if (n == 0) {
    Serial.println("no networks found");
  } else {
    Serial.println(" networks found");
    for (int i = 0; i < n; ++i) {
      // Print SSID and RSSI for each network found
      if(WiFi.encryptionType(i) == ENC_TYPE_NONE)
      Serial.print(") ");
      Serial.print(WiFi.SSID(i));// SSID
      Serial.print(WiFi.RSSI(i));//Signal strength in dBm  
      Serial.print("dBm (");

      Serial.print(dBmtoPercentage(WiFi.RSSI(i)));//Signal strength in %  
      Serial.print("% )");
      }// if 


  // Wait a bit before scanning again
openNetworkCount =0;//reset open network counts  
}// loop

 * Written by Ahmad Shamshiri
  * with lots of research, this sources was used:
 * This is approximate percentage calculation of RSSI
 * Wifi Signal Strength Calculation
 * Written Aug 08, 2019 at 21:45 in Ajax, Ontario, Canada

int dBmtoPercentage(int dBm)
  int quality;
    if(dBm <= RSSI_MIN)
        quality = 0;
    else if(dBm >= RSSI_MAX)
        quality = 100;
        quality = 2 * (dBm + 100);

     return quality;

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