i've been working on a project that im using an esp8266 nodemcu-01 as described in the title, and i've been having some headache with this module, first because after searching i figured out that the commands LOW and HIGH are inversed as in LOW outputs 3.3v e HIGH outputs low tension, so i began to grow worried about the possibility that other programming resources may follow the same situation. But with that problem a part, i've been trying a few different codes including the one found in the sketchbook examples and still couldn't connect.

Also another weird problem, is that i was working working with the baudrate set on the arduino IDE settings on 115200, and so is the Serial.begin, that is also set to 115200, however i can only read properly the continuous dot that is contained in the while loop "........." when i set it to 74880, which another thing that i was trying to understand. I also forgot to mention that it keeps spamming dots but does not connect at all.

And to conclude, my problem resumes in not being able to connect to any wifi i've tried, i tried my friend's home and also 4g, both did not work, here's the code, which we tried first:

#include <ESP8266WiFi.h>

char* ssid = "Net Wi-fi";
char* password = "testingtest";
void setup() {
  WiFi.begin(ssid, password);

void loop(){

This was the original try, using the arduino sketch example:

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>

const char* ssid = "Net6271";
const char* password = "megaman"; 

ESP8266WebServer server(80);

const int led = 13;

void handleRoot() {
  digitalWrite(led, 1);
  server.send(200, "text/plain", "hello from esp8266!");
  digitalWrite(led, 0);

void handleNotFound(){
  digitalWrite(led, 1);
  String message = "File Not Found\n\n";
  message += "URI: ";
  message += server.uri();
  message += "\nMethod: ";
  message += (server.method() == HTTP_GET)?"GET":"POST";
  message += "\nArguments: ";
  message += server.args();
  message += "\n";
  for (uint8_t i=0; i<server.args(); i++){
    message += " " + server.argName(i) + ": " + server.arg(i) + "\n";
  server.send(404, "text/plain", message);
  digitalWrite(led, 0);

void setup(void){
  pinMode(led, OUTPUT);
  digitalWrite(led, 0);
  WiFi.begin(ssid, password);

  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
  Serial.print("Connected to ");
  Serial.print("IP address: ");

  if (MDNS.begin("esp8266")) {
    Serial.println("MDNS responder started");

  server.on("/", handleRoot);

  server.on("/inline", [](){
    server.send(200, "text/plain", "this works as well");


  Serial.println("HTTP server started");

void loop(void){

Board setting: Generic ESP8266 Module. Crystal Frequency: 40MHz. Flash Frequency: 80Mhz. Upload Speed: 115200. Flash Mode: DIO. Flash Size: 512k no SPIFFS.

pls help.


1 Answer 1


ESP-01 modules use 26 MHz crystal. Set the Crystal frequency in IDE to 26 MHz.

Both io pins (0 and 2) on esp-01 have pull-up circuit. That is why you think you measured 'inverted' logic.

  • Thank you for replying my good sir, when you suggest setting the crystal frequency to 26Mhz i assume that's the fix for the baud differences in serial monitor? Also, on the second post i assume its referred to the inversion of logic? thanks but what do i do about wifi not connecting? it keeps sending "." and does not connect.
    – John Jones
    Commented Jun 22, 2018 at 18:20
  • erase the flash with esptool and the try again the sketch
    – Juraj
    Commented Jun 22, 2018 at 18:34
  • Thank you sir, you are a true legend, thanks for helping me out, your suggestion worked perfectly :)
    – John Jones
    Commented Jun 22, 2018 at 22:59

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