I have written a little program which should (at the end) host a little website. This is just my setup. But for some reason, it writes "srl?" endlessly onto the serial monitor. I just connected the ESP8266-01 to my Arduino UNO, using 115200 baud with the nodeMCU board. Using different boards results in an error telling me I should use nodeMCU.

As I have written in the title, I do not understand how it can produce an endless output without a loop with Serial.print/write in it.

#include <ESP8266WiFi.h>

const char* NAME = "x"; //ssid
const char* PWRT = "x"; //password

WiFiServer server(80);

void setup() {

  Serial.printf("connect with %s \n", NAME);
  WiFi.begin(NAME, PWRT);

  while (WiFi.status() != WL_CONNECTED) {

  Serial.printf("webserver open, access with %s\n", WiFi.localIP().toString().c_str());

void loop() {
  // put your main code here, to run repeatedly:

  • 1
    "I just connected the ESP8266-01 to my Arduino UNO, using 115200 baud with the nodeMCU board". What NodeMCU board? The ESP8266-01 is not a NodeMCU. How did you connect everything up? If your Arduino uses SoftwareSerial to communicate with the ESP8266-01 at 115200 baud, that will not work reliably. Use 9600 baud.
    – StarCat
    Aug 19, 2020 at 15:02
  • 1
    you have a reset loop
    – Juraj
    Aug 19, 2020 at 15:05
  • 1
    What do you mean @Juraj?
    – Max
    Aug 19, 2020 at 15:15
  • @StarCat like this virtuino.com/images/arduino_esp8266_connections.png but to RX and TX instead of Pin 2 and 3
    – Max
    Aug 19, 2020 at 15:19
  • 1
    You need to show the actual output. "Word salad" could be anything. For example, are the words ""connect with" and "webserver open, access with" part of this salad?
    – Nick Gammon
    Aug 20, 2020 at 23:09

1 Answer 1


The ESP8266WiFi.h is for running on an ESP8266 host, but your are trying to use it on an Arduino Uno. This caused the crash of your sketch on Arduino Uno.

Based on the connection diagram you provided, you are using the ESP-01 as an wifi-shield and the ESP-01 by default is having an AT commands firmware. In order to use the ESP-01 as a wifi shield, you need an library like WiFiEspAT.

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