Documentation

// Arduino - manually talk to the ESP-01 from the Serial Monitor
// Open Serial Monitor at 9600, set "Both NL & CR" so AT commands end correctly
// Try: AT, AT+GMR (firmware version), AT+CWLAP (scan APs)

#include <SoftwareSerial.h>

SoftwareSerial esp(2, 3);   // RX = D2, TX = D3 (through divider)

void setup() {
  Serial.begin(9600);
  esp.begin(9600);          // some AT firmwares default to 115200; try both
  Serial.println("ESP-01 AT pass-through. Type commands above.");
}

void loop() {
  while (esp.available())    Serial.write(esp.read());
  while (Serial.available()) esp.write(Serial.read());
}

// Arduino - join a Wi-Fi network using ESP-01 AT commands

#include <SoftwareSerial.h>

SoftwareSerial esp(2, 3);

void send(const char* cmd, unsigned long ms = 2000) {
  Serial.print("> "); Serial.println(cmd);
  esp.println(cmd);
  unsigned long start = millis();
  while (millis() - start < ms) {
    while (esp.available()) Serial.write(esp.read());
  }
  Serial.println();
}

void setup() {
  Serial.begin(9600);
  esp.begin(9600);
  delay(500);
  send("AT");
  send("AT+CWMODE=1");                                   // station mode
  send("AT+CWJAP=\"YOUR_SSID\",\"YOUR_PASSWORD\"", 8000); // join network
  send("AT+CIFSR");                                      // print IP
}

void loop() {}

// Arduino - simple HTTP GET via ESP-01 AT commands
// Assumes the ESP-01 is already joined to Wi-Fi

#include <SoftwareSerial.h>
SoftwareSerial esp(2, 3);

void send(const String &cmd, unsigned long ms = 2000) {
  esp.println(cmd);
  unsigned long start = millis();
  while (millis() - start < ms) {
    while (esp.available()) Serial.write(esp.read());
  }
}

void setup() {
  Serial.begin(9600);
  esp.begin(9600);
  delay(500);

  send("AT+CIPSTART=\"TCP\",\"example.com\",80", 4000);

  String req = "GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n";
  send("AT+CIPSEND=" + String(req.length()), 1000);
  send(req, 4000);
  send("AT+CIPCLOSE");
}

void loop() {}