Add WiFi to Arduino Uno

Wire the WiFi module with voltage dividers.

1. Connect ESP8266 GND to Arduino GND (black wire).
2. Connect ESP8266 VCC to Arduino 3.3V with 10kΩ resistor (red wire).
3. Connect ESP8266 CH_EN to Arduino 3.3V with 10kΩ resistor (red wire).
4. Create voltage divider for RX: connect 1kΩ resistor from Arduino Pin 2 to ESP8266 RX, then 1kΩ from RX to GND.
5. Connect ESP8266 TX directly to Arduino Pin 3 (green wire).
6. Important: ESP8266 is 3.3V—do NOT connect to 5V!

Program Arduino to talk to ESP8266.

1. Download the ESP8266 WiFi sketch from project source.
2. Open in Arduino IDE.
3. Upload to Arduino Uno.
4. Sketch uses SoftwareSerial to communicate with ESP8266.

#include <SoftwareSerial.h>

SoftwareSerial esp8266(3, 2);

void setup() {
  Serial.begin(9600);
  esp8266.begin(9600);
  
  Serial.println("ESP8266 WiFi Test");
  
  sendCommand("AT", 1000);
  sendCommand("AT+CWMODE=1", 1000);
  sendCommand("AT+CWJAP=\"YOUR_SSID\",\"YOUR_PASSWORD\"", 5000);
  sendCommand("AT+CIFSR", 2000);
}

void loop() {
  if (esp8266.available()) {
    Serial.write(esp8266.read());
  }
  
  if (Serial.available()) {
    esp8266.write(Serial.read());
  }
}

void sendCommand(String cmd, int wait) {
  esp8266.println(cmd);
  delay(wait);
  
  while (esp8266.available()) {
    Serial.write(esp8266.read());
  }
}

Join ESP8266 to WiFi.

1. Open Serial Monitor (9600 baud).
2. Watch for AT command responses.
3. ESP8266 should connect to your WiFi.
4. Note the IP address shown.
5. Test with AT command: AT+PING="google.com"

Communicate with a server.

1. Download TCP client app on smartphone.
2. Connect phone to same WiFi network.
3. In app, connect to ESP8266 IP address, port 80.
4. Send AT commands from phone.
5. Arduino receives and can respond to messages.
6. Example: send sensor data to phone or web server.

Put WiFi connectivity to use.

1. Ideas: WiFi temperature monitor, remote LED control, data logger.
2. Read sensor data on Arduino.
3. Send data via ESP8266 to phone or cloud service.
4. Control Arduino outputs remotely via WiFi commands.