ESP8266 Thing Hookup Guide

Contributors: jimblom
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Example Sketch: AP Web Server

Not only can the ESP8266 connect to a WiFi network and interact with the Internet, but it can also set up a network of its own, allowing other devices to connect directly to it. This example demonstrates how to turn the ESP8266 into an access point (AP), and serve up web pages to any connected client.

Copy and paste the code from below, or download it here.

#include <ESP8266WiFi.h>

// WiFi Definitions //
const char WiFiAPPSK[] = "sparkfun";

// Pin Definitions //
const int LED_PIN = 5; // Thing's onboard, green LED
const int ANALOG_PIN = A0; // The only analog pin on the Thing
const int DIGITAL_PIN = 12; // Digital pin to be read

WiFiServer server(80);

void setup() 

void loop() 
  // Check if a client has connected
  WiFiClient client = server.available();
  if (!client) {

  // Read the first line of the request
  String req = client.readStringUntil('\r');

  // Match the request
  int val = -1; // We'll use 'val' to keep track of both the
                // request type (read/set) and value if set.
  if (req.indexOf("/led/0") != -1)
    val = 0; // Will write LED low
  else if (req.indexOf("/led/1") != -1)
    val = 1; // Will write LED high
  else if (req.indexOf("/read") != -1)
    val = -2; // Will print pin reads
  // Otherwise request will be invalid. We'll say as much in HTML

  // Set GPIO5 according to the request
  if (val >= 0)
    digitalWrite(LED_PIN, val);


  // Prepare the response. Start with the common header:
  String s = "HTTP/1.1 200 OK\r\n";
  s += "Content-Type: text/html\r\n\r\n";
  s += "<!DOCTYPE HTML>\r\n<html>\r\n";
  // If we're setting the LED, print out a message saying we did
  if (val >= 0)
    s += "LED is now ";
    s += (val)?"on":"off";
  else if (val == -2)
  { // If we're reading pins, print out those values:
    s += "Analog Pin = ";
    s += String(analogRead(ANALOG_PIN));
    s += "<br>"; // Go to the next line.
    s += "Digital Pin 12 = ";
    s += String(digitalRead(DIGITAL_PIN));
    s += "Invalid Request.<br> Try /led/1, /led/0, or /read.";
  s += "</html>\n";

  // Send the response to the client
  Serial.println("Client disonnected");

  // The client will actually be disconnected 
  // when the function returns and 'client' object is detroyed

void setupWiFi()

  // Do a little work to get a unique-ish name. Append the
  // last two bytes of the MAC (HEX'd) to "Thing-":
  uint8_t mac[WL_MAC_ADDR_LENGTH];
  String macID = String(mac[WL_MAC_ADDR_LENGTH - 2], HEX) +
                 String(mac[WL_MAC_ADDR_LENGTH - 1], HEX);
  String AP_NameString = "ESP8266 Thing " + macID;

  char AP_NameChar[AP_NameString.length() + 1];
  memset(AP_NameChar, 0, AP_NameString.length() + 1);

  for (int i=0; i<AP_NameString.length(); i++)
    AP_NameChar[i] = AP_NameString.charAt(i);

  WiFi.softAP(AP_NameChar, WiFiAPPSK);

void initHardware()
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);
  // Don't need to set ANALOG_PIN as input, 
  // that's all it can be.

After uploading this sketch, find another device that you can connect to a WiFi network -- phone, laptop, etc. Look for a network called "Thing-XXXX", where XXXX is the last 2 bytes of the Thing's MAC address.

Connecting to the Thing AP

The sketch sets the network's password to "sparkfun".

After connecting to your Thing's AP network, load up a browser and point it to The Thing should serve up a web page showing you its ADC and digital pin 12 readings:

The Thing serving up a web page

After that, give and a try, and keep an eye on the Thing's green LED while you do.

As always, check through the code comments to get a line-by-line breakdown of what's going on.