The ESP8266 WiFi Module is a low-cost WiFi microchip that allows microcontrollers to connect to WiFi networks. It has an integrated TCP/IP stack, onboard processing power, and operates at 3.3V. It can connect to WiFi networks and make HTTP requests using simple AT commands. The ESP8266 comes in many modules that vary in available GPIO pins and firmware versions, which can impact the baud rate used to communicate with it from another device like an Arduino.

1. ESP8266
“Designed for the needs of an increasingly connected world”
Pavlos Isaris

2. Introduction
The ESP8266 WiFi Module is a self contained SOC (system on a chip) with integrated
TCP/IP protocol stack that can give any microcontroller access to a WiFi network.

3. Features
● Very low cost ( 3-5$ )
● Pre-programmed with an AT command set firmware
● Growing community
● Enough on-board processing power to deal with sensors
through GPIO
● Operating at 3.3V
● Can draw up to 170 mA of current
● Not breadboard-friendly :-(

4. Βreadboard friendly version (ESP-12)

6. Why do we need a Voltage regulator?
The ESP8266 may require more than the 35mA supplied by the Arduino 3.3V pin

7. Baud rate problem
The ESP-8266 comes in various firmware versions, varying also
in the operating baud rate (older operate at 115200 bauds).
My ESP8266 operates in 115200 bauds/second. This means that
we can only use hardware serial to communicate with it
(Arduino Software serial pins handle only 9600 bauds/second)
In such occasion, it is possible to use an Arduino MEGA (4x
Hardware serial couple-pins)

8. Alternative - Update firmware version
You can also use an FTDI adapter (like the FT232rl) or FTDI
cable, to communicate via USB with ESP8266
There are plenty of tutorials about how to update the firmware
version
After you have updated the firmware version you can change the
baud rate

9. Multiple variations

10. Module GPIO Notes
ESP-01 GPIO0/2/16 Most common module.
ESP-02 GPIO0/2/15
ESP-03 GPIO0/2/12/13/14/15/16 Most popular in esp8266.
com poll
ESP-04 GPIO0/2/12/13/14/15/16
ESP-05 None
ESP-06 GPIO0/2/12/13/14/15/16
ESP-07 GPIO0/2/4/5/12/13/14/15/16
ESP-08 GPIO0/2/12/13/14/15/16
ESP-09 GPIO0/2/12/13/14/15 1MB Flash memory
ESP-10 None
ESP-11 GPIO0/1

11. Using Arduino IDE Serial Monitor
#include <SoftwareSerial.h>
SoftwareSerial ESPserial(2, 3); // RX | TX
void setup()
{
Serial.begin(115200); // communication with the host computer
ESPserial.begin(115200);
Serial.println("");
Serial.println("Remember to to set Both NL & CR in the serial monitor.");
Serial.println("Ready");
Serial.println("");
}

12. Using Arduino IDE Serial Monitor
void loop()
{
// listen for communication from the ESP8266 and then write it to the serial monitor
if ( ESPserial.available() ) {
Serial.write( ESPserial.read() );
}
// listen for user input and send it to the ESP8266
if ( Serial.available()) {
ESPserial.write( Serial.read() );
}
}

13. Basic AT commands

14. Checking for available WiFi networks

15. Connect to Network

16. See details

17. Send a request
Allow multiple connections
Start connection
Specify bytes to be sent
In this case it is “GET /
HTTP/1.0rnrn”

18. Get the response back

19. Acting as TCP Server

20. Acting as a Wifi Access point

21. ESP8266 core-library
#include <Adafruit_ESP8266.h>
#include <SoftwareSerial.h>
#define ARD_RX_ESP_TX 2
#define ARD_TX_ESP_RX 3
#define ESP_RST 4
SoftwareSerial softser(ARD_RX_ESP_TX, ARD_TX_ESP_RX);
Adafruit_ESP8266 wifi(&softser, &Serial, ESP_RST);
#define ESP_SSID "SSIDNAME" // Your network name here
#define ESP_PASS "PASSWORD" // Your network password here
#define HOST "www.adafruit.com" // Host to contact
#define PAGE "/testwifi/index.html" // Web page to request
#define PORT 80 // 80 = HTTP default port

22. ESP8266 core-library
softser.begin(9600); // Soft serial connection to ESP8266
Serial.begin(57600); while(!Serial); // UART serial debug
wifi.connectToAP(F(ESP_SSID), F(ESP_PASS))
Serial.print(F("OKnRequesting page..."));
if(wifi.requestURL(F(PAGE))) {
Serial.println("OKnSearching for string...");
if(wifi.find(F("working"), true)) {
Serial.println(F("found!"));
} else {
Serial.println(F("not found."));
}
} else { // URL request failed
Serial.println(F("error"));
}
wifi.closeTCP();

23. Espert - Development board
http://www.espert.co/ (v2.0 To be released by April 2016.)