Arduino/Wifi

Arduino Plus Wifi

I bought a couple of 8-pin wifi boards (ESP8266) to connect with an Arduino board to add wifi to some Arduino projects. Here's a photo of one of the chips:

ESP8266 Chip

The ESP8266 chip is a serial-over-wifi chip. (Whatever that means.)

These are actually pretty nifty chips, much more nifty than I originally thought: you can hook up a GPIO to the chip, and have it act as a standalone chip running an application on its own.

From their page: "Our ESP8266 Wifi Module is a low-cost and easy-to-use alternative to expensive wifi shields. This module is built around a powerful onboard microprocessor that features a built-in TCP/IP stack which handles all of the heavy lifting - leaving your Arduino free to communicate using simple serial and AT commands."

Serial Interface

This chip has 8 pins on the board. They are not labeled clearly. To interface with this chip (from an Arduino or a Raspberry Pi or a computer), you can use a serial connection.

A serial connection typically consists of four pins:

• VIN: voltage in (3.3 V or 5 V)
• GND: ground pin
• RX: receive channel
• TX: transmit channel

Note that the receive and transmit pins are crossed when connecting two devices.

Serial Hardware

You will need some hardware to talk to the wifi chip to program it. A serial interface capable of generating 3.3 V logic signals is necessary. A separate power source for this wireless chip is also critical to ensure that the chip can draw the full 300 mA it requires.

One nice advantage of a USB-to-RS-232 serial interface is that the power source comes from another device. WHile you can only interface with this wifi chip via a computer, this is kind of the point of serial.

Linkz

Documentation

Documentation for this product from manufacturer: http://www.vetco.net/catalog/product_info.php?products_id=16958

Information about interfacing with the chip via serial: http://www.seeedstudio.com/wiki/WiFi_Serial_Transceiver_Module

Manufacturer Expressif provides a nice set of pages with info and project ideas: http://bbs.espressif.com/

github library: https://github.com/willdurand/EspWiFi/blob/master/EspWiFi.h

esp8266 wiki: http://www.esp8266.com/wiki/doku.php?id=getting-started-with-the-esp8266

Hardware

Bi-directional logic converter: 3.3V to 5V (very cheap): https://www.sparkfun.com/products/12009

3.3V to 5V analog how-to, guide, tips and tricks: http://www.newark.com/pdfs/techarticles/microchip/3_3vto5vAnalogTipsnTricksBrchr.pdf

usb-to-serial TTL usb converter hardware: https://www.adafruit.com/products/954

usb-to-serial TTL usb converter guide: http://villagescience.org/running-raspberry-pi-usb-serial-ttl-adapter/

sparkfun version of the esp8266 (more pins?): https://learn.sparkfun.com/tutorials/esp8266-thing-hookup-guide/hardware-overview

another version with more pins: http://reflowster.com/blog/2015/05/11/esp8266.html

almost exactly the same hardware, using a serial-to-TTL converter: http://williamdurand.fr/2015/03/17/playing-with-a-esp8266-wifi-module/

Useful Code

This page [1] works by connecting an output signal from the Arduino to a USB-TTL serial converter chip. This signal is then sent back to the Arduino. The signal is (presumably) routed around to the Arudino's TX pin, and the Arduino's TX pin is hooked up to the Wifi chip's RX pin. Similarly, the Arduino's RX pin is hooked up to the Wifi chip's TX pin. This way, serial signals are routed through the USB-TTL converter.

   #include <SoftwareSerial.h>
   #define SSID "xxxxxxxx"
   #define PASS "xxxxxxxx"
   #define DST_IP "220.181.111.85" //baidu.com
   SoftwareSerial dbgSerial(10, 11); // RX, TX


   void setup()
   {
     // Open serial communications and wait for port to open:
     Serial.begin(57600);
     Serial.setTimeout(5000);
     dbgSerial.begin(9600); //can't be faster than 19200 for softserial
     dbgSerial.println("ESP8266 Demo");
     //test if the module is ready
     Serial.println("AT+RST");
     delay(1000);
     if(Serial.find("ready"))
     {
       dbgSerial.println("Module is ready");
     }
     else
     {
       dbgSerial.println("Module have no response.");
       while(1);
     }
     delay(1000);
     //connect to the wifi
     boolean connected=false;
     for(int i=0;i<5;i++)
     {
       if(connectWiFi())
       {
         connected = true;
         break;
       }
     }
     if (!connected){while(1);}
     delay(5000);
     //print the ip addr
     /*Serial.println("AT+CIFSR");
     dbgSerial.println("ip address:");
     while (Serial.available())
     dbgSerial.write(Serial.read());*/
     //set the single connection mode
     Serial.println("AT+CIPMUX=0");
   }


   void loop()
   {
     String cmd = "AT+CIPSTART=\"TCP\",\"";
     cmd += DST_IP;
     cmd += "\",80";
     Serial.println(cmd);
     dbgSerial.println(cmd);
     if(Serial.find("Error")) return;
     cmd = "GET / HTTP/1.0\r\n\r\n";
     Serial.print("AT+CIPSEND=");
     Serial.println(cmd.length());
     if(Serial.find(">"))
     {
       dbgSerial.print(">");
       }else
       {
         Serial.println("AT+CIPCLOSE");
         dbgSerial.println("connect timeout");
         delay(1000);
         return;
       }
       Serial.print(cmd);
       delay(2000);
       //Serial.find("+IPD");
       while (Serial.available())
       {
         char c = Serial.read();
         dbgSerial.write(c);
         if(c=='\r') dbgSerial.print('\n');
       }
       dbgSerial.println("====");
       delay(1000);
     }
     boolean connectWiFi()
     {
       Serial.println("AT+CWMODE=1");
       String cmd="AT+CWJAP=\"";
       cmd+=SSID;
       cmd+="\",\"";
       cmd+=PASS;
       cmd+="\"";
       dbgSerial.println(cmd);
       Serial.println(cmd);
       delay(2000);
       if(Serial.find("OK"))
       {
         dbgSerial.println("OK, Connected to WiFi.");
         return true;
         }else
         {
           dbgSerial.println("Can not connect to the WiFi.");
           return false;
         }
       }

Arduino Wifi Project

Project is to hook up a tiny LCD to the tiny wifi chip and make a tiny wifi monitor.

Add this to the Defcon badge, which should have a microchip that is programmable via serial as well, and could be wired up to control the LCD and tiny wifi chip.

Or, just hook it up to the battery or source of power, and have it standalone, running by itself.

Inspiration: http://www.seeedstudio.com/wiki/WiFi_Serial_Transceiver_Module

LCD Hardware:

• $15 tiny LCD, 128x128, 4D systems
  • 4d product page: http://www.4dsystems.com.au/product/4DLCD_144/
  • mouser: http://www.mouser.com/ProductDetail/4D-Systems/4DLCD-144/?qs=sGAEpiMZZMvrfGaWNM8PuULhtzAtzIIul0nv3rkl5n4%3d
• round LCD (too expensive)
  • mouser: round LCDs http://www.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=166384143
• Large enough to be useful - https://www.adafruit.com/products/1770
  • 2.8 inch display large enough for tiny drawings, would be perfect.

USB-Serial Converter:

• USB to serial converter:
  • FTDI provides a usb-serial adapter with a jumper to set the voltage level at 3.3 or 5, depending on what you wanna do:
  • inspired by this project/page: http://williamdurand.fr/2015/03/17/playing-with-a-esp8266-wifi-module/
• USB to serial converter, other options:
  • uart sbee povides BEE connections, like the usb-to-serial BEE boards that I have for the XBees, but these also have 4-pin serial header: http://www.seeedstudio.com/wiki/UartSBee_V4

Once you have all those pieces, this page becomes much more useful, and tells you what serial commands to actually run:

• http://www.esp8266.com/wiki/doku.php?id=getting-started-with-the-esp8266

What about the final - logic control from Arduino, USB adapter from 5 V to 3.3 V level, etc.?