Nuts and Volts - October 2015

characters which must be edited into the TeleduinoClient sketch along with your Wi-Fi network’s SSID and password before downloading into the ESP8266. The API key must also be used in all API calls from your browser.

Once the sketch is downloaded into the ESP8266, it will first make a connection to your Wi-Fi network and then it will open a TCP connection to the Teleduino server. Once this connection is made, the ESP8266 will authenticate itself to the server by providing the API key. If you bring up the serial monitor, you will be able to watch this interaction take place.

If all goes well, the Teleduino server will begin sending ping messages to the ESP8266 about every five seconds. Because the ESP8266 establishes an outgoing connection to the Teleduino server, there is no need to open any ports in your firewall and thus create any new security concerns for your network.

To summarize: Once the TeleduinoClient is configured, it automatically connects itself to the Teleduino server when powered up. The Teleduino server translates instructions received over the Internet into actions on the Teleduino device which (in this case) is the ESP8266.

As mentioned, I ported only a (very small) subset of Teleduino functionality. In fact, the TeleduinoClient sketch only recognizes a setDigitalOutput API call, but that is enough to prove the concept workable. On the second prototype shown in Photo 5, I have connected an LED to the ESP8266's GPIO2 pin through a 1K ohm resistor to ground. If I go to my browser and type in (this rather long URL) https://us01.proxy. teleduino.org/api/1.0/328.php?k=<YOUR KEY GOES HERE> &r=setDigitalOutput&pin= 2&output=1&expire_time=0&save=0, the LED will turn on. If I try this again but change output=0, the LED will turn off.

Keep in mind that for this demo, the ESP8266 is turning an LED off and on by way of commands entered into a browser which can be located anywhere in the world. If instead of an LED connected to the ESP8266 you connected a solid-state relay (SSR), you could control devices such as a light, a heater, an alarm system, etc. The possibilities are endless.

Want to control your Teleduino device from your Android smartphone or tablet? Check out apps like Teleduino Controller Pro V2 in the Google Play store.

Conclusion

This article doesn't begin to describe the cool things that can be done using the ESP8266. I hope after reading this article you will come up with many ideas for your own projects. I have a few in mind that I may share in future articles if there is enough interest. Please let Nuts & Volts know if you would like other articles about using the ESP8266.

Devices like the ESP8266 make possible the idea of connecting almost anything to the Internet and controlling and/or monitoring them from anywhere in the world. The ESP8266 is a giant step forward in the Internet of Things (Io T) revolution. NV

October 2015 47

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Resources

The following links provide further information about ESP8266 devices: Information about the ESP8266 Arduino port can be found at https://github.com/esp8266/ Arduino.