Arduino & ESP8266 Webserver

Update: This is a very old guide and there are much better examples available. If I were to to this again I would use one of the ESP8266 libraries that simplify the whole process. Libraries are available from the following links:
WiFi (ESP8266WiFi library)

Here is my first attempt at a web server using the ESP8266. It includes a request count and also a text input field.

ESP8266 webpage

Enter your name and hit submit

ESP8266 webpage 2

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FTDI + ESP8266

Just started to play with the ESP8266-01 modules. Purchased from Taobao.
These, I believe, are version 2 and have the LEDs near the antenna. When first started they identify themselves as [ Version:] and are version 018000902-AI03. This is a custom firmware from ai-thinker.

There seems to be quite a few different versions of similar modules. And the same module could have one of several firmwares.

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Arduino with HC-05 (ZS-040) Bluetooth module – AT MODE

Updated 19.07.2015
Updated 26.07.2015
Updated 30.10.2015

Update 2016-08-01
The zs-040 breakout boards are now being used for many different modules and you may not have the exact same boards as those shown below. Recently I received some new zs-040 HC06s and HC-05s that have a slightly different daughter board and a very different firmware. On the new HC-05s pin34 has to be pulled HIGH before connecting power to enter AT mode. Bringing pin 34 HIGH after powering the modules has no effect.


AT mode allows you to interrogate the BT module and to change some of the settings; things like the name, the baud rate, whether or not it operates in slave mode or master mode. When used as a master device AT commands allow you to connect to other Bluetooth slave devices.

There are many slightly different HC-05 modules, the modules I have are marked ZS-040 and have an EN pin rather than a KEY pin. They also have a small button switch just above the EN pin. They are based on the EGBT-045MS Bluetooth module.

Update: I now also have boards marked fc-114. See:
HC-05 FC-114 and HC-06 FC-114. First Look
HC-05 FC-114 and HC-06 FC-114. Part 2 – Basic AT commands
HC-05 FC-114 and HC-06 FC-114. Part 3 – Master Mode and Auto Connect

On the zs-040 modules there are 2 AT modes. I do not know if this is intentional but some commands only work when pin34 is HIGH. Other commands work when pin 34 is either HIGH or LOW. This fooled me for quite a while. For this post I have called the different modes “mini” AT mode and “full” AT mode.

HC-05 zs-040

To activate AT mode on the HC-05 zs-040 modules we can:
– 1. Hold the small button switch closed while powering on the module.
– 2. Set pin 34 HIGH (3.3v) when power on.
– 3. Close the small push button switch after the HC-05 is powered.
– 4. Pull pin 34 HIGH after powering the HC-05.

Method 1.
Enters AT mode with the built in AT mode baud rate of 38400. The baud rate cannot be changed by the user.
This method allows the module to enter AT mode on start but but does not keep pin 34 HIGH and uses the “mini” AT mode.

Method 2.
Enters AT mode with the built in AT mode baud rate of 38400. The baud rate cannot be changed by the user.
If you keep pin 34 HIGH you will enable the “full” AT mode which allows all AT commands to be used.
If you let pin 34 return LOW after power on then “mini” AT mode will be enabled.

Method 3.*
Enters “mini” AT mode using the user defined communication mode baud rate.

Method 4.*
Enters “full” AT mode using the user defined communication mode baud rate.

If pin 34 is kept HIGH then the HC-05 enters the “full” AT mode. If pin 34 is brought HIGH and returned to LOW it will put the module in to “mini” AT mode.

* added 21.07.2015

Method 1 and 2 are good in that you know the baud rate – it will always be 38400. This could be useful if you have modules other people have used or if you forget what communication mode baud rate you have previously set.

Method 3 and 4 adds convenience. You can enter AT mode, make changes and return back to communication mode without switching sketches and messing around with different baud rates.

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Turning a LED on and off with an Arduino, Bluetooth and Android. Part II: 2 way control

In the first part I showed how to control a single LED from an app created in App Inventor. This worked OK but was very limited. You could control only 1 LED and the control was one way; from the app to the Arduino. What if you want to have 2 way control of the LED and to be able to also control the LED from the Arduino side? What if you want to control more than 1 LED?

In this guide we look at adding two-way communication. Here we control an LED but you could have it doing anything.

Arduino-AI2-Bluetooth_1LED_01In first example you could only control the LED from the Android app, here we extend the example so that we can also control the LED at the Arduino side. When the LED is turned on or off by the Arduino we want the button in the app to update to show the correct LED status.

The first example used methods only suitable for controlling one LED, this time we will try to make it so the Arduino sketch and also the AI2 app can be easily scaled and so once you have the basic app in place adding extra buttons and controls should be fairly straight forward.

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Arduino / ATmega 328P fuse settings

Part of programming stand-alone ATmega chips is setting the fuse bytes, these are special settings that can be used to change how the ATmega chips operate.

Some of the things you can do by changing the value of the fuses include;

  • select different clock sources and change how fast the chip runs,
  • set the minimum voltage required before the chip works.
  • set whether or not a boot loader is used,
  • set how much memory is allocated to the boot loader,
  • disable reset.
  • disable serial programming
  • stop eeprom data being erased when uploading a new sketch.

There are many articles online but I could not find a single source that brought all the information together and fully explain what the fuses actually do.

It is important to remember that some of the fuse bits can be used to lock certain aspects of the chip and can potentially brick it (make it unusable). However, with a bit of care it is fairly straight forward to understand and use the fuse settings.

Disclaimer, I am relatively new to programming fuses and these are notes I wrote to help me remember things. The information is based on the data sheet for the ATmega chip, internet searches, and questions I asked on forums (especially the Arduino forum).

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Controlling a Solenoid Valve from an Arduino

Using the Arduino to control the solenoid valve is simply a case of setting a pin high for the appropriate amount of time. There is, however, a caveat, the solenoid works at a different voltage to the Arduino and you cannot directly connect the two. In this case a TIP120 transistor is used as a bridge.


The TIP120 allows a small dc voltage (from the Arduino) to switch a larger dc voltage (12V to the solenoid). It can be thought of as a switch, applying a current to  B allows current to flow between C to E.

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