How to make two ESP8266 communicate through WiFi with Espruino and JavaScript

In this article we will make two ESP8266 communicate using the WiFi network. We will use Espruino and some JavaScript code.

Setup the WiFi

Espruino offers a WiFi module that let us to connect to a WiFi network.

The code below will connect our ESP to the WiFi network and will print the information about the obtained IP plus other network information:

The result should be:

Please take note of the IP for both the devices, currently there are no other way to discover each other.

Now both the devices are connected to the WiFi network. Now we can make them talk each other. In this example we elect one board server and the other client. The client board will start a TCP communication toward the server board. Once connected they will able to exchange messages.

Setup the server

The server first setup the WiFi connection, then creates a socket server on port 1234 for receiving connection from the clients. When a connection is established it will print the messages coming from the client and will close the connection saying “I’m a server! Goodbye.”.

Setup the client

The client, after get ready with the WiFi connection, will try to connect to the server. When the connection is established it will send a “Hello I’m a client!” message and will wait for responses from the server.

The output

Here the output in the server side:

Here the output for the client side:

Reading pressure and temperature from a BMP085 using an ESP8266 board and Espruino

In this short tutorial we will read the barometric pressure from the BMP085 sensor using an ESP8266 board and Espruino with some Javascript code.

Wiring

Our BMP085 sensor communicates through an I2C connection, so we need to connect the SCL pin to the corresponding D1 pin and the SDA pin to the corresponding D2 pin in the ESP board. The other two pins are dedicated to the power.

Code

To read both pressure and temperature we will use the BMP085 module of Espruino. After the I2C connection is setup we initialize the BMP085 module, then we start polling and printing the sensor information.

Here the result:

Showing temperature in a OLED display using Espruino and an ESP8266 board

In this short article I will show you how to read the temperature and the relative humidity from a DHT22 sensor and display it in a 128×64 OLED display using an ESP8266 board with Espruino and JavaScript running on it.

Wiring

The DHT22 has 4 pins, only three used: two for the power and one for the data. We will connect the power pins to the corresponding pins on the ESP8266 board and the data pin to one of the GPIO pin, D7 in our schema.

The display is a SSD1306 with a resolution of 128×64 pixels and I2C communication. The display has four pins, two for the power and two for the I2C. We connect the I2C pin to the corresponding D1 e D2 pins in the ESP8266 board.

Code

Espruino provides a module for reading the temperature and the relative humidity from a DHT22 sensor. We will use it to read both the values from the connected sensor.

Then we will use the I2C module combined to the SSD1306 module to show the collected information in the display.

We will poll the sensor every 2 seconds and update the display consequently.

The final result:

How to install Espruino firmware in an ESP8266 board

espruino_logo

This is an update to the installation tutorial I’ve already wrote: Run JavaScript on your ESP8266 using Espruino firmware

For this installation I’m using a D1 mini board which is a “wrapper” for the ESP8266 (ESP-12) board.

Flash the Espruino firmware

The first step is to flash the Espruino firmware into the ESP board. You can find a tutorial in the Espruino site. In this article I’m putting a short list of instructions ready to use.

Install the ESP tools with the following command:

The ESP tools are a set of Python scripts necessary to flash a firmware in the ESP board.

We need now the last version of the Espruino firmware, you can get it from the download page of the Espruino site. The zip file will contain the Espruino firmware also for the ESP8266 board.

We are ready to flash our board. The following instruction are for a ESP-12 board connected to the /dev/ttyUSB0 port. Please refer to the original tutorial for a different version of the ESP board. First move to the folder where you have unzipped the firmware.

The blue led in the board will start blinking and you will see the following output in console:

If you’re having problems finding the correct device path in Linux:

  • first check that you’re using an USB data cable. The first time I’ve tried I was getting crazy because I was using a simple power USB cable.
  • second try this console command to print the system events when the USB cable is plugged:

    When you plug the cable you will get something like this:

Ready to run

After the flash operation the board is ready to receive your JavaScript commands!

To send the commands you need to connect to the board using a serial connection (through the USB port). Under linux you can use the screen program:

Now you can send JavaScript commands that will be interpreted and the output provided as response.

For example writing:

you will get:

You can call functions, for example:

it will reset the board and print a boot message:

If you want to exit from Screen press CTRL-A and then \.

Now you’re ready to write your JavaScript code and run it in a ESP8266 board, for example using the Espruino Web IDE.

 

Handling polymorphism with Jackson

Sometime you need to serialize a hierarchical model to JSON. Jackson offers different ways to handle the problem. Here I will expose two of them.

tl;dr;

First solution: Annotate the super class with @JsonTypeInfo(use=Id.CLASS)Pros: works with any subtype. Cons: breaks with classes or package renaming.

Second solution: Annotate the super class with:

adding a JsonSubTypes.Type for each sub-class. Pros: no problems with renaming if custom names are provided. Cons: requires to specify all the sub-classes in the super-class.

Long story

We have animals:

between them dogs:

and cats:

We try to serialize a cat:

obtaining the following JSON:

But when we try to deserialize it:

we get an exception:

Not good. Looks like Jackson is not able to understand if the JSON refers to a cat or to a dog.

We can help Jackson annotating the super-class with the JsonTypeInfo annotation. The annotation will add type information to the generated JSON.

We can tell Jackson to use the fully-qualified Java class name as type information:

a @class property will be added with the full class name:

If you like a shorter class name you can use the Id.MINIMAL_CLASS option:

a @c property will be added with a shorter class name:

With both solutions we should be worried about refactoring: if we change the classes or package names we will not be able to deserialized previously stored JSON.

As alternative we can store custom names using the Id.NAME option:

Obtaining a JSON with a new property @type with the type name:

By default Jackson uses the class name as name.

Unfortunately during the deserialization we get an exception:

Jackson is not able to map the type name to a class. To solve the problem we provide sub-class information with the JsonSubTypes annotation:

We can use custom names specifying them in the Type annotation:

Now we get a JSON with our custom names:

We can obtain the same result annotating the sub-class with a JsonTypeName annotation:

With custom names we can refactoring without problems but we will need to specify all the subtypes in the super class.

For more information please refer to official documentation: http://wiki.fasterxml.com/JacksonPolymorphicDeserialization

Run JavaScript on your ESP8266 using Espruino firmware

espruino_logo

Espruino is a board that comes with a pre-installed firmware capable of running JavaScript code. You can buy one of the official board or you can flash a list of “not officially supported” boards. The list contains also the ESP8266 board, so let’s try to run our JavaScript code on it.

For this article I’m using a NodeMCU Amica board which lets us play with the ESP8266 (ESP-12) without the burden of connecting it to the computer and also powering it to the right voltage all from a micro USB port.

All the programs in the article are run from a Linux Mint 17 operative system.

Flash the firmware on ESP8266

First step is to flash the Espruino firmware into the ESP board. You can find a tutorial in the Espruino site. In this article I’m putting a short list of instructions ready to use.

Create a working folder and download there the ESP tools.

The ESP tools are a set of Python scripts necessary to flash a firmware in the ESP board.

We need now a ESP8266 dedicate version of the Espruino firmware. You can find the latest version in this forum post. Here the instructions to download the last version available today (26/06/2016):

We are ready to flash our board. The following instruction are for a ESP-12 board connected to the /dev/ttyUSB0 port. Please refer to the original tutorial for a different version of the ESP board.

The blue led in the board will start blinking and you will see the following output in console:

(Did you noticed the “Running Cesanta flasher stub…” print? Looks familiar?)

If you’re having problems finding the correct device path in Linux:

  • first check that you’re using an USB data cable. The first time I’ve tried I was getting crazy because I was using a simple power USB cable.
  • second try this console command to print the system events when the USB cable is plugged:

    When you plug the cable you will get something like this:

After the flash operation the board is ready to receive your JavaScript commands!

To send the commands you need to connect to the board using a serial connection (through the USB port). Under linux you can use the screen program:

Now you can send JavaScript commands that will be interpreted and the output provided as response.

For example writing:

you will get:

You can call functions, for example:

it will reset the board and print a boot message:

Time to use the Espruino Web IDE.

Espruino Web IDE

The Espruino project provides a Web IDE for editing and uploading your JavaScript code to your board. The IDE also manages the modules that can be used in your code in order to extend the basic functionalities offered by the SDK, for example to use the Wi-Fi device or external sensors like the DHT-22.

The Web IDE can be installed as Chrome application or as NodeJS package.

Espruino Web IDE

After the IDE has been installed we have to configure the baud rate in order to have the communication with the board working fine. Click on the gear icon on the top right, select the COMMUNICATIONS tab, then set the “Baud Rate” to 115200.

espruino_web_ide_settings

Now everything is ready to play. Click the connect button on the top left, select the USB port to use and the IDE will connect to the board.

On the left side you can write commands directly to the board and get the response live.

espruino_web_ide_console

On the right side you can write your code and then upload it to the board using the upload button on the center.

espruino_web_ide_editor

Now we ready to write our first JavaScript program to run on our ESP8266 board!

Run JavaScript in your ESP8266 device

In the previous article we saw how to build the Smart.js framework and flash the firmware in the ESP8266 device. Now is time to play a little more with it.

In this article I will show how to read the temperature and the humidity from a DHT11 sensor connected to the ESP8266 device and how to send those values to a public site using an HTTP GET request, all using JavaScript code.

How to add new files to the firmware

To add a new file to the firmware add it in the smart.js/platforms/esp8266/fs folder. All the files in the fs folder are added to the file system of the firmware during the build process. Those file will be accessible using the File API.

Lets try it creating a file myfirst.js with the following code:

Now save the file and run the firmware build process:

Connect the ESP device as explained before and flash the new firmware.

In the console we can now load and evaluate our JavaScript file using the eval function from the File API:

The code in the file is evaluated and the functions that we have defined can now be called:

The sayHello method prints the “Hello World” message visible in the output area. Instead the “undefined” value is the value returned by the function and printed by default.
Let’s try the other function getMyIp:

The execution terminates with an error message, this happens because the WiFi is not configured. We can configure it using the Wifi API:

The setup function will make the ESP device scan for the specified network and connect to it. If everything go fine the method return the true value.

The Wifi API offers also a method to check the current Wifi status:

Now that the Wifi is configured we can try the getMyIpFunction:

The printed IP is our external IP, the one of our modem. If, instead, we want the internal IP, the one assigned by our access point, simply call Wifi.ip().
Now we are able to write our program and execute it. Time to read values from a DHT11 sensor.

Wiring the DHT11

To read the sensor values we will use the only available pin in the ESP device the GPIO_02.
First connect the VCC and GND pins of the sensor to the respective VCC and GND on the USB adapter. Then connect the DATA pin to the ESP GPIO_02 pin. Note that the GPIO_0 is NOT connected to the GND.

Now connect the USB adapter to the computer and click the “connect” button on the Flash’n’Chips tool. I don’t know why but sometime I have to disconnect the sensor DATA pin before turn on the ESP device otherwise the ESP console don’t reply.

The framework comes with the support for the DHT11 sensor, a global object DHT11 is defined with a read function. The function takes an integer as input, the sensor port, in our case is the number 2.

We can use the DHT11 object simply calling his read method:

The returned value is an object with temperature and relative humidity. Time to publish the sensor values.

Publish the sensor values

We will publish the sensor values in a site that accepts a GET request with the values as url parameters, something like http://mysite.com/publish.php?temperature=22.0&humidity=55.0

Create a sensor.js file in the fs folder with the following code:

Build the firmware with the new file. Before flash the device re-connect the GPIO_0 to the GND and disconnect the sensor DATA pin. After the flash is complete disconnect the adapter e disconnect the GPIO_0 from the GND.

Connect the adapter to the computer, then click the “connect” button in the Flash’n’Chips tool. After the console is connected re-connect the DATA pin.

First, setup the WiFi:

Then load and evaluate the sensor code:

We can now run our method readSensor. It will read the values from the sensor and publish them to a site using the HTTP API. Here the console output:

And a chart built using the published values:

chart

So our little ESP device is able to read values from a sensor and publish them in a site using the Wi-Fi network.

Continuous and automatic publication

What if we want a continuous publication of sensor values?
Here the solution:

This method will publish the sensor data every 5 seconds.

What if we want to start the publication automatically without the need to run it from a console?
Here the solution.

First append those lines to the sensor.js code:

The first line checks if the WiFi is active otherwise setups it. The second line starts the data streaming.

In order to make our sensor.js file evaluated at boot time we need to modify the user.js file under smart.js/src/js folder appending this line:

Build and flash the firmware. After rebooting the device it will start to publish the sensor values.

Conclusions

We saw how to run our JavaScript code in our ESP device thanks to the great work from Cesanta. The framework is still under development so the APIs or the tools can change in any moment.

I think there will be for sure a lot of news in the coming months. One thing will be the integration of the web server Mongoose in the Smart.js framework, that means connecting directly to the device using the browser!
Another thing, as I can understand from the Smart.js online dashboard, is that we will be able to upload our JavaScript code directly from our browser so we don’t need to flash the firmware every time we update the code!!!

Build the Smart.js framework

Cesanta has developed a JavaScript engine, capable of run JavaScript code in the ESP8266 device and in other embedded devices. The JavaScript engine is provided with the Smart.js framework. The framework offers a set of APIs for files management, networking and WiFi management, SPI and I2C communication, GPIOs and Cloud services. The framework is distributed ready to flash under Windows and Mac. Here you can find a short guide.

In this article I will show how to build the framework under the Ubuntu’s like OS and flash your ESP8266-01 device with the latest Smart.js framework version.

Framework build

In order to build the Smart.js framework we need first to install Docker. A complete and updated set of instructions on how to install Docker can be found here. To make it short you can simply run this command in the console:

After the Docker installation is complete we checkout the framework code:

To build the framework move to the esp platform directory:

and run the build process:

The first time it will require a little bit because the tool has to download the docker images. Next builds will be really fast.

The three binary files composing our ESP firmware will be generated under the firmware folder. Now we need the tool to flash the ESP device.

Flash’n’Chips build

The Smart.js framework is provided with a tool for flashing our devices: Flash’n’Chips.

fnc

To build the tool first we need to install the required dependencies: Qt 5 and libftdi.

To install Qt 5 you can use the installer distributed by Qt here. It will install all the Qt tools under the specified folder. In the folder you will find the binary required to compile Flash’n’Chips. I suggest to add the bin folder to your PATH variable:

To install the libftdi library run:

Now we are ready to compile the Flash’n’Chips tool. Move to the source folder:

And run first:

then:

In a bit the tool will be ready to be executed. Time to connect the ESP device to your computer.

Wiring

To connect my ESP 8266-01 I’m using a FT232 adapter. If you are using it remember to set it to 3v3.

ft232

We connect the respective VCC and GND pins, same for RX and TX pins but inverting them. We need also to connect the ESP CH_PD to the VCC and, only for the flashing process, the ESP GPIO_0 to the GND.

ft232 esp8266_bb

We are now ready to flash the previously built firmware into the ESP device.

Flash the ESP

Connect the USB adapter and run the Flash’n’Chips tool using this command from the flashnchips folder (I had to use this parameters for some issues with my ESP board):

The tool should show the “Flash firmware” button active.

fnc ready

If not press the “Detect devices” button and see if the adapter is recognized.

Press the “Flash firmware” button and the flash process will start. You can see the progress bar running and the current operation explained under it.

fnc flash

When the process is completed the communication console will be activated under the progress bar area. You will see some messages from the device.

fnc console

Now we are ready to run some JavaScript commands in our ESP device.

Play with console

The Flash’n’Chips console has two areas, the first shows the device output, the second let us write commands to send to the device. The commands are snippets of JavaScript code that are executed on the device.

We can start writing a simple expression:

The device will calculate it and reply with the result:

We can also use the framework’s APIs, for example we can list the files present on the device:

It should output something like:

These are some of the JavaScript functions that our device can run. In the next article we will see how to run a simple program that reads values from a DHT11 sensor and publish them in a site.

How to translate a search query into a JavaScript filtering function

In a project I had to translate a search query into a filtering function to apply to a stream of JavaScript objects. The query language was very simple, boolean expressions of property constraints, for example “name:john AND age:52” where the search should return all the objects with property “name” equals to “john” and property “age” equals to 52.

The first step was to parse the search query with a parser. You can write a parser by hand or your can use a parser generator like PEG.js. I prefered the second one.

With the online editor I’ve wrote the language grammar:

The generated parser takes as input the text to parse and returns the parsed elements:

The grammar can be changed to make the parser method return a boolean expression:

The parser for a query like “name:john AND age:52” generates the following expression:

In the generated expression I’ve used an utility method that checks if the specified couple of name and value exists as property for the specified object:

The expression can be then passed as parameter in the function constructor:

Now you can use the new function as filter, for example with stream.js streams:

The grammar can be expanded with more operators and capabilities.