README

This is a small, sample project demonstrating how to use johnny-five (a Node library which lets you talk to many microcontoller platforms—including the Arduino and Tessel—via JavaScript) in conjunction with express (another Node library which lets you write a simple web server with JavaScript) to use the Arduino as a web server.

To run this project, we need to do two things:

1. Teach the Arduino how to receive communications from our computer for the johnny-five library.
2. And install the required libraries and run the code for this sample project.

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To do (1):

1. Download and install the Arduino IDE (integrated development environment—kind of like a Sublime Text which can talk to the Arduino)
2. Open the Arduino IDE, and open the StandardFermata example by going to File > Examples > Fermata > StandardFermata
3. Upload the StandardFermata sketch by selecting Sketch > Upload

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To do (2):

1. Clone this repository via GitHub Desktop or from the command line (git clone git@github.com:dgmd/johnny-five-express-sample.git).
2. Open the cloned repository in your terminal.
3. Within the repository, run npm install in your terminal. This uses npm—Node's package manager—to install the libraries required for this project (express and johnny-five) by looking within the package.json file.
4. Connect your Arduino to your computer via USB.
5. In your terminal (which should still be within the cloned repository), run node server.js
6. You should see Server's up at http://localhost:3000!; when you do, go to http://localhost:3000 and you should see "Hello from server.js!"
7. Now you can explore the other routes and behavior detailed in server.js

Suggested Explorations

Here are a few ways to play around with and explore the syntax and setup of using Express and the Arduino which might be interesting and useful to you if you're planning to build a project with a physical, web-connected component.

Exploration 1 — Add a route of your own

Get comfortable with the syntax for adding routes with Express and add your own which either returns a particular string, or perhaps serves up a different web from a file.

Exploration 2 — Add a route which returns something depending on a URL parameter

You can use the req.params object to access parameters passed in a URL—e.g. If someone goes to /hello/world and then /goodbye/world, you can write a route whose returned content depends on hello v. goodbye.

Exploration 3 — Add a route which returns something depending on the state of an individual pin

You can query the state of an individual pin using johnny-five's Pin API. Just as you can write a route which returns something different depending on the URL you go to, you can also write a route which returns something different depending on the state of an individual pin.

Exploration 4 — Add a route which serves a web page which regularly queries the state of a pin and changes something on the web page depending on that pin

The first three explorations are all a single interaction—a user goes to a URL and Express serves up a page after looking at the URL and/or the Arduino's pins. But you can also create a web page which itself regularly queries the server using XMLHTTPRequest. In this exploration, try to create a web page which is served up at a particular URL, but which when it loads, regularly queries (in JavaScript, via XMLHTTPRequest) a different URL (say, one which is measuring the state of a pin) and modifies the content of the page accordingly…e.g. You could have a web page where the background-color of a div changes when a particular pin is set low (say, by a switch).

Exploration 5 — Add a route which serves a web page which uses WebSockets to update the page in real time depending on the state of a pin

In Exploration 4, the web page is regularly asking the Arduino about the state of a pin. This is called polling. Ideally, our system could update itself only when something changes on the Arduino. To do that, we need easy, constant, two-way communication between our server and our web page. This is why the WebSockets technology was introduced. Socket.io is a convenient wrapper around the WebSockets protocol that makes talking WebSockets pretty simple.

In this exploration, try to recreate the results from Exploration 4, but this time using WebSocket's event-driven approach, instead.