Input and Output to Physical Devices from JavaScript

The JavaScript interpreter in most browsers is very isolated from the PC for security reasons. However, that is getting better:

• USB: Chrome, including on Android, now allows direct access to the USB ports via WebUSB. User permission is required. See "Can I Use*"
• Camera: Most browsers allow access to the camer, enabling things like Browser Based Image Processing: Subtraction, Area Sum
• Audio: You generate sounds and use that to control things e.g. Servo Motor control via <audio> or .Wav file
• Images: Of course, you control the screen so you can do things like Unidirectional I2C (2 wire) via Images

And those limitations can be removed or avoided by installing extra software into the computer. This can be a somewhat automated process where the user simply approves the installation and it is downloaded and installed. Security is only circumvented with the express approval of the user.

There are two basic means of doing this:

• Plug-ins: Software installed into the browser and system which allows direct communication between the JavaScript engine in the browser and the port. There are commercial Active-X controls for Internet Explorer and Java programs for other browsers. (see below)
• Services: A separate web listening service (like a web server) installed on the PC with the serial port, with which the JavaScript can communicate via TCP/IP. This service then translates between TCP/IP and the serial port.

Or you can avoid the browser issue by running outside the browser:

• http://phonegap.com/ Actually converts web apps into native phone apps. Allows access to some phone hardware such as geolocation, accelerometers, and compass.
• Although it is NOT actually HTML5 app development, DroidScript: JavaScript Language App does allow a lot of the same features and full access to phone hardware.
• Dexter Development Environment (DDE) https://github.com/cfry/dde allows JavaScript development in an Electron Application:

Introduction to Automation: Living beyond yourself.
Web pages, HTML, Javascript and the Internet Of Things (IOT)
(A Google drive collaborative presentation)

See also:

• https://girliemac.com/presentation-slides/html5-mobile-approach/deviceAPIs.html Access to device hardware from html5 mobile apps.
• https://www.html5rocks.com/en/tutorials/getusermedia/intro/ Accessing the cellphone or web camera and audio from the browser.
• https://developers.google.com/web/updates/2016/03/access-usb-devices-on-the-web Chrome, including on Android, now allows direct access to the USB ports via WebUSB. User permission is required. See "Can I Use*"
• http://chilipeppr.com/tinyg Sends gcode data from the web app to TinyG based CNC controllers via:
  https://github.com/johnlauer/serial-port-json-server
• http://log.liminastudio.com/itp/physical-computing/using-the-rn-xv-wifi-module-as-a-remote-switch Web addressable wi-fi connected device
• http://www.codeproject.com/Articles/389676/Arduino-and-the-Web-using-NodeJS-and-SerialPort2 A rather convoluted but no less useful method is to run a seperate service like Node.JS from nodejs.org as a web server on a PC (can be the same PC) and then use it's SerialPort and Sockets modules to connect to an Arduino (via the USB serial com port already connected to program the Arduino) and to the JavaScript in the web browser (via an unused http port). The Node.JS code could be moved out onto an embedded device or a dedicated PC server.
• http://docs.oracle.com/cd/E17802_01/products/products/javacomm/reference/api/javax/comm/SerialPort.html Java provides an interface to the serial port and other devices. This link will probably break when the next version of Java is released. Search their site for "JavaComm" to find it again.
  It may take extra work to get this going under Linux:
  http://www.agaveblue.org/howtos/Comm_How-To.shtml James Newton of MassMind replies:
  • http://www.walking-productions.com/jsserial/new/JSSerial.html This page documents using Java to provide access to the com ports from a web page. It depends on the RTXT library from
    http://rxtx.qbang.org/wiki/index.php/Main_Page and a signed java package from the author. Note, the web page will ask you to download and install Java if you don't have it, and will not allow you to see the content of the page until you do. Accessing the page via the web archive avoids this.

• http://www.activexperts.com/serial-port-component/howto/html/ Active-X control for serial port access in Microsoft Windows applications. Closed source, $295
• http://stackoverflow.com/questions/592099/javascript-interface-with-rs-232-serial-port/ Several options are discussed.
• http://strokescribe.com/en/serial-port-about.html Active-X control for serial port access in Microsoft Windows applications. Allows Excel, Internet Explorer, etc... to access a serial port and send or receive data. Closed source, $7.00.+
• https://academo.org/demos/virtual-oscilloscope/ A very nice little browser based o'scope with the sound card as audio input.

HTML5 Web Apps.