I've written an UI in HTML5 and JavaScript. I chose this implementation so that I could share the same code between both Android Chrome and Windows 8 RT.
Now, my next objective is to write data to a USB HID. The device that I'm communicating with is treated as an HID. I'm mentioning this part in case there's a way to write to an HID device rather than a USB RAW device.
I've done a lot of research on the matter. But, the HTML5 specs are changing so often that maybe I missed something.
Anyways, can someone suggest a language or implementation that I can use to share common code to access a USB device on Android and Windows 8 RT? If there isn't a way to share between the two, how about a suggestion to get USB communication only on Android?
Below is my research along with conclusions:
Silverlight: UNSUPPORTED. In terms of web plugin, not supported on Windows 8 RT or Android
Flash: Possible option. Supported in both operating systems, although they removed support for Android with release of Jelly Bean
HTML5: UNSUPPORTED
- Looked at the GamePad API, but it seems to only support reading from a gamepad
- Looked at Device tag, but this tag no longer exists in the current draft. I read that the "navigator" object replaces it in Javascript, but it seems completely different. Also, Device only targets acquiring video and audio
JavaScript: UNSUPPORTED. From my understanding, this is because it'd be a security risk.
Chrome Packaged App: UNSUPPORTED. Unsure about support in Windows 8 RT. But, it is not supported in Android Chrome, either.
- A USB API exists that accomplishes exactly what I need, but the API is only available to a packaged app
Java Applet: UNSUPPORTED. Unsure about support in Windows 8 RT. But, it is not supported in Android Chrome, either.
- Many resources available regarding how to communicate with USB devices. However, since java applets aren't supported on smartphones, this ends up being unsupported.
A couple of useful posts
I've actually thought about how to do things similar to this....
Here's is one way sure way to do it if you have control over the computer which has the usb device attached:
Have the computer with the USB device run a web server such as apache/php. Have it only listen to localhost.
Then in the html page being viewed, execute an ajax post to localhost/somescript.php (or cgi or cfm or whatever).
In php/cgi script communicate to the USB device and then return a json string to the browser saying something happened.
UPDATE:
Another approach is to use Custom URL Protocols. You create an executable and "install" it on the client computer along with your custom url protocol.
Then you can invoke the executable from the browser using your custom url protocol.
If the usb device you want to control is a barcode printer, you can use jZebra
https://code.google.com/p/jzebra/
This is an applet which directly communicates to locally connected printers.
There is one more alternative Web Socket.Create a web socket server which will access the usb device in local system.
Connect your web server using Web Socket from Web Application.Web Socket has standard Api
You can do something like this
var host = "wss://localhost:25000/test";
Websokcet ws = new WebSocket(host);
You can create your web sokcet Server using RFC 6455
for older browser you can think of http server as well.
Please have a look at JSFS. It works similar to Chris_vr's approach and is already a working solution.
https://github.com/jsfsproject/jsfs. It's free and licensed under GPL.
How about this?
Writing to a serial port:
var writeSerial=function(str) {
chrome.serial.write(connectionId, str2ab(str), onWrite);
}
// Convert string to ArrayBuffer
var str2ab=function(str) {
var buf=new ArrayBuffer(str.length);
var bufView=new Uint8Array(buf);
for (var i=0; i<str.length; i++) {
bufView[i]=str.charCodeAt(i);
}
return buf;
}
来源：https://stackoverflow.com/questions/15535409/write-data-to-usb-hid-using-javascript-html5-or-any-cross-platform-language-s