hack Archives - MAD Blog

You are doomed if your laptop has only one HDMI Port & you are running Linux in that box.

Unlike windows – where there are tons of easy to run solution, & there are still tons of solutions if you have big numbers in your pocket.

Certainly – I neither wish to spend money on external VGA/HDMI extender or docking station nor to change OS. So after googling a lot I discovered a solution which utilized a different machine to act as the streaming client. You can use RPI or an old p4 machine.

Below is how it works.

Adds a virtual display on your machine, usually all graphics card support at least one virtual display. You do all this using xrandr
Create a VNC Server to stream that display – but since you cannot each time run two commands just to connect display – we are running VNCViewer in listen mode
Connect to vnc viewer & keep running it in the background.

You Laptop —[Display Data]—> Network —-> VNCViewer

As suggested above you data is being streamed over the network – you cannot run 4k data. But if you have good Lan speed you won’t face any problem.

I have also optimized settings for best experience – so far I can use terminal, watch videos – the only drawback is you feel the lag when you use keyboard or mouse for realtime feedback.

In Client Machine, i.e. your laptop.

You will need to install x11vnc & screen

#!/bin/bash
#Run VNC server in remote device. 10.0.0.2 is my machine which has monitor connected.
ssh  root@10.0.0.2 "nohup /root/vncserver.sh > /dev/null 2>&1 &"
xrandr --addmode VIRTUAL1 1920x1080
xrandr --output VIRTUAL1 --mode 1920x1080 --right-of eDP1 # find your main display
screen -X -S vnc quit
killall x11vnc
# adjust postion 1920x1080+3511+180, i.e. 3511+180 accordingly
# i have different resultion display so had to move.
screen -dmS vnc  x11vnc -connect 10.0.0.2:5500  -display :0 -clip 1920x1080+3511+180 -wirecopyrect  -viewonly --nossl -ncache 10 -ncache_cr

#!/bin/bash

#Run VNC server in remote device. 10.0.0.2 is my machine which has monitor connected.

ssh root@10.0.0.2 "nohup /root/vncserver.sh > /dev/null 2>&1 &"

xrandr --addmode VIRTUAL1 1920x1080

xrandr --output VIRTUAL1 --mode 1920x1080 --right-of eDP1 # find your main display

screen -X -S vnc quit

killall x11vnc

# adjust postion 1920x1080+3511+180, i.e. 3511+180 accordingly

# i have different resultion display so had to move.

screen -dmS vnc x11vnc -connect 10.0.0.2:5500 -display :0 -clip 1920x1080+3511+180 -wirecopyrect -viewonly --nossl -ncache 10 -ncache_cr

In server Machine (LAN address 10.0.0.2)

if [[ $(ps -ef | grep -c vncviewer)  -ne 1 ]];
then
    echo "Running"
else
   export DISPLAY=:0.0;
    vncviewer -listen 0 -fullscreen -owncmap -viewonly;
fi

if [[ $(ps -ef | grep -c vncviewer) -ne 1 ]];

then

echo "Running"

else

export DISPLAY=:0.0;

vncviewer -listen 0 -fullscreen -owncmap -viewonly;

You will need to install VNC Viewer in client side.

Kindle is Super awesome !

Because of its e-ink display. I wanted a display to present data which has – Least power consumption, Not painful to eyes & obviously one which doesn’t emit blue light.
E-Ink displays fit perfectly to my requirement – acquiring a display which can be driven using Raspberry Pi or Arduino is hard, size/cost ratio is much higher.

On googling I found some display modules which were more or near to 70-80$ – even smaller display – which impulsed me to get a Kindle Touch (8th Generation) at around 74$ approx.

Kindle comes with an experimental browser but it is narrowed version of WebKit, which is pretty useful if you want to display static content or just want to make a control panel, it can easily render normal websites which use js/CSS & works pretty well. But support for HTML5 is almost absent – so you can’t use WebSockets to push data, using long polling/fast polling is only solutions so far.

Moreover, there was another problem which I had to fix – Kindle has fixed timeout which sends it to sleep mode – for mine it was 10min, after digging I found you can use ~ds or similar but for me, nothing worked.

We can only hope that support to remove timeout or change timeout period will be added in future releases. I think old kindle supports.

If you can’t change timeout or you want to use few other features I suggest you to jailbreak. Follow steps mentioned here http://www.mobileread.com/forums/showthread.php?t=275877 , Don’t jump, It works for kindle touch 8th generation. Tried, tested, working ! For KT3 you will need to install MRPI along with KUAL. Once done your kindle is officially out of warranty 😀 . Post that you need to install USBNet – it will allow you to ssh to your kindle. All this will allow you to execute “lipc-set-prop com.lab126.powerd preventScreenSaver 1″ this on the kindle. It will simply disable screensaver. 🙂

Once you have your kindle whose screen doesn’t lock you can simply go & execute a simple nodejs script to push data.

Note : Kindle doesn’t support WebSocket & none of transport methods in socket.io except “polling”.

Below is nodejs server code :

var http = require('http'),
	fs = require('fs');
	//sanitize = require('validator').sanitize;
	
var app = http.createServer(function (request, response) {
	fs.readFile("client.html", 'utf-8', function (error, data) {
		response.writeHead(200, {'Content-Type': 'text/html'});
		response.write(data);
		response.end();
	});
}).listen(1337);

var io = require('socket.io')({
    "polling duration": 60,
    'log level' :1
}).listen(app);

io.set('transports', [ 'polling']);

io.sockets.on('connection', function(socket) { 
	socket.on('message_to_server', function(data) { 
		var escaped_message = (data["message"]);
		io.sockets.emit("message_to_client",{ message: escaped_message }); 
	});
});

var http = require('http'),

fs = require('fs');

//sanitize = require('validator').sanitize;

var app = http.createServer(function (request, response) {

fs.readFile("client.html", 'utf-8', function (error, data) {

response.writeHead(200, {'Content-Type': 'text/html'});

response.write(data);

response.end();

});

}).listen(1337);

var io = require('socket.io')({

"polling duration": 60,

'log level' :1

}).listen(app);

io.set('transports', [ 'polling']);

io.sockets.on('connection', function(socket) {

socket.on('message_to_server', function(data) {

var escaped_message = (data["message"]);

io.sockets.emit("message_to_client",{ message: escaped_message });

});

Below is code of client.html

<!DOCTYPE html>
<html>
	<head>
		<script src="/socket.io/socket.io.js"></script>
		<script type="text/javascript">
			var socketio = io.connect();

			socketio.on("message_to_client", function(data) {
				document.getElementById("chatlog").innerHTML = ("<hr/>" + data['message'] + document.getElementById("chatlog").innerHTML);
			});

			function sendMessage() {
				var msg = document.getElementById("message_input").value;
				socketio.emit("message_to_server", { message : msg});
			}
		</script>
	</head>
	<body>
		<input type="text" id="message_input"/>
		<button onclick="sendMessage()">send</button>
		<div id="chatlog"></div>
	</body>
</html>

<!DOCTYPE html>

<html>

<head>

var socketio = io.connect();

socketio.on("message_to_client", function(data) {

document.getElementById("chatlog").innerHTML = ("<hr/>" + data['message'] + document.getElementById("chatlog").innerHTML);

});

function sendMessage() {

var msg = document.getElementById("message_input").value;

socketio.emit("message_to_server", { message : msg});

}

</script>

</head>

<body>

</body>

</html>

Voila – It works !

Below is video of working in case you want to see demo before getting hands dirty 🙂

Warning & Update : This method might consume more power than expected, as experimental browser has loading status – which continuously refreshes a section of the screen. To overcome this problem I will be polling server with long interval difference – which will be adjustable by the server.

Note for nerds : Since this method uses browser – it’s more flexible – but if you are possessive about power consumption & screen space – You can use JAVA to develop kindlet application. Lightweight pub/sub protocols like MQTT should help you in the way.

Designing a wall holder : You can google for covers or design own or use some double sided foam tape. Since i had access to 3d printer i got two of http://www.thingiverse.com/thing:832273 printed & hung it on the wall – it just helped me in reading few books apart from using it only as display. SWAP!

Use it as :

Scoreboard
Notification
Weather system
Wallpaper slideshow
News/RSS feeds display
Home automation control
Anything
Book reader 🙂

At the end, even if you place it behind your monitor it won’t hurt or push the new data to your eyes & spoil the code castle you were building.

Tag: hack

Adding a display over network !

Kindle Universal Dashboard