Daily Archives:June 2nd, 2012

Remote keyboard and mouse for your RaspberryPi

Warning – technical post ahead…

My shiny new RaspberryPi came through the door this week, and the first thing I noticed was that it was the first computer I’d ever received where the postman didn’t need to ring the bell to deliver it.

The next thing I discovered, because it came sooner than expected, was that I was missing some of the key bits needed to play with it. A power supply was no problem – I have a selection of those from old phones and things, and I found a USB-to-micro-USB cable. Nor was a network connection tricky – I have about as many ethernet switches as I have rooms in the house.

A monitor was a bit more challenging – I have lots of them about, but not with HDMI inputs, and I didn’t have an HDMI-DVI adaptor. But then I remembered that I do have an HDMI monitor – a little 7″ Lilliput – which has proved to be handy on all sorts of occasions.

The next hiccup was an SD card. You need a 2GB or larger one on which to load an image of the standard Debian operating system. I had one of those, or at least I thought I did. But it turned out that my no-name generic 2GB card was in fact something like 1.999GB, so the image didn’t quite fit. And a truncated filesystem is not the best place to start. But once replaced with a Kingston one – thanks, Richard – all was well.

Now, what about a keyboard and mouse?

Well, a keyboard wasn’t a problem, but it didn’t seem to like my mouse. Actually, I think the combined power consumption probably just exceeded the capabilities of my old Blackberry power supply, which only delivers 0.5A.

If you’re just doing text-console stuff, then this isn’t an issue, because it’s easy to log into it over the network from another machine. It prints its IP address just above the login prompt, so you can connect to it using SSH, if you’re on a real computer, or using PuTTY if you’re on Windows.

But suppose you’d like to play with the graphical interface, even though you don’t have a spare keyboard and mouse handy?

Well, fortunately, the Pi uses X Windows, and one of the cunning things about X is that it’s a networked display system, so you can run programs on one machine and display them on another. You can also send keyboard and mouse events from one machine to another, so you can get your desktop machine to send mouse movements and key presses from there. On another Linux box, you can run x2x. On a Mac, there’s Digital Flapjack’s osx2x (If that link is dead, see the note at the end of the post).

These both have the effect of allowing you to move your mouse pointer off the side of the screen and onto your RaspberryPi. If you have a Windows machine, I don’t think there’s a direct equivalent. (Anyone?) So you may need to set up something like Synergy, which should also work fine, but is a different procedure from that listed below. The following requires you to make some changes to the configurations on your RaspberryPi, but not to install any new software on it.

Now, obviously, allowing other machines to interfere with your display over the network is something you normally don’t want to happen! So most machines running X have various permission controls in place, and the RaspberryPi is no exception. I’m assuming here that you’re on a network behind a firewall/router and you can be a bit more relaxed about this for the purposes of experimentation, so we’re going to turn most of them off.

Running startx

Firstly, when you log in to the Pi, you’re normally at the command prompt, and you fire up the graphical environment by typing startx. Only a user logged in at the console is allowed to do that. If you’d like to be able to start it up when you’re logged in through an ssh connection, you need to edit the file /etc/X11/Xwrapper.config, e.g. using:

sudo nano /etc/X11/Xwrapper.config

and change the line that says:


to say:


Then you can type startx when you’re logged in remotely. Or startx &, if you’d like it to run in the background and give you your console back.

Allowing network connections

Secondly, the Pi isn’t normally listening for X events coming over the network, just from the local machine. You can fix that by editing /etc/X11/xinit/xserverrc and finding the line that says:

exec /usr/bin/X -nolisten tcp "$@"

Take out the ‘-nolisten tcp’ bit, so it says

exec /usr/bin/X "$@" 

Now it’s a networked display system.

Choosing who’s allowed to connect

There are various complicated, sophisticated and secure ways of enabling only very specific users or machines to connect. If you want to use those, then you need to go away and read about xauth.

I’m going to assume that on your home network you’re happy for anyone who can contact your Pi to send it stuff, so we’ll use the simplest case where we allow everything. You need to run the ‘xhost +‘ command, and you need to do it from within the X environment once it has started up.

The easiest way to do this is to create a script which is run as part of the X startup process: create a new file called, say:


It only needs to contain one line:

/usr/bin/xhost +

Now, when the graphical environment starts up, it will allow X connections across the network from any machine behind your firewall. This lets other computers send keyboard and mouse events, but also do much more. The clock in the photo above, for example, is displayed on my Pi, but actually running on my Mac… however, that’s a different story.

For now, you need to configure x2x, osx2x, or whatever is sending the events to send them to ip_address:0, where ip_address is the address of your Pi. I’m using osx2x, and so I create the connection using the following:

Once that’s done, I can just move the mouse off the west (left-hand) side of my screen and it starts moving the pointer on the RaspberryPi. Keyboard events follow the pointer. (I had to click the mouse once initially to get the connection to wake up.)

Very handy, and it saves on desk space, too!

Update: Michael’s no longer actively maintaining binaries for osx2x, and the older ones you find around may not work on recent versions of OS X. So I’ve compiled a binary for Lion(10.7) and later, which you can find in a ZIP file here. Michael’s source code is on Github, and my fork, from which this is built, is here.

Summer fruit pudding

There’s something rather fruity about the fact that my new RaspberryPi is being powered by an old Blackberry power supply.

Which used to be on the Orange network.

And that I log in to it from my Apple.

Hope it doesn’t turn out to be a lemon.

Reach for the Skypes

I love Skype – it’s one of the most-used utilities on my Mac, and a vital business tool.

There are some who don’t understand this, chiefly because they think Skype is about making cheap phone calls. Of course, it’s very good at that too: I dread to think how much I might have clocked up in phone bills on my last holiday if I hadn’t had Skype and the hotel wifi network. It’s also the easiest way I know to set up conference calls.

But mine is configured so that when I double-click on a name, it pops up a chat window, not an audio connection. Though, I admit, the first thing I type is often ‘Are you free for a quick call?’ But that’s so much more polite and… well, British… than simply bursting a ringing phone into someone’s day without so much as a ‘by your leave’.

At other times, the chat window is all I want. I can drop quick text messages in there, like ‘Can you remind me of the login for this URL?’, and it’s generally quicker and less hassle for everyone involved than any other way of transferring that information.

The real power comes when you’re combining the two – a conversation and a chat window. If you’ve ever tried dictating a URL to someone so that you can peruse a web page together while talking on the phone, you’ll appreciate the power of a cut, paste and click to keep things moving along. And, gosh, I haven’t started talking about video calls, about screen-sharing, about file transfer… And the fact that, if you’re willing to pay a few pence, you can send text messages from it, which is so much easier than typing on a phone keyboard.

Anyway, the degree to which you too will discover this brave new world of communicative wonderfulness depends on two things:

  • How many of your friends know your Skype address (so put it in your email signatures)
  • Whether you run it most of the time (so set it to start up when you log in)

Skype first became really important for me when one of my former companies was headquartered in a house with a studio in the garden. Half of the team worked in the house, and half in the shed, so having a quick, lightweight method of communication between the two was important.

When we outgrew that, we moved to an open-plan office. Open-plan offices are things that people used to think were a good idea because they hadn’t tried them. Then commercial landlords realised that it was a much more convenient way to let out office space, so they told their clients, “Oh yes, everybody’s doing this now”. They still continue to exist because the people making the property decisions aren’t writers or software developers, who need peace, quiet and concentration, punctuated by a modicum of social interaction over caffeine-dispensing equipment, to be really productive.

So, in many offices, you have big open spaces filled with people wearing headphones and listening to music loud enough to drown out the distractions of the phone calls around them. They’re more isolated than if they were in different rooms. Managers seem to like this arrangement, because when they walk in they see large numbers of people beavering away, and they fail to realise that those people are beavering about two-thirds as efficiently as they might beaver. Factor that into your rent-per-square-foot…

Anyway, I digress, but the result was that Skype continued to be important when we were all in one room, not to talk to people at the far end of the garden, but for reaching those who were just a couple of desks away but in a completely different musical genre.

If you spend much time sitting in front of a computer, you owe it to yourself to run Skype and get your friends and colleagues doing so too. Yes, there are other systems, but few that run on Windows, Linux, Mac, Android and iOS and give you such a variety of different communication styles.

One final tip for Mac users: the current version of Skype, version five-point-something, is generally agreed to be horrible. Well, not horrible, exactly – in fact, I think it looks quite nice – but it does have ideas above its station and wants to take over your entire desktop. Fortunately, this feeling that it’s got just a bit too big for its boots is so widespread that the previous version, 2.8, is still available from the Skype website on its own download page a couple of years after its supposed replacement was rolled out. Grab a copy and make a backup, in case it goes away…

© Copyright Quentin Stafford-Fraser