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-   -   rdesktop, a killer application for raspberry pi (http://www.diyaudio.com/forums/everything-else/224004-rdesktop-killer-application-raspberry-pi.html)

counter culture 21st November 2012 02:09 AM

rdesktop, a killer application for raspberry pi
 
I got a raspberry pi early on in the ordering process.

I'm an enthusiastic coder, so stuff like the pi is grist to my mill.

Imagine my disappointment when I discovered that I couldn't get it to play music worth a damn out the USB port. It plays stuff, but with great gaps in the playback. As far as I can determine this is a problem with the hardware and it's not fixable.

I can't determine the exact situation since there are people out there claiming to have USB DACs working OK and others talking about a USB hardware problem and the timelines are confused. Mine certainly isn't working

I have thought about buying a spare TV and trying the HDMI sound, but I don't really need another TV. I'd have to struggle to get access to the back of one of the existing TVs to try it, I'll get around to it eventually I guess.

So I disconnected the pi, chucked it in a box and left it for a few months.

A couple of days ago I noticed the Google Nexus 7. That looks like quite a handy tablet, so I started to wonder about doing circuit design under Android.

My most recent laptop died a while ago, and I haven't replaced it. It always had a noisy fan and it irritated my wife. I don't need a laptop now that I'm retired and I do everything on an old desktop. The desktop too is noisy, so I have to sit in another room to use it, so it's a bit unsociable, it means we run 2 TVs instead of one, 2 room heaters, and I spend a lot of time doing design, it's my main interest.

I normally use a very nice tool from Labcenter called Proteus (Isis and Ares). It's a very good tool that was bought for me by a former employer. I have experience of numerous PCB design tools, I won't enumerate them all here, but they range downwards from Mentor Graphics, which is the most comprehensive and capable of tools, and probably the most expensive. For all that, Proteus has the most straightforward interface and produces the most easily comprehensible and legible schematics. My main complaint about it is that although it is growing closer to using a Windows standard UI, it didn't start out as a native Windows application, and this still shows a bit in the version I have.

So suddenly I remembered the raspberry pi. I've got a nice full-HD HDMI monitor (without sound) that I bought to use with it, it's one of the reasons I don't want to buy another small TV. I've also got a wireless keyboard and mouse for it.

The pi itself struggles with running a lot of things, a browser with a couple of tabs open is about as much as it can cope with without slowing down a lot and glitching.

My desktops run Win XP (or linux). I don't like the way Microsoft have tried to sell me new operating systems. XP professional did everything we needed in a business context, so I keep the machines I have going with upgrades and I don't have to poke around looking for where Microsoft have moved some essential setting to in Win 7 unless it's to help out a friend.

It suddenly occurred to me that I could use the software I already have and like if I could get up a remote desktop.

Exporting a display under linux is child's play. It's something the system does natively without effort for linux-to-linux, but I wasn't sure about Win XP to linux.

As it turns out it wasn't much more difficult. Obviously you need both computers connected to the same LAN and you need to know the IP address of the host computer. You can determine this on the Win XP box by going Start Menu->Run->cmd, which will give you a terminal window (used to be called a DOS box). Type 'ipconfig' without the speech marks and press return. Amongst the information displayed you will find the machine's IP address.

You need a password login to Win XP, so if you have your system set up for passwordless login, as my home systems are, you have to change this.

Go Start Menu-> right click My Computer and select Properties. Select the 'Remote' tab and click the checkbox 'Allow users to connect remotely to this computer'. Click the button 'Select remote users'. This will pop up a box called Remote Desktop Users. This box has a blue link to User Accounts. Here you can modify an existing user to have a password or create an additional user specifically to use for remote connections. You can add this user to the list of remote users from the Remote Desktop Users popup window, it's straightforward. If you have security concerns you can configure the Windows firewall to only accept remote desktop connections from a specified IP address. I don't allow inward remote access through the router from the WAN any case.

Now go to the raspberry pi. It needs to have a working Internet connection, at least for the purposes of installing rdesktop. Open a terminal window and type 'sudo apt-get rdesktop'. This will install rdesktop, the linux Remote Desktop client.

Once the install process is complete you can type "rdesktop -u 'My Windowsusername' -f xxx.xxx.xxx.xxx" where xxx.xxx.xxx.xxx is the IP address of the Win XP host. You only need the single speechmarks round the username if it has a space in it, and obviously you don't type the double speechmarks, they're just there to show you what to type.

This wil pop up a window showing a login screen for the remote desktop with the Windows username filled in. All that is required is to type the password and hit return. A full-screen remote desktop will replace your regular raspberry pi desktop. You can toggle between the Windows and the pi desktops by pressing Ctrl, Alt, Enter. You will see the Windows taskbar when you mouseover the bottom of the screen, but if it is overlaid by the linux taskbar as it will be on occasion, press Ctrl, Alt, Enter

The remote desktop on the pi is remarkably responsive, not as quick as on the host computer, but surprisingly useable, I'm typing on the raspberry pi via an instance of Chrome running on the remote Win XP machine right now.

Now I have a quiet, full-screen, capable computer running all my familiar software and saving the files I'm working on to where I most want them without the hassle of transferring them with a USB stick or whatever. I can run LTSpice simulations with only a minor delay for the screen updating. The raspberry pi has gone from being a disappointment to something pretty damn useful.

Now, if I could just get the sound going...


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