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DisplayLink external DVI/VGA display WORKS! Now on to fine tuning it.

Discussion in 'General Discussions' started by hmc, Nov 28, 2012.

  1. hmc

    hmc Active Member

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    Direct link to DisplayLink tutorial in the Wiki:


    http://pandorawiki.org/Software_projects/OS/Slackware/Advanced_usage/USB_graphic#Display_Link


    --------


    Hi guys,


    thanks to Linux-SWAT helping me a lot, I could make my DisplayLink adapter work with the Pandora under Slackware (SL4P).


    The method described here should in theory make any DisplayLink compatible adapter work.


    What is DisplayLink?


    DisplayLink is a technology allowing to drive a DVI or VGA display connected (via the DisplayLink adapter) to the USB port of a computer. It can use resolutions far beyond the Pandora's 800x480 pixels. I used a 17" VGA TFT display with 1280x1024 pixels.


    This, together with using an external keyboard and mouse, makes working on the Pandora at home almost a desktop-PC-like experience.


    IMG_0030.jpg


    (btw: if you're wondering: The external keyboard/touchpad combination on this photo is a Speedlink SL-6498-SBK FUTURA, using 2.4GHz wireless technology. Works very nicely on the Pandora's USB OTG port with an OTG adapter. At home one would probably simply connect a USB hub to the Pandora, and the hub would connect all at once: DisplayLink, keyboard, mouse, maybe network. A complete USB docking station! :D )


    Additional use cases:


    Also, it would allow to connect a projector and do presentations with the Pandora.


    What's not really possible with DisplayLink is watching movies or playing most games, as the USB interface's bandwidth does now allow for too much movement on the screen. DisplayLink compresses the image data losslessly, mainly based on avoiding to transfer data of parts of the image that did not change. So e.g. for text processing, only very little data has to be transmitted and only little CPU power is needed.


    But for movies and games, the TV Out interface is very suitable.


    My current status as of 2012-11-28:


    What's possible for now is this:


    You plug in the DisplayLink adapter, then reboot the Pandora (or at least restart the X server). Depending on how the setup is configured via /etc/X11/xorg.conf, you then either have only the external display (Pandora's display is black), or a combination of both, with the desktop spanning both screens (you can move windows across both screens or even make a window span both screens).


    Cloning the Pandora's 800x480 screen to the external display is also said to be possible, but I couldn't make that work yet.


    Most important To-Dos as of 2012-11-28:

    • Port the DisplayLink solution to SuperZaxxon firmware (need help with that)
    • Enable hotplug (so no X server restart is needed after connecting / disconnecting the adapter. This ought to be possible somehow)
    • Make cloning of the Pandora display work (it's only a matter of finding the correct xorg.conf entries I guess)


    Some more photos:


    The green screen is a good sign (green as the hope :rolleyes: ): This means that the DisplayLink driver works and talks correctly to the adapter, it only does not get any input via its framebuffer device (/dev/fbX) yet:


    IMG_0032.jpg


    Desktop of Pandora extended to above and main screen (with task bar) is on the DisplayLink screen. You can see the browser window on the DisplayLink screen also spanning the Pandora's screen at the bottom:


    IMG_0027.jpg


    With such an extended desktop, you can of course also arrange one windows per screen, to have a convenently partitioned work space:


    IMG_0030.jpg


    Here you can see the configuration, where only the DisplayLink screen is active, and the Pandora's screen is dark:


    IMG_0386.jpg


    And this is my first (failed) attempt to clone the Pandora's screen. You can see the upper left area with the file manager window is indeed cloned, but the screen dimensions and resolutions don't match yet:


    IMG_0038.jpg


    Okay, so how did we achieve that?


    Here is what I did, according to the great advice of Linux-SWAT (THANKS again!)


    (I removed the tutorial from this forum post and moved it to the Wiki now.


    Click here:



    http://pandorawiki.o...ic#Display_Link)


    Help to improve the setup and port to SuperZaxxon!


    - As stated in the tutorial, one of the most annoying things about this setup is, that X needs to be restarted when DisplayLink is connected or disconnected.


    That can certainly be automated via hotplug in some way. Maybe even the restart isn't necessary. I don't know yet. Hints are welcome!


    - It would be great, if all that also worked in SuperZaxxon. Linux-SWAT has asked notaz already, to include the udl driver into the SZ kernel. However, someone would need to compile udlfb and the X driver for SuperZaxxon, too. I may try this soon, but if anyone else wants to do that, feel free please!


    - Donate for Linux-SWAT's project!


    Have fun!


    Daniel
     
    Last edited by a moderator: Feb 6, 2016
  2. _wb_

    _wb_ Microbe Staff Member

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    Neat!
     
  3. Linux-SWAT

    Linux-SWAT Advanced Member

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    Nice guide !


    And nice keyboard too ;^).


    I came across two questions:


    1- The adapter lists:



    Code:
    
    [ 236.598846] udlfb: 640x480 @ 85 Hz valid mode
    
    [ 236.598846] udlfb: 800x600 @ 56 Hz valid mode
    
    [ 236.598876] udlfb: 800x600 @ 60 Hz valid mode
    
    [ 236.598876] udlfb: 800x600 @ 72 Hz valid mode
    
    [ 236.598876] udlfb: 800x600 @ 75 Hz valid mode
    
    [ 236.598907] udlfb: 800x600 @ 85 Hz valid mode
    
    [ 236.598907] udlfb: 1024x768 @ 43 Hz valid mode
    
    
    But not the OP's 800X480.

    As i'm not a multi screen guy, i don't know how to get around this issue.



    2- As the udlfb module is compiled alongside the kernel, i finally wonder if the



    Code:
    
    su -
    
    git clone http://git.plugable.com/webdav/udlfb/
    
    cd udlfb
    
    make
    
    make install
    
    depmod -ae
    
    
    is mandatory ?
     
    Last edited by a moderator: Nov 28, 2012
  4. F_Slim

    F_Slim IDDQD

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    Nice work! These things don't come cheap though ... but being able to attach the Pandora to a beamer and give a talk using Slackware and LibreOffice (I guess that works?) might be worth it.


    However, this would have to work right away to be feasible (plug it in and go). Is it possible to set it all up to pass a 1024x768 signal the way I want once and that's it, or will it require tweaking each time you use it (or depending on the screen/beamer attached)?
     
  5. Linux-SWAT

    Linux-SWAT Advanced Member

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    Libre Office compilation failed on OP CC 256M ram. Maybe i can build it on a 1GHz unit (some Gentoo forum reported that 512M was the low limit).


    I'm currently requesting donations to complete my original preorder to a 1GHz:





    Then i will give it a last try.


    For now, i'll ship AbiWord and Gnumeric in my next release.
     
  6. hmc

    hmc Active Member

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    I don't know either. Now that you mention it, this could be the reason, why my Clone attempt failed. Of course I tried to configure the external screen to 800x480 via xorg.conf, but that failed. I didn't know why. Too bad. Hopefully there will be some solution. 640x480 would probably be a solution. But that would be sad.

    Maybe other DisplayLink adapters are capable of the 800x480 mode? Anyone able to check this?







    I wondered about that, too. I simply did it, because I trust you so much. ;-)


    Someone replicating this setup might skip this step and report, if the driver works anyway.


    The goal is to have a plug-and-play (including hotplug) setup.


    But we're not quite there yet.


    Btw: Once this solution is ported to SuperZaxxon firmware, at least the LibreOffice issue would be solved, as LibreOffice is available there using PanDebian.


    But I really hope, that Linux-SWAT will be successful in compiling LO for SL4P, too.


    Maybe I can help with that? I have SL4P and a 1GHz Pandora. What should I do?
     
  7. Linux-SWAT

    Linux-SWAT Advanced Member

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    I think it would be best to use 800x600. Should display little black borders.


    I will upload the RC5 soon (in fact i made three attempts, and always found many new bugs/things to polish when testing the produced image).


    If you're ok for the following, i will include all needed stuff in it, so you will just have to set max MHz, disable X, run a script, and wait approx. three days (don't forget to plug the AC).


    --EDIT:


    Oh, a 16GB or more card is needed.
     
    Last edited by a moderator: Nov 29, 2012
  8. Askarus

    Askarus Advanced Member

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    That sucks!!


    I don't have any use for my Laptop any more. :p .


    You guys rock. That's amazing news. I can now do all my Presentations on my Pandora.


    @ hmc:


    I have some questions.


    As DisplayLink devices are quite expensive It'd be great if you could give me some Link to a working device (the one you're using).


    What about battery consumption? How long will your Pandora life with that power hungry DisplayLink.


    Are there better devices than the one you use? I don't think there's more resolution needed than the one you use (would also be nice) but better performance is always welcome.


    @ Linux Swat.


    Great to see a new Version of Slackware coming.


    Don't worry, I have a 32 Gig SD-card for Slackware.


    @ Both.


    THANKS


    for making this possible. Having it on Zaxxon would be even more awesome.
     
  9. hmc

    hmc Active Member

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    On a 4:3 screen this would probably look awful (compressed horizontally). But I'll try.


    On a widescreen it may be much better. Will test that, too.

    Great. Thank you!


    I'm so sorry about that! Not. :D

    I think it's this one:


    http://www.amazon.de...54174889&sr=8-1


    But not sure. The model numbers on the devices are not given in the Amazon offers.


    On mine, there is written model # WS-UGA12D1.


    In theory all DisplayLink compatible adapters should work (read udlfb documentation).


    No idea yet.


    Of course it needs battery. It gets quite warm while in use. So I guess it's near to the 500mA max. current draw of USB.

    I don't have an idea about that either. In general you should get more performance the lower the resolution is, that you use (with comparable display content, since performance is highly dependent on display content due to the way DisplayLink compresses the data).
     
    Last edited by a moderator: Nov 29, 2012
  10. Askarus

    Askarus Advanced Member

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    Thanks for your answer.


    After checking the link I have some further question.


    This adapter dooesn't support 480x800.


    Willl I get problems when cloning the Pandora screen (which will hopefully work soon?)


    Sipmly run System Info and wait some seconds. That will give DETAILED info about everything battery and CPU and RAM rlated :) .

    Will there be some overheat after some while or may I use it for some hours?

    I know.


    As e have "high res" 600x800 projectors in university I don't think I'll get problems here.


    On my HD monitor at home I can do some hardcore stuff :D .


    Go for Zaxxon.


    Come one Notaz.


    Go for Slackware R5 with DisplayLink stuff included.


    Come one Linux-Swat.


    :D :D :D :D
     
  11. F_Slim

    F_Slim IDDQD

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    That's perfect then!


    oh damn, I also just lost the need for my Laptop ... and I just bought a new one :( ^_^


    I would want to use a resolution of 1024x786 for doing presentations. I could probably live without having the slides on the Pandora display, some kind of "presentation mode" to show notes on the Pandi and the slides on the beamer would of course be great ... (as added bonus feature at some point in the future once the basics work is what I want to say)


    It might be better to use a powered USB hub for the DisplayLink. Less danger to fry your USB port and I guess the battery in the Pandora would last for the entire conference ;)
     
  12. hmc

    hmc Active Member

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    See Post #6 .


    One way could be to use 800x600 for the external display. But I don't know how this will look like.


    Or use 640x480 for both screens. However, this will limit usability of the Pandora screen in that scenario a bit.

    Okay, will do this tonight and report.

    No. The doesn't get hot, just the adapter is noticeably warm. Not hot either. The warmth just suggests to me, that current draw must be several 100 mA. It's just a feeeling. I haven't measured. No danger of overheat. I let my DisplayLink adapter connected and active for almost 50 hours now, and it still works and is not too hot. (Pandora on AC, of course).

    Askarus and F_Slim, why not donate your laptops to some 3rd world's children then? You get the laptop replacement here for free (i.e. DisplayLink support; you have bought the Pandora anyway), so that's not a loss for you, but a big gain for those children. ;-)

    Sure, that would be cool.


    With a desktop spanning both displays, you can do something like that already. Put the program window with your notes (possibly a text editor) onto the the Pandora's screen, and put the presentation display onto the external one. I haven't tested any presentation program yet. It may depend on the individual application, if it supports to place the full-screen presentation onto a specific display in a multi-monitor setup. I know that at work, when doing presentations with PowerPoint, if you activate a full-screen presentation, the presentation will always be presented on the wrong screen. ;-)

    No danger to fry the port I think, even without a hub. USB electronics should be safe against frying. The USB device reports via the USB protocol, how much current it needs, and if the USB port cannot deliver that much current, the device is deactivated. I know the DisplayLink adapter (my model at least) reports to ned 500 mA. But many devices do, although they actually need much less.


    In my many years of intensive computer usage, I managed to fry only one USB port. That was one of an IBM notebook about 5 years ago, when I connected some special equipment to it, that must have been faulty, bringing some voltage level onto the data lines of the USB connection, that the USB chip of the laptop couln't stand, I guess. USB is quite safe. As is/was RS232 serial ports. There you could short-circuit any pair of lines for an arbitrary time without damaging the port.


    Of course, applying some additional voltage to such a port will always destroy it, if the voltage is too high.
     
    Last edited by a moderator: Feb 6, 2016
  13. Askarus

    Askarus Advanced Member

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    Right.


    I have to get one of those powered hubs.


    It's also good when using a HDD.


    EDIT:


    @ hmc:


    You posted while I was typing.

    Dammit.


    I should look closer and remember that stuff then.

    Great.


    (50 hours? are you crazy?? ;) )

    Better not.


    I need some Windows programms for University (unfortunately).


    I'm looking forward to see the System Info resullts.


    As you're responsible if the device you posted the link does not work I think I can savely buy one :p .
     
    Last edited by a moderator: Nov 29, 2012
  14. hmc

    hmc Active Member

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    I agree, that when working at home or in the office, a powered hub is a good way to relieve the Pandora from high current draw, and to make sure that everything connected to the hub will work flawlessly.


    But for presentations, for on-the-go work, in meetings etc., needing to rely on a powered hub would be a nuisance.


    So my recommendation would be to make sure to only buy equipment that also works without (any, especially a powered) hub.


    For connecting keyboard and mouse (USB 1.1), you would either need a hub for connecting that to the lagre USB port or you need a USB OTG adapter to connect it to the small USB UTG port. The latter is much more convenient, IMO, as such an adapter is much smaller than the smallest hub.


    The alternative would be a Bluetooth keyboard and mouse.


    However, I've had bad experiences with all Bluetooth keyboard so far: After a small timeout, somehow it seems to change to idle mode, and it needs a key press to return into busy mode. That means, the first key press after that timeout is eaten by the keyboard.


    his is not good for yping. ;-)


    See here for the corresponding thread:
     
  15. ibisum

    ibisum Well-Known Member

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    I want to use my Pandora with my LapDock. I guess this is one way to do it. Nice work!
     
  16. F_Slim

    F_Slim IDDQD

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    I can recommend this USB Hub:


    http://www.amazon.de/Hama-USB-2-0-Hub-Bus-powered/dp/B0015LAUBW/ref=sr_1_12?s=computers&ie=UTF8&qid=1354192996&sr=1-12


    in combination with this adapter:


    http://www.conrad.de/ce/de/product/511929/Egston-DC-Adapterset-zur-Steckererweiterung-Passend-fuer-Netzteile-mit-DC-Hohlstecker-55-x-21-mm/SHOP_AREA_17455&promotionareaSearchDetail=005


    because then you can at least power it with the power-adapter of the Pandora (probably there are other Hubs where this works as well.)


    But I fully agree that anything not needing a Hub or adapter is always a better solution.
     
  17. Linux-SWAT

    Linux-SWAT Advanced Member

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    The current draw was reported by lsusb -v
     
  18. hmc

    hmc Active Member

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    The true one or the maximum nominal one defined by the manufacturer? I think it's the latter...?
     
  19. Linux-SWAT

    Linux-SWAT Advanced Member

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    I don't know.
     
  20. cube48

    cube48 Member

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    Nice to see this running. Congratulations! I hope this makes it's way to official Pandora OS too.
     

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