DoubleSight USB Monitor compatibility with Arch

[sdjf]

I am asking this in the Arch forum as I want feedback from my fellow Arch users.

I need to get a monitor for my Pi (which currently run headless) but need something very small (under 12 inches) and am looking at the DoubleSight DS-90U, 9 inch monitor. It is a standard display, not touchscreen.

I am worried this might not be possible to get to work on Arch on the Pi as my primary monitor because it is a USB monitor. I am finding old posts saying people got such monitors to work, but needed custom kernels.

I do not have any experience with monitors at all, or how they work, so I apologize if the answer is obvious to people who know and understand this stuff better.

My question is whether we have appropriate drivers for this in Arch on the Pi, and how I would go about telling the Pi to use the USB device as the primary display, so my keyboard input all went to it rather than a nonexistent HDMI/composite display.

I do understand it will add a load to USB, but all the other small displays I can find either have poor image quality (composite) or do not have user replaceable batteries, and I want hardware that will not have to get thrown away because the battery no longer holds a charge.

Thanks,
sdjf

[sdjf]

I went ahead and bought the DoubleSight DS-90U since we have the driver udlfb in the kernel.

Could not find an lsusb listing this monitor anywhere on the web so, for anyone else hunting, here it is, apparently when people say a monitor is a DisplayLink device, they mean it is a displaylink chip:

Bus 001 Device 025: ID 17e9:02ff DisplayLink

Now I am clueless about what to do next. It is seen by the driver but I do not understand any of the documentation saying how to get these working.

I do not need this to work in X, I just need commandline right now. Anybody able to help?

[pepedog]

A good sign is screen goes blue when plugged in.
What device name appears in /dev

[sdjf]

The screen on the doublesight looks kind of white to me when I turn it on (but it actually is either light green or light blue, depending on the viewing angle). Since this is USB, the power and plugging in to Pi are connected. But it does have an on/off button too.

And it mounts on /dev/fb1, tried echo hello > /dev/fb1 but nothing happened.

Does it require configuration somewhere if I want to just use it as primary display without going through xorg? Resolution is 1024x600

[pepedog]

I got a feeling console framebuffer won't work, only xorg
Maybe use xf86-video-fbdev or https://aur.archlinux.org/packages/xf86 ... splaylink/
https://bbs.archlinux.org/viewtopic.php?id=164385

[sdjf]

Thank you.

I have not been able to successfully update my May 2013 system kernel 3.6.11-11 due to package conflicts. Nor get ssh to work with the June kernel. Running headless, ssh is essential.

xf86-video-fbdev wants me to uninstall my vnc server - I am afraid to try that as urgently needing VNC access now for spreadsheets, and no spare SD card to play with (two are on the way).

I will try that displaylink package from AUR - looks like it flagged as out of date and is older, so might work.

there also is something that copies fb0 to fb1 (fbcp) but it says it will only with images July or later.

the second page I cannot figure out. seems he basically is saying cannot get stuff to work.

[sdjf]

Compiled the displaylink package from AUR, it did not work out, the module I ended up with has error message when try to insmod.

So, cleared a 4GB card and am going to try a fresh install of May image (kernel 3.6.11-11) that I know I can ssh into, and then see if I can successfully update it so can install the xorg fb dev driver. Doing fresh install so there are not so many packages to update. If can get required xorg packages installed and even just one thing like lxterminal working with the monitor, that is what aim to do before install all the other packages that need.

[sdjf]

Got May Arch image for Pi updated to linux-3.6.11-18 without any problems, now need help with how to get the xorg driver to attach to my DisplayLink Device. udlfb attaches to the device but I understand that it also has to get handled by xf86-video-fbdev.

Here is what I have installed for fbdev.

Code: Select all

alarmpi# pacman -Q xf86-video-fbdev
xf86-video-fbdev 0.4.4-1
alarmpi# 

alarmpi# ls -l /usr/lib/xorg/modules/drivers/fbdev_drv.so
-rwxr-xr-x 1 root root 17036 Sep 25 11:18 /usr/lib/xorg/modules/drivers/fbdev_drv.so
alarmpi#

But this does not seem to be a regular driver, cannot insmod or modprobe it. Output below, I know there are a lot of how tos/wiki pages but they are confusing, saying udlfb is getting replaced by udl. But they still say the xorg fbdev driver is needed.

Code: Select all

 
alarmpi# insmod fbdev_drv
insmod: ERROR: could not load module fbdev_drv: No such file or directory
alarmpi#
 
alarmpi# insmod /usr/lib/xorg/modules/drivers/fbdev_drv.so
insmod: ERROR: could not insert module /usr/lib/xorg/modules/drivers/fbdev_drv.so: Invalid module format
alarmpi#
 
alarmpi# modprobe fbdev_drv
modprobe: FATAL: Module fbdev_drv not found.
alarmpi# modprobe /usr/lib/xorg/modules/drivers/fbdev_drv.so
modprobe: FATAL: Module /usr/lib/xorg/modules/drivers/fbdev_drv.so not found.
alarmpi# modprobe fbdev_drv.so
modprobe: FATAL: Module fbdev_drv.so not found.
alarmpi#

I thought maybe there is something wrong with this version of the package, but when I tried insmod or modprobe with an earlier version, on my older kernel, same thing happens.
EDIT: found out from friend that xorg drivers do not load same as kernel drivers. All it took was creating a viable xorg.conf file in /etc/X11/xorg.conf.d/ and rebooting. There was a cursor in midst of blue screen! Still figuring things out, but typing my mouse emulation commands on keyboard does affect screen...g
so, I am on the road to success, at last!!!

[wasatchwizard]

I'm wondering how this all turned out for you!? Did you get everything working as it should / as you needed?

I'm setting up a pi in the kitchen/dining area for the family to use the calendar and choremonster.com, etc. And, I'm wondering about USB monitors..

Thanks,
Kody

[sdjf]

Thanks for asking. yes, my DoubleSight monitor has worked out great. I was worried about overloading the USB driver, so have been careful not to do anything with GUI browsers yet until I am in a position to debug and repair any damages.

Maybe once or twice a week, the screen will go blank for a brief second but then restore immediately. Here is what the kernel says when that happens:

Jan 5 23:07:19 rpi kernel: [1489570.103022] udlfb: wait for urb interrupted: ffffffc2 available: 4

the same message will appear hundreds and hundreds of times if all USB goes down or my PDA whacks out and causes a crash.

But I am really enjoying this thing. The only thing I do not like is that when I use it to VNC into a friend's box over the internet, if I change to a different window (I mean, switch to my terminal on the Pi and then go back to the VNCviewer), the whole stupid screen redraws itself at the speed slower than a turtle even if nothing has changed on the screen I was on before going off to my console.

I also am getting good with mouse emulation - still have no mouse, and there are some sites that do not like my xdotool stuff going through openbox and vnc, but the emulation is working fine in spreadsheets and for copy/paste in xfce4-terminal. I was using lxterminal, and copy paste was kind of okay there, but for sure is working in xfce4 terminal, which I like better as it has more options and shows if something I have not seen yet happens in another tab.

[wasatchwizard]

Sounds like it is working fairly good.. I'm glad to hear it!! Thanks for the quick reply too!

I wish I knew more about Linux so I could help troubleshoot your error, but that looks like greek to me.. ie: past my level of usefulness!

[sdjf]

I think the error is USB driver overload, I just am careful about what I do, as I mentioned. We shall see how it handles chromium when I get around to using that instead of VNC, on browser intense websites, but I made the choice and I am happy with it.

One thing I did not mention that may help you or others, is that when I first got it working, it was on an older system, not updated completely, and X was crashing very quickly, maybe I had like 10 or 15 minutes. But once I had an SD card that was totally up to date to the system about October or November, X with this monitor became very, very stable. I had over two weeks recently without a crash - then I knocked my PDA loose from the ssh connection over USB, and the Pi whacked out, X froze, I think it was getting stuff mixed up. Fortunately, since I had the monitor and modem on a piggy backed powered hub, just turning that hub off and back on again restored my ability to ssh back in with the other PDA.

Pi had reassigned the monitor to /dev/fb2 instead of /dev/fb1 and my X was not liking that, so I just rebooted (sync then reboot) to get things working properly again.

Post back if you have trouble getting one of these recognized and working, I was going to try to do a writeup but have just been too busy with other things. Installing the right additional packages recommended by Pepedog, and placing a good configuration file in /etc/X11/xorg.conf.d/ specific to the display link monitor was essential.

[buteman]

I know it's a long time now but I have been searching as I want to use a usb monitor as only monitor on a desktop machine because I need a small screen. Did you ever get a writeup done?

[sdjf]

I know it's a long time now but I have been searching as I want to use a usb monitor as only monitor on a desktop machine because I need a small screen. Did you ever get a writeup done?

No, sorry, have been too busy and don't think I will be able to any time soon. There are too many more urgent things to take care of. What did you need to know?

I never did install chromium, I decided to wait and install chromium with Arch on my Pi 2 when I get that in a few months.

I think the things to pay attention to are mentioned earlier in this thread, as far as the USB monitor.

I think if memory is a concern, that an HDMI monitor would be better, but at the time I needed a monitor for my Pi, there wasn't anything in the way of a good cheap HDMI monitor available that met the rest of my specifications.

I do like my USB monitor but am sure my Pi would perform better if I had an HDMI one. Memory may be less of an issue with the newer models of Pi, but now that there are so many HDMI alternatives, I expect to be getting one of them instead for my Pi 2. The USB bus on the Pi is slow, and that apparently has not changed with newer models as of this point in 2015.