[WIP]Raspberry Pi as USB HDMI-out (via USB Networking) - Page 4 - maemo.org

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sulu	2012-01-16 , 10:16
Posts: 915 \| Thanked: 3,209 times \| Joined on Jan 2011 @ Germany	#31

Originally Posted by impeham

but this way you will have to manage two separate computers which is a lot of overhead.

Maybe we should define first what you mean by "manage two separate computers"?
If you want to control the Raspberry from the N900 the former needs some sort of system installed in the first place to process the commands that come from the N900. Since the Raspberry is supposed to support Debian and the N900 already runs Debian (sort of) that would be the logical choice.
Then we need some way to create an interaction between the two devices. The most commonly known way surely is VNC. x2x or Xpra might result in better performance but just like VNC they won't actually eliminate the barrier of still having two separate devices that run their own operating systems.
So what actually remains of the integration of the two devices are three things:
1. To use the N900 as a mouse and keyboard for the N900, which is only a stopgap solution since an actual mouse and keyboard will always be more comfortable.
2. To use the N900 for network connections. This can easily be achieved by attaching the N900 in PC suite mode to the Raspberry running its own completely independent Debian.
3. To use the data we have on the N900 which is a simple mass storage connection.

I was hoping to combine the strong N900's CPU (the Raspberry's will be weaker) with the Raspberry's strong GPU (it's supposed to be able to decode 1080p) and maybe even the combined RAM. Unfortunately that doesn't work at the very first step since Xpra already adds more overhead than the systems we're talking about are able to handle. And honestly Fabry's results don't seem more promising either.
So there's nothing special I see left here unless I've missed some important feature that the N900 might add to the Raspberry apart from the three I've mentioned above.
...or creating an artificial, unneeded integration just for the sake of doing it because as N900 users we want to integrate it everywhere. The Raspberry will work just as fine (or likely even better) without it.

Originally Posted by impeham

however - viewing pictures with HD output for example would be awesome i think.

Then just boot the Raspberry connected to a TV and connect the N900 containing your pictures. There's nothing magic or new about that.

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	javispedro	2012-01-16 , 11:35
	Posts: 2,355 \| Thanked: 5,249 times \| Joined on Jan 2009 @ Barcelona	#32

This is similar to what I did ages ago with a DisplayLink device:

http://depot.javispedro.com/nit/usb/xvnc2dlusb.jpg

My approach was Xvnc and then vnc2dl which is severely outdated (on modern kernels there is udlfb). VNC is not as slow as it sounds because the target DisplayLink protocol is basically VNC on steroids.

Therefore, you can run a second X server and redirect applications on Maemo just fine.

The entire setup was very slow, but usable. I used a USB mouse.

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	Estel	2012-01-16 , 19:39
	Posts: 5,028 \| Thanked: 8,613 times \| Joined on Mar 2011	#33

Originally Posted by sulu

Maybe we should define first what you mean by "manage two separate computers"?

The thing is, that using Raspberry Pi exclusively, You should mirror Your content from N900 (documents, photos, programs, etc). Not to mention things like Truecrypt encrypted partitions, if You work on those. Also, for most "productivity" things, N900 MPU is *much* better - it's not a matter of raw mhz value, check SoC specification. Raspberry Pi SoC is *really* strange thing. I agree that it performs well when it comes to DSP, though.

As we have our N900's always with us, we tend to work on it on the go - sitting in train, for example, there is no sane way to work on Raspberry Pi (no screen). Using Pi exclusively, we would need to sync everything we did on N900, when - later - we have access to monitor with DVI input. in practice that would mean - most of the times - more overhead due to rsyncing, than just using N90 0with it's internal screen and keyboard to continue work.
---

What we want to achieve - by any means possible - is to be able to view N900's Maemo and ED things in "big screen" in good quality (through HDMI or DVI), using Raspberry Pi as intermedium. "Period." It require setting up correct system on Pi, and that's ok - we will probably use Pi for other means as well - but, considering proper set of script, settings etc, it should be as hassle-free to connect n900 this way, as possible (of course, after initially setting things up).

/Estel

// edit

@javispedro
do it understand correctly, that You mean that we can use x11vnc on N900, and udlfb on Raspberry Pi, connected to DVI/HDMi monitor, and that would cause usage of DisplayLink protocol, which is meant especially for high-bandwidth (like in local network), low-latency connections? sounds cool, need to test it ASAP.

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Last edited by Estel; 2012-01-16 at 19:44.

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sulu	2012-01-16 , 20:28
Posts: 915 \| Thanked: 3,209 times \| Joined on Jan 2011 @ Germany	#34

Originally Posted by Estel

The thing is, that using Raspberry Pi exclusively, You should mirror Your content from N900 (documents, photos, programs, etc). Not to mention things like Truecrypt encrypted partitions, if You work on those.

You don't need to sync all that stuff. Just mount the N900's file systems.
I'm not talking about using the Raspberry exclusively (maybe I failed to make that clear). I just think that extending the integration beyond the already available N900's connection modes isn't worth the effort since it provides no further performance or usability gain.
Just stick with mass storage and/or PC suite mode like you do with any other computer. That's the best you can expect from connecting both devices. This way the N900's data will be available on the Raspberry and you can use it's DSP to show a nice and big Debian desktop on your TV.

Originally Posted by Estel

Also, for most "productivity" things, N900 MPU is *much* better - it's not a matter of raw mhz value, check SoC specification.

I know. This is why I wanted to do the computation on the N900 and only forward the display to the Raspberry. Unfortunately all ways of forwarding I know produce more overhead than the Cortex A8 would offer over the ARM 11.

Originally Posted by Estel

Raspberry Pi SoC is *really* strange thing.

It's not stranger than an Intel Core Duo compared to a Core i5. It's simply a different ARM generation.

Originally Posted by Estel

What we want to achieve - by any means possible - is to be able to view N900's Maemo and ED things in "big screen" in good quality (through HDMI or DVI), using Raspberry Pi as intermedium. "Period."

I completely agree with that. But the way I see it Maemo doesn't support such a thing because it's X forwarding is broken.
That still leaves Easy Debian. Since Debian's armel port doesn't distinguish ARMv6 from ARMv7 you'll have the same software running on both devices anyway. Sure, the N900's CPU is faster but to make use of that we'd have to propagate its display to the Raspberry. And when we do that we lose that performance advantage completely. So we can just as well use the Raspberry's CPU in the first place.

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	Estel	2012-01-16 , 20:55
	Posts: 5,028 \| Thanked: 8,613 times \| Joined on Mar 2011	#35

Sulu, mounting *every* N900's partition to Raspberry Pi (would it be possible to do it with normally running N900, i.e. same partition mounted by both Maemo and Raspberry Pi's Debian?), during runtime, or, even using backupmenu's read&write mass storage mode, seems to be another fine idea.

Ho ever, it would still require duplicating at least programs (LibreOffice, browser etc), because running them directly from N900's partitions (as installed for usage in ED chroot), would be far from "hassle-free", yes? Of course, this way we can also forget about any Maemo program (yet, as we can install Debian things on Raspberry Pi, it wouldn't be entirely ''tragic''

).

As for sharing internet connection it's no problem via USB networking. Yet, it would require already running N900 (here we went back into my question about 2 OS mounting the same partition, simultaneously). Thus, we would be able to share both WiFi and Cellular connections, at the same time sharing partitions, without additional overhead (Raspberry Pi read things from N900's partition via USB, and at the same time, N900 share network via USB networking).

/Estel

// Edit

Wouldn't mass-storage mode and USB-networking exclude each other? If yes, we would need to stay on USB networking, and mount N900's partitions over network, while still having possibility to share internet connection. Also, isn't creating loop devices a solution to "2 OS mounting the same partition" possible problem? N900 would have partitions mounted normally, and Raspberry Pi via a loop.

Last edited by Estel; 2012-01-16 at 21:00.

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sulu	2012-01-16 , 22:38
Posts: 915 \| Thanked: 3,209 times \| Joined on Jan 2011 @ Germany	#36

Originally Posted by Estel

Sulu, mounting *every* N900's partition to Raspberry Pi (would it be possible to do it with normally running N900, i.e. same partition mounted by both Maemo and Raspberry Pi's Debian?), during runtime, or, even using backupmenu's read&write mass storage mode, seems to be another fine idea.

That's absolutely no problem. The easiest way to do this is to use sshfs.

Originally Posted by Estel

Ho ever, it would still require duplicating at least programs (LibreOffice, browser etc), because running them directly from N900's partitions (as installed for usage in ED chroot), would be far from "hassle-free", yes?

Well at least it would be possible. Doing it for the first time it would require some effort (mounting the remote bin and lib directories, maybe redefine the $PATH variable) but it's a common technique in every centralized unixoid network system.
However I think the easier and more robust idea in this case would actually be to duplicate the software which, at least between ED and the Raspberry, would be very easy since they have the same architecture. So either way would be fine.

Originally Posted by Estel

Of course, this way we can also forget about any Maemo program (yet, as we can install Debian things on Raspberry Pi, it wouldn't be entirely ''tragic'' ).

I'm not sure if we can run Maemo software under a Debian installation on the Raspberry. If there is a way it should also work under ED in some sort of "reverse debbie" because the principles we need would be the same. So if anybody has an idea of how to do that we can start testing right away.

Originally Posted by Estel

As for sharing internet connection it's no problem via USB networking. Yet, it would require already running N900 (here we went back into my question about 2 OS mounting the same partition, simultaneously). Thus, we would be able to share both WiFi and Cellular connections, at the same time sharing partitions, without additional overhead (Raspberry Pi read things from N900's partition via USB, and at the same time, N900 share network via USB networking).

If we connect the N900 to the Raspberry in PC suite mode so that we can access the N900's WLAN and cellular interfaces we also have a network connection betwen the N900 and the Raspberry which allows us to mount the N900's filesystems on the Raspberry via sshfs.

Originally Posted by Estel

Wouldn't mass-storage mode and USB-networking exclude each other?

Yes they do but it doesn't matter since we simply replace the mass storage connection with a network connection.

Originally Posted by Estel

Also, isn't creating loop devices a solution to "2 OS mounting the same partition" possible problem? N900 would have partitions mounted normally, and Raspberry Pi via a loop.

If we'd actually do that via loop devices with write permissions on both sides that might be a problem. Be we don't use loop devices, we use network shares just like you might know them from Windows networks.

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	Estel	2012-01-16 , 23:31
	Posts: 5,028 \| Thanked: 8,613 times \| Joined on Mar 2011	#37

Sounds brilliant. Can't wait to test it - it seems, that we have so many routes to go, that we can use sulu's (which sound like most-efficient to me) approach for everyday use, javispedro DisplayLink when we *really* need Maemo programs (yet, this is just 800x480 stretched - anyway, better than tv-out...), and even experiment on more things, like ''reverse debbie'' concept (nice name, btw

) for expanding further.

/Estel

// Edit
Updated first post. By the way, Sulu, are You sure that "PC Suite" mode allows us to not only use N900's cellular, but also WiFi? As for the latter, I always though that programs like QtMobileHotspot (see repositories, it's working flawlessly) are needed, + USB Networking or tethering via WiFi (QtMobileHotspot can do both).

Of course, in any case, it's no problem, because - as You've said - we can use only USB Networking, then share partitions via sshfs (AIUI).

Last edited by Estel; 2012-01-16 at 23:47.

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rotoflex	2012-01-17 , 03:18
Posts: 569 \| Thanked: 462 times \| Joined on Jul 2010 @ USA	#38

Originally Posted by sulu

But the way I see it Maemo doesn't support such a thing because it's X forwarding is broken.

This has been a roadblock since I got my N900.

Would a good intermediate step be to ask the CSSU team to investigate standard X forwarding for the N900 for an update?

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sulu	2012-01-17 , 08:00
Posts: 915 \| Thanked: 3,209 times \| Joined on Jan 2011 @ Germany	#39

Originally Posted by Estel

By the way, Sulu, are You sure that "PC Suite" mode allows us to not only use N900's cellular, but also WiFi?

According to this blog entry it is possible:
http://myn900.wordpress.com/2010/08/...ction-via-usb/

Once you have that set up (actually steps 2-4) you can also mount the N900's file systems from the other computer via sshfs.

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freemangordon	2012-01-17 , 08:59
Posts: 3,074 \| Thanked: 12,964 times \| Joined on Mar 2010 @ Sofia,Bulgaria	#40

Guys, what is the problem with export DISPLAY=a.b.c.d:0.0 ? Excluding the fact that Maemo apps are hildonized and don't cooperate much with external WMs, the stuff works (at least here I am able to run osso-xterm on Cygwin X server)