cjrhoades
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Re: Data through the micro usb port?

Sun Dec 11, 2011 11:04 pm

Does the micro USB port that the device recieves power from also function as a regular USB port? I'm asking because I have a LapDock for my Motorola Atrix smartphone that has a single micro USB port for power, the keyboard, and the trackpad, and a micro HDMI port for video. I'd love to use one of these little computers with it if possible.


kme
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Re: Data through the micro usb port?

Sun Dec 11, 2011 11:11 pm

No. It is a DC power-only port like most smart phones.

cjrhoades
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Re: Data through the micro usb port?

Sun Dec 11, 2011 11:16 pm

Quote from kme on December 11, 2011, 23:11
No. It is a DC power-only port like most smart phones.

What? Every phone I've ever had uses the micro USB port for both power and data.

kme
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Re: Data through the micro usb port?

Sun Dec 11, 2011 11:25 pm

OK, but on the R-Pi it is DC-only. Just have at look at the PCB on the front page and that is clear.

cjrhoades
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Re: Data through the micro usb port?

Sun Dec 11, 2011 11:33 pm

Hmm, that's unfortunate. Guess I won't be able to power it from the LapDock then.

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liz
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Re: Data through the micro usb port?

Sun Dec 11, 2011 11:55 pm

Afraid not. We settled on USB power for a number of reasons, top of which was cost; but we were aware when we made that decision that some people would look at the port and assume that it was also for data, and not understand why it wasn't. For a technical look at why we went the way we did, I'd recommend Eben's post on the blog from back in October - enjoy!
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cjrhoades
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Re: Data through the micro usb port?

Mon Dec 12, 2011 12:17 am

Quote from liz on December 11, 2011, 23:55
Afraid not. We settled on USB power for a number of reasons, top of which was cost; but we were aware when we made that decision that some people would look at the port and assume that it was also for data, and not understand why it wasn't. For a technical look at why we went the way we did, I'd recommend Eben's post on the blog from back in October - enjoy!

Is there any chance that in the future, the USB power port will also be used for data? Also, I'm wondering if this would work:

obarthelemy
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Re: Data through the micro usb port?

Mon Dec 12, 2011 12:36 am

i don't think the hub will accept incoming power from one of its device connexions.
I also don't know if the lapdock is smart enough to switch USB power off when connected to a powered hub.
you might get by with a custom cable that takes power from the lapdock to the Pi, and data lines from the same lapdock port to the hub ?
i'm sre people who know better than i do will chime in ^^

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abishur
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Re: Data through the micro usb port?

Mon Dec 12, 2011 12:40 am

Even if it was a data port too (which to re-iterate it's only uses the micro-usb form fact to take advantage of it's power standards and its universal availability ;) ), I think that the Motorola Atrix is unique in being able to use that docking station isn't it? I think they have some proprietary software running on the phone to get it to work with docking station.
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cjrhoades
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Re: Data through the micro usb port?

Mon Dec 12, 2011 12:46 am

Quote from abishur on December 12, 2011, 00:40
Even if it was a data port too (which to re-iterate it's only uses the micro-usb form fact to take advantage of it's power standards and its universal availability ;) ), I think that the Motorola Atrix is unique in being able to use that docking station isn't it? I think they have some proprietary software running on the phone to get it to work with docking station.

The LapDock itself isn't really special in any way. It's just a dummy laptop that has an 11.5" 1366x768 HDMI display, keyboard, trackpad, and battery. When the Atrix has any HDMI cord plugged into it, it can either mirror whats on its display or fire up Webtop which is a customized (and locked down) Ubuntu 8 Linux distro. You can actually run Webtop over HDMI to a regular TV and use the display on the phone as a trackpad or use a bluetooth mouse and keyboard.

I've seen the LapDock used by itself as a display for the PS3 and other things which is why I was hoping it could be used as a mobile all in one monitor, keyboard, and mouse for RPi. It doesn't require any special software to be used and the different parts of the dock can all function separately.

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Re: Data through the micro usb port?

Mon Dec 12, 2011 1:01 am

Quote from cjrhoades on December 12, 2011, 00:17
Also, I'm wondering if this is possible:


Is there any technical information on the LapDock, like a schematic? :-) ;-)

Otherwise, here's my SWAG. Normally, you connect a USB keyboard and mouse to USB host ports, which supply power to the keyboard and mouse. If there's only one USB host port, it supplies power to a hub which then powers the keyboard and mouse. The LapDock is a little different: it must include a hub so the Atrix can talk to the LapDock's keyboard and mouse, but the LapDock's internal hub also provides upstream power to the Atrix which is the opposite of a normal upstream port. But that's OK, since both devices are made by Motorola.

Most likely what you'd need for RasPi is to make a custom cable that takes the LapDock's power signals and sends them to RasPi's power input, and takes the data twisted pair and sends it to one of RasPi's USB host ports.

If my SWAG is correct, this should work electrically and provides data communication. However, the danger with USB is always that the LapDock's internal hub may do something non-standard and the standard Linux driver on RasPi may not know how to handle it. So before you build any cables, try powering RasPi with its own power supply, and then see if a RasPi USB host port can talk to LapDock over a standard USB A to USB micro-whatever cable.

It should be OK to have RasPi and LapDock both driving the cable with +5V, since there ought to be diodes in there to prevent actual current. Personally, I'd wait until I saw the RasPi schematics (which I suspect they'll publish once the design is verified) and make sure it has a diode to prevent LapDock +5V from affecting RasPi through RasPi's USB host port. In fact, I'd mask off the +5V signal on the cable just to make sure. After all, you don't want to risk damaging either or both devices.

An alternative to the custom cable might be to hack RasPi so the USB host port's +5V goes back to the RasPi's power input. You definitely want to review the RasPi schematic before trying this.

Since this is a SWAG, no warranty is expressed or implied.

SWAG = Scientific Wild-Assed Guess, a term often used by USA consultants.

cjrhoades
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Re: Data through the micro usb port?

Mon Dec 12, 2011 1:48 am

Here's what I'm assuming about what's inside the LapDock. The internal bettery is connected to a USB hub and the display. The hub has 5 ports, one for the trackpad, keyboard, the micro USB out to the phone, and two for the USB ports in the back of the dock.

I actually completely forgot about the two rear USB ports. Motorola put those in so you could plug a mouse or flash drive into it. Since I'm assuming they're connected to the same hub as the built in keyboard and trackpad, would it be safe to assume that I could run a male to male USB cable between them and it would connect the keyboard and trackpad to the RPi? That would be much easier than making a custom cable.

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Re: Data through the micro usb port?

Mon Dec 12, 2011 1:53 am

Quote from cjrhoades on December 12, 2011, 01:48
Here's what I'm assuming about what's inside the LapDock. The internal bettery is connected to a USB hub and the display. The hub has 5 ports, one for the trackpad, keyboard, the micro USB out to the phone, and two for the USB ports in the back of the dock.

The one port for the phone is the upstream port; all the others are downstream ports. The upstream is the only one that can connect to the Pi.

cjrhoades
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Re: Data through the micro usb port?

Mon Dec 12, 2011 1:55 am

Quote from shiftyphil on December 12, 2011, 01:53
The one port for the phone is the upstream port; all the others are downstream ports. The upstream is the only one that can connect to the Pi.
Doesn't USB go both ways? Or do you know something about the LapDock internals I don't? Or maybe I don't know what I'm talking about... lol.

shiftyphil
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Re: Data through the micro usb port?

Mon Dec 12, 2011 2:06 am

Quote from cjrhoades on December 12, 2011, 01:55
Doesn't USB go both ways?

Nope.

A hub will always have one upstream; any exception is a violation of the standard.

Only "USB On-The-Go" ports can act in either direction.

cjrhoades
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Re: Data through the micro usb port?

Mon Dec 12, 2011 2:09 am

Ah, right. Well, I'll just have to wait until RPi is done, buy one, and experiment. Hopefully I won't blow anything up.

shiftyphil
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Re: Data through the micro usb port?

Mon Dec 12, 2011 2:11 am

Quote from cjrhoades on December 12, 2011, 02:09
Hopefully I won't blow anything up.

But that's the fun part!

Just make doubly sure the power is connected right; you won't do any permanent damage just getting the data wrong.

The USB side should really be very easy - there's only four wires total.
I'd be more worried about the HDMI side, and really hoping you can get that connected with off-the-shelf cables.

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Re: Data through the micro usb port?

Mon Dec 12, 2011 3:30 am

ah, so what you're saying is that the dock can have all its functions working independently via other connection methods, but only that one phone can interface directly via usb through special software... but that should mean it doesn't matter if the r-pi micro-usb port is a data port. The lapdock can still be used via other methods, and even if the port was a data port instead of just being a power port, then it still wouldn't be able to take direct advantage of the lapdock through a one port hook-up, it would still have to go the roundabout route of connecting the components up one piece at a time.
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cjrhoades
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Re: Data through the micro usb port?

Mon Dec 12, 2011 3:57 am

Quote from abishur on December 12, 2011, 03:30
ah, so what you're saying is that the dock can have all its functions working independently via other connection methods, but only that one phone can interface directly via usb through special software... but that should mean it doesn't matter if the r-pi micro-usb port is a data port. The lapdock can still be used via other methods, and even if the port was a data port instead of just being a power port, then it still wouldn't be able to take direct advantage of the lapdock through a one port hook-up, it would still have to go the roundabout route of connecting the components up one piece at a time.

Correct, the LapDock doesn't require any special hardware to be used. The one I have was made specifically for the Atrix 4g but with a bit of modding, any phone with Webtop can use it including the Bionic, Photon, and Razr.

If the micro USB power port handled data as well, you would only need one additional cable to run HDMI to the LapDock.

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Re: Data through the micro usb port?

Mon Dec 12, 2011 4:58 am

Quote from abishur on December 12, 2011, 03:30
ah, so what you're saying is that the dock can have all its functions working independently via other connection methods, but only that one phone can interface directly via usb through special software...

There's no "special software" required, looks like once you solve the connection issue everything is standard (from what I can find from other people experimenting with it).

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Re: Data through the micro usb port?

Mon Dec 12, 2011 5:55 am

Wouldn't the connection issue be the special software I'm referring to? I mean it's not like every phone automatically listens for keyboard and mouse events via usb. There's definitely a special daemon running and listening for the appropriate information (keyboard/mouse input) in the usb port. That said, I freely admit that I don't know anything about this item specifically and I'm just applying what I know about how things *like* this operate. That said, from what y'all have been saying, it doesn't matter that the micro usb port doesn't do data. You should be able to use the device by hooking it up to the r-pi's regular USB port and HDMI (with the appropriate full to micro adapters of course), right?
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shiftyphil
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Re: Data through the micro usb port?

Mon Dec 12, 2011 6:11 am

Quote from abishur on December 12, 2011, 05:55
Wouldn't the connection issue be the special software I'm referring to? I mean it's not like every phone automatically listens for keyboard and mouse events via usb. There's definitely a special daemon running and listening for the appropriate information (keyboard/mouse input) in the usb port.

For the Pi, there is no special software needed.

That said, I freely admit that I don't know anything about this item specifically and I'm just applying what I know about how things *like* this operate. That said, from what y'all have been saying, it doesn't matter that the micro usb port doesn't do data. You should be able to use the device by hooking it up to the r-pi's regular USB port and HDMI (with the appropriate full to micro adapters of course), right?

Essentially.

cjrhoades
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Re: Data through the micro usb port?

Mon Dec 12, 2011 10:31 am

Quote from abishur on December 12, 2011, 05:55
Wouldn't the connection issue be the special software I'm referring to? I mean it's not like every phone automatically listens for keyboard and mouse events via usb. There's definitely a special daemon running and listening for the appropriate information (keyboard/mouse input) in the usb port. That said, I freely admit that I don't know anything about this item specifically and I'm just applying what I know about how things *like* this operate. That said, from what y'all have been saying, it doesn't matter that the micro usb port doesn't do data. You should be able to use the device by hooking it up to the r-pi's regular USB port and HDMI (with the appropriate full to micro adapters of course), right?

The phone needs specialized software (Webtop) but nothing else does. When the phone detects a display is plugged into its micro HDMI port, it fires up Webtop which is essentially a customized Ubuntu 8 distro.. Webtop is given full control of the phones USB port so technically you could plug any USB accessory into the phone and it would work as long as you have the drivers for it. Normally that wouldn't mean much, but it's possible to hack Webtop and install a full version of Ubuntu or any other Linux distro and from there you can do much more.

Anyways, RPi should be able to make full use of all of the LapDock's features without much work.

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Re: Data through the micro usb port?

Mon Dec 12, 2011 1:41 pm

Yeah that's exactly the point I was making there :P The OP wants to know if the r-pi micro usb port could support data, and I'm saying "No, but ultimately it doesn't make a difference in relation to the lapdock" ;) (Even if it did, you'd still have to connect it piecemeal to the lapdock)
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cjrhoades
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Re: Data through the micro usb port?

Mon Dec 12, 2011 1:43 pm

Quote from abishur on December 12, 2011, 13:41
Yeah that's exactly the point I was making there :P The OP wants to know if the r-pi micro usb port could support data, and I'm saying "No, but ultimately it doesn't make a difference in relation to the lapdock" ;) (Even if it did, you'd still have to connect it piecemeal to the lapdock)

Yes, it would still require two cables. But two cables is better than four and a USB hub.

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