nghia
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 9:15 am

Hi,

I read that there is currently no USB device port on the R-Pi.

But does the BCM2835 has one? If so, any possibility to bring it out on a connector?

Thanks
Nghia

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RobinJ
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 9:37 am

I read that there is currently no USB device port on the R-Pi.
You read it wrong.
Model A currently has one USB port.
Model B currently has two.
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 10:01 am

Quote from RobinJ on August 30, 2011, 10:37
I read that there is currently no USB device port on the R-Pi.
You read it wrong.
Model A currently has one USB port.
Model B currently has two.
Indeed, Model A does not have the Ethernet Port

nghia
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 8:37 pm

So does Model B has : 1 USB Host port AND 1 USB device port, correct?

If so, could the board be power supplied via the USB device port?

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liz
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 8:42 pm

Both models will have 2 host ports. You won't be able to power either via USB.
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Thorn
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 8:59 pm

Quote from liz on August 30, 2011, 21:42
Both models will have 2 host ports. You won't be able to power either via USB.

The Model A has two ports now?

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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 9:00 pm

It always did - you'll need to be able to plug a mouse and a keyboard into it!
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Michael
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 9:11 pm

So the BCM2835 provides 2xUSB? Which leads to the question, will the 'spare' 3rd USB port be available via a header on the Model-B? Also, IIRC Eben said the BCM2835 is in theory able to operate USB in host or device mode, but that is not currently exposed through software. Presumably it can do that independently on each port?

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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 9:20 pm

I'm checking for you now - I was positive there were 2, but now I think about it, the hub has to come from ethernet - and of course there's no ethernet on the Model A. It'll be a couple of hours before I can confirm that, which is super-aggravating.

Afraid I don't know about the software on board, so I can't help you with device mode.
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frafra
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 9:37 pm

If the Raspberry goes with 6-20 V, how could be possible that the BCM2835 could use an usb port as host, if usb power is 5 V? I'm a bit confused, and I would really like to power the RaspberryPi pc using the usb port :)

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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 9:38 pm

http://www.raspberrypi.org/?p=.....8#comments

Eben Upton:
"The USB hub and Ethernet functions are provided by the same chip. The cheaper board has one USB host port, while the more expensive one has two USB host ports and Ethernet. ..."

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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 10:18 pm

From what I've understood from all the discussions is that the Model A doesn't have the LAN9512 at all, BUT the ARM chip itself can support a single USB port (think cell phone guys ;) ). While the Model B has the LAN9512 which uses a USB hub to provide an ethernet port (which make the ethernet port a USB to Ethernet adapter if you think about it) and 2 USB ports)

I'm fairly confident that the ARM doesn't have the ability to provide 2 USB ports.... :?
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 10:28 pm

Yup - it appears it's my mistake, and there's only one. That's inexcusable (the mistake, I mean; I'm meant to know about this stuff); I think I now understand why Mooncake, the official Raspberry Pi cat, decided to take a chunk out of my ankle while I was writing that post earlier. She's smarter than she sounds.
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Michael
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 10:37 pm

Hey, don't beat yourself up about it. There is so much going on with this project and I'm sure there are masses of the little details changing on a day-by-day basis that you are protecting us all from - not to mention that like all (most?) of us, you have a demanding day job to do also.

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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 10:42 pm

I am the queen of multitasking. I'm pretty lucky in that I'm freelance and have a home office, so I don't have a boss standing over my shoulder and complaining about how much time I'm spending on this website!
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Re: USB Device port on R-Pi / BCM2835

Tue Aug 30, 2011 10:54 pm

The BCM2835 only supports one host USB 2.0 port itself, That is all the Model A has on it. You will have to use a hub to get more ports.

The Model B has the LAN9512. The LAN9512 gives you (2) USB 2.0 ports and (1) 10/100 Ethernet port. The software at launch only supports host mode. As abishur stated the Ethernet comes off of the LAN9512 which is a USB hub, so the Ethernet is basically a USB dongle.
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Re: USB Device port on R-Pi / BCM2835

Wed Aug 31, 2011 12:51 am

Quote from Lob0426 on August 30, 2011, 23:54
The BCM2835 only supports one host USB 2.0 port itself, That is all the Model A has on it. You will have to use a hub to get more ports.

The Model B has the LAN9512. The LAN9512 gives you (2) USB 2.0 ports and (1) 10/100 Ethernet port. The software at launch only supports host mode. As abishur stated the Ethernet comes off of the LAN9512 which is a USB hub, so the Ethernet is basically a USB dongle.

Interesting, so the model b has an unused usb port ? Couldn't it be given through headers ?

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Re: USB Device port on R-Pi / BCM2835

Wed Aug 31, 2011 1:06 am

Interesting, so the model b has an unused usb port ? Couldn't it be given through headers ?

Not sure what Your getting at here it has 2 usb ports brought to the edge of the board. Or are You asking Them to design and build a board just for You?

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Re: USB Device port on R-Pi / BCM2835

Wed Aug 31, 2011 1:52 am

He is talking about the USB host port built into the processor itself. They probably do not connect it at all when they have the LAN9512 onboard. The Model A board is going to be very different than the Model B board, at least when you look at the traces. Since the memory package is on top of the processor you probably can not reach the processor itself to make a connection to the proper pins.

Somebody would have to ask Eben or Gert van Loo about that.
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Re: USB Device port on R-Pi / BCM2835

Wed Aug 31, 2011 1:55 am

double post
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Re: USB Device port on R-Pi / BCM2835

Wed Aug 31, 2011 7:14 am

The BCM2835 USB port comes out on model A.
On Model B it goes to the LAN9512 which has three USB ports and an Ethernet port. The LAN9512 has one slave port and two master ports. The slave port of the LAN9512 talks to the BCM2835 USB Master port. The two master ports of the LAN9512 and the Ethernet port come out. Most of this you can find in the LAN9512 data sheet.

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Re: USB Device port on R-Pi / BCM2835

Wed Aug 31, 2011 7:15 am

The LAN9512 consumes one USB port and in return provides two USB ports and one Ethernet port.

nghia
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Re: USB Device port on R-Pi / BCM2835

Wed Aug 31, 2011 7:22 am

So Model A comes out with the USB from the BCM2835.
And the SW currently only provide support for host mode for this USB, right?

But does the BCM2835 USB HW module support also device mode?
if so, is there any plan to develop SW to support the device mode also?
Note: in such case off course, no USB keyboard/mouse can be connected to the R-Pi but such USB device mode can be useful in other specific applications.

Thanks

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Re: USB Device port on R-Pi / BCM2835

Wed Aug 31, 2011 1:20 pm

Quote from Gert van Loo on August 31, 2011, 08:14
The BCM2835 USB port comes out on model A.
On Model B it goes to the LAN9512 which has three USB ports and an Ethernet port. The LAN9512 has one slave port and two master ports. The slave port of the LAN9512 talks to the BCM2835 USB Master port. The two master ports of the LAN9512 and the Ethernet port come out. Most of this you can find in the LAN9512 data sheet.


Gotcha, i just skimmed through the description on the smsc website but didn't actually checked how it connected. Gotta read the data sheet next time.

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Re: USB Device port on R-Pi / BCM2835

Thu Sep 01, 2011 3:04 am

Thanks Gert van Loo that clears it up for me, LAN9512 is a hub.
Would device mode kill the Ethernet on Model B?

Boy one answer just leads to more questions. lol. That would not be a problem on the Model A. Found references in table 3.3 2Bh (Bus powered) but it is still not not clear if the ethernet will still work. It refers to disabling ports when bus powered. In that table Bit 1 equals port one and is the Ethernet port. Table 3.4 bit 7 refers to no mopre than 100ma of downstream power but the total is not to exceed 500ma. So you have a maximum of 2.5 wats to power everything. If the Ethernet draws the max of 100ma then you only have 2 watts to play with. Gert van Loo tested the Alpha board at 2.25 watts under full load. So the Model A will work just fine in device mode. The Model B is questionable if the Alpha readings are correct. Most likely the alpha board readings are higher than a Model B will be, due the extras on the board. Still questionable whether the LAN will work or be disabled in device mode. No wonder they are mulling this whole question over. Of course there is the other option which is to use 5v through a mini USB instead of the power jack they are using currently. The iPad has a really small 10 watt power to USB wall plug that would work well. It is not cheap to buy.

Where will the questions end? probably when we have RasPi's in our hands, and then new questions will start! lol
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