Raspberry Pi - Hardware Flaws and Fixups?

Not  a flaw, but I'd like to know if in future it'll be possible to power more demanding usb2 peripherics from the onboard hub, having the right power source; I'm referring to a RPF blog entry where protections on power input were discussed.

My interest would be the possibility of plugging a 2,5 harddrive, and have it powered directly by the RPi, without the use of an hub; right now this is not possible, since the spinup currents would fry the tracks, 500mA max if I remeber it right, where a spinup is >1A.

Is this feasible? Sure it's more for non-educational users, but it'll be a nice plus.

Unrelated question: I read that the usb and the lan share bw, is that true? If it is, can you give some details about how that is managed? Like usb attainable speed, lan attainable speed, both combined...

Thanks.

piovrauze wrote:

Unrelated question: I read that the usb and the lan share bw, is that true? If it is, can you give some details about how that is managed? Like usb attainable speed, lan attainable speed, both combined...

Thanks.

The SOC chip is meant to be used  inside a phone. So whereas modern CPUs have high speed busses to connect to peripherals either on the motherboard or on expansion cards, that simply isn't going to happen for a chip inside a phone or tablet.

So the SOC has... USB. The model B has an USB-ethernet dongle integrated on the board. And because there is just one USB port on the chip, there needs to be an USB hub on the board as well.

Roger Wolff wrote:

The SOC chip is meant to be used  inside a phone.

 

The BCM2835 SoC wasn't developed for use inside a phone, at least not as a primary target.  Not many phones have an HDMI socket.

Broadcom describes the target applications clearly here: http://www.broadcom.com/products/BCM2835

• High Definition 1080p Embedded Multimedia Applications Processor
• The BCM2835 is a cost-optimized, full HD, multimedia applications processor for advanced mobile and embedded applications that require the highest levels of multimedia performance. Designed and optimized for power efficiency, BCM2835 uses Broadcom's VideoCore IV technology to enable applications in media playback, imaging, camcorder, streaming media, graphics and 3D gaming.

In other words,  applications like the Roku 2 media player which uses the BCM2835, of which Roku has sold 4+ million now.  The "advanced mobile" probably refers to the "camcorder" in their description, although I'm sure they're not ruling out mobile gaming devices too which connect to HDMI TVs, but probably not tablets because the 700MHz ARM1176JZF-S is rather weak compared to the 1+ GHz Cortex-A8/9 of almost all modern tablets. "Phone" is really quite a long shot, and isn't even hinted at by Broadcom.

Morgaine.

Roger Wolff wrote:

The SOC chip is meant to be used  inside a phone.

 

The BCM2835 SoC wasn't developed for use inside a phone, at least not as a primary target.  Not many phones have an HDMI socket.

Broadcom describes the target applications clearly here: http://www.broadcom.com/products/BCM2835

• High Definition 1080p Embedded Multimedia Applications Processor
• The BCM2835 is a cost-optimized, full HD, multimedia applications processor for advanced mobile and embedded applications that require the highest levels of multimedia performance. Designed and optimized for power efficiency, BCM2835 uses Broadcom's VideoCore IV technology to enable applications in media playback, imaging, camcorder, streaming media, graphics and 3D gaming.

In other words,  applications like the Roku 2 media player which uses the BCM2835, of which Roku has sold 4+ million now.  The "advanced mobile" probably refers to the "camcorder" in their description, although I'm sure they're not ruling out mobile gaming devices too which connect to HDMI TVs, but probably not tablets because the 700MHz ARM1176JZF-S is rather weak compared to the 1+ GHz Cortex-A8/9 of almost all modern tablets. "Phone" is really quite a long shot, and isn't even hinted at by Broadcom.

Morgaine.

Morgaine Dinova wrote:

The BCM2835 SoC wasn't developed for use inside a phone, at least not as a primary target.  Not many phones have an HDMI socket.

 

You could say that when I said "phone" I meant "a low power hand-held device". However:

This is the sort of phone I was thinking about: http://www.phonearena.com/news/Samsung-Galaxy-S-II-supports-HDMI-out-after-all-and-can-have-live-TV-streamed-to-it_id17004

The reason the BCM2835 is affordable is that they are powering smartphones. That makes the market large -> large volume and competitive market.

Roger Wolff wrote:

 

Morgaine Dinova wrote:

The BCM2835 SoC wasn't developed for use inside a phone, at least not as a primary target.  Not many phones have an HDMI socket.

 

You could say that when I said "phone" I meant "a low power hand-held device". However:

 

This is the sort of phone I was thinking about: http://www.phonearena.com/news/Samsung-Galaxy-S-II-supports-HDMI-out-after-all-and-can-have-live-TV-streamed-to-it_id17004

 

 

The reason the BCM2835 is affordable is that they are powering smartphones. That makes the market large -> large volume and competitive market.

I'm glad you replied to that, since I was about to reply that my own phone, the HTC Evo ("4G") uses an HDMI out port, as do many other mobile phones today.  Don't even get me started on HDMI out via USB dongle.  Or Component vs HDMI vs SDI

I believe most phones use a Cortex processor rather than an ARMv11 these days...

But at any rate the low power requirement itself is your biggest clue to it's potential applications:  With today's huge wireless data use and monolithic screen sizes the GPU is rarely any phone's biggest energy hog.  From my experience with Roku boxes (which I find unwatchable) the Broadcom 2835 is an affordable and reliable chip as long as you aren't trying to push 720p through a 450kbps mp4 stream.

Note that this "hdmi through USB" is probably not proper use of the USB connector. They need have the USB connector anyway so they multiplex the HDMI signals onto that connector when you connect that special cable. USB isn't fast enough to handle most screens. (Full-HD is about 3Gbit/sec, just a tad over 480Mbps... )

The topic was the target applications for which Broadcom designed the BCM2835, so it's not very relevant to mention the few  smartphones that *DO* have an HDMI socket when there are none that use the BCM2835.

The Samsung Galaxy SII uses a 1.2 GHz dual-core ARM Cortex-A9 SoC in most jurisdictions; the Samsung Exynos GT-I9100, a real beast of a modern ARM processor, and not the BCM2835.  A smartphone using the BCM2835 would not make it in the current smartphone market, whereas in the intended applications which Broadcom has described --- http://www.broadcom.com/products/BCM2835 --- it's perfectly fine even today since they require no huge amount of CPU power.

The full story is given here in the section labelled "VideoCore ICs" -- https://en.wikipedia.org/wiki/VideoCore

As you can see from the table, the older BCM27xx VideoCore ICs were used in iPods and Symbian phones, but no BCM28xx ever was.  The BCM2835 device is only known to have been used in Roku 2 and now in Raspberry Pi, and was not designed for smartphones.  If it had been, Broadcom's description would say so.  It doesn't.