Raspberry Pi - Hardware Flaws and Fixups?

Kevin - I agree, people will find limitations and probably some issues that will need a workaround.  I'm keen to get input on what people have found and what should or should not be included in future versions / revisions.

I keep saying that the roadmap of activities do not extend beyond the educational release, but we all know it's fun to consider what would be possible in the future. 

Innovation - 1 part enabling technology, 1 part funding, 100 parts dreaming what if !  If we can get the kids thinking then I'll be a happy man rather that a grumpy 'ol engineer!

Pete

Generally, the best throughput you can get out of USB 2.0 Hi-speed is about 2/3 of the signalling rate, or about 320Mb/s, half-duplex. In HDD terms, that's about 40MB/s.

Perfect, I estimated the same numbers, so now they shuld be right.

This is more than enough BW for my needs, and I just need the HW to test it live now... XD

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.

Pete, are you planing to post some schematics ?

That would be nice for your educational objecitve.

Is it against commercial agrement with your distributors ?

piovrauze wrote:

 

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.

I know you mention not using a hub, but consider this: A tiny 4-port USB hub with a 2A power supply (the norm) could power both the hard drive and the RPi (with a USB type-A to micro-B cable).  As long as the overcurrent monitor on the hub is ganged (most are, since it's cheaper), there would only be a problem with overcurrent if the total draw is more than 2A. And you'd have two extra USB ports to boot.

I understand the point, and I'll have to use a hub, still I find it more attractive to use less HW.

Would it be possible to add the 5V power source directly on the onboard usb port, in parallel wit the board supply? (using the same power source)

If I use only one of the 2 usb ports, I could do it without soldering.

Is this feasible? what happens to the rest of the RPi, does this bypass the board overcurrent protection?

PeteL has said that you can bridge the fuses. You'll be stuck with "just" the 700mA entry-fuse on the microUSB port. And as long as the total doesn't exceed that, you'll be fine.

I won't be doing this mod before Farnell has RPI's in stock for "next day delivery".

That's for sure! I won't be doing HW endangering stuff till there is a costant supply of RPi ready.

This one will be kept clean of mods, and I'll use it for testing the sw and limits of the HW.

@PeteL: I remember Arch distro "overclocks" the SoC to 800MHz, how does this affect power consumption, temperature and emissions?

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.