dapa79
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Minor improvements for a model C

Wed Aug 08, 2012 7:08 am

I really like my Raspberry Pi and can't stop thinking about new applications for it.
There are however a few minor issues that I hope could be addressed in a model C. (or B rev.2)

USB power. The 140mA fuse is set way to low. Now almost all usb devices needs a powered USB hub. This sort of spoils the purpose
of a tiny device. The setup quickly turns into an pile of cables and boxes that takes up space and looks quite ugly.
Is the usb hub/nic IC capable of handling 500mA/port? If so can't the port polyfuses be 500mA?
If the pi itself needs ~500mA and 200 mA is used for the two usb ports that would leave an additional 2-300mA on most 1A 5V mobile chargers.

Sound. I think most people would be willing to pay a few extra dollars for a proper audio output (and perhaps input).
I can understand the cost saving aspect behind the pwm output but the sound quality is for the most part unusable. It reminds me of my old 486 with pc speaker driver.
Sure you can use a USB sound card but then you'll probably end up dealing with the problem above.
A cheap DAC with descent sound quality i think is a necessity for R-Pi. For those seeking ultimate HiFi it would be nice to have i2s on the i/o connector.

Size. Considering the fame of R-Pi I think the attention-drawing selling point of "sized as a business card" is now of less importance. A model C could be made slightly larger
to accommodate for proper mounting holes, audio DAC and a few additional I/O pins like i2s. If possible it would also be great to have at least one connector-free side.

Model ID. Hardware identification to be able to license and offer one hardware encoding codec (h264) for general use on this model (not tied to a camera module). Perhaps also the often requested license for mpeg2 decoding.

Are there other minor hardware improvements you would like to see in a hypothetical model C?

alexchamberlain
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Re: Minor improvements for a model C

Wed Aug 08, 2012 7:36 am

dapa79 wrote:USB power. The 140mA fuse is set way to low. Now almost all usb devices needs a powered USB hub. This sort of spoils the purpose
of a tiny device. The setup quickly turns into an pile of cables and boxes that takes up space and looks quite ugly.
Is the usb hub/nic IC capable of handling 500mA/port? If so can't the port polyfuses be 500mA?
If the pi itself needs ~500mA and 200 mA is used for the two usb ports that would leave an additional 2-300mA on most 1A 5V mobile chargers.
In defense of the Foundation, this is the spec. It says that USB ports should supply 140mA unless the device negotiates more. My solution to this would be for someone (maybe even the Foundation, but Iknow the guys there are very busy) to develop a powered USB hub expansion board to cut down on some of the faff.
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dapa79
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Re: Minor improvements for a model C

Wed Aug 08, 2012 8:48 am

Yes, but as discussed in http://www.raspberrypi.org/phpBB3/viewtopic.php?t=5830, it seems that the current polyfuse model can produce out-of-spec voltages, something needs to be done about those fuses anyways. Wouldn't it be possible to stretch the specs to accepting 500mA devices even if that amount of current cannot be supplied in all cases? With a 1A charger there could be enough to supply one port with 500mA if the other one is not used. Is there a risk of permanent damage if the host cannot supply the full 500mA to the peripheral?

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Re: Minor improvements for a model C

Wed Aug 08, 2012 10:30 am

The polyfuse issue is being looked in to.
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Re: Minor improvements for a model C

Wed Aug 08, 2012 3:53 pm

Some time back I suggested developing a board the same size as the Pi PCB to contain a powered USB hub, power supply (for itself and the Pi) with a power switch,and--optionally--a couple of other things, like an active HDMI-to-VGA subsystem. The idea would be to then design a case that stacked the two boards and have short jumper cables to connect the two.

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Re: Minor improvements for a model C

Wed Aug 08, 2012 4:00 pm

W. H. Heydt wrote:Some time back I suggested developing a board the same size as the Pi PCB to contain a powered USB hub, power supply (for itself and the Pi) with a power switch,and--optionally--a couple of other things, like an active HDMI-to-VGA subsystem. The idea would be to then design a case that stacked the two boards and have short jumper cables to connect the two.
+1 (except the HDMI-to-VGA stuff)
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Re: Minor improvements for a model C

Wed Aug 08, 2012 4:23 pm

alexchamberlain wrote:
W. H. Heydt wrote:Some time back I suggested developing a board the same size as the Pi PCB to contain a powered USB hub, power supply (for itself and the Pi) with a power switch,and--optionally--a couple of other things, like an active HDMI-to-VGA subsystem. The idea would be to then design a case that stacked the two boards and have short jumper cables to connect the two.
+1 (except the HDMI-to-VGA stuff)
Why not?
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Re: Minor improvements for a model C

Wed Aug 08, 2012 4:25 pm

I'd say have a 2nd USB channel ...
and another NIC
and the connectors all on one side
and an electric pony
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Re: Minor improvements for a model C

Wed Aug 08, 2012 5:08 pm

Only one pony? :o
Noob is not derogatory the noob is just the lower end of the noob--geek spectrum being a noob is just your first step towards being an uber-geek ;)

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Re: Minor improvements for a model C

Wed Aug 08, 2012 5:23 pm

Umm, difficult to say.

Some analog inputs on the GPIO.
A DC filter on the sound out.
A VGA set of holes on the board.

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Re: Minor improvements for a model C

Wed Aug 08, 2012 7:03 pm

Holes, holes, holes, holes - that's 4 holes - one in each corner.

And perhaps the posibility of expanding the memory, although I accept that that might go against the whole definition of a 'System on a Chip'.

Despite that I'm impressed with what the foundation has acheived - most of the improvements I would like to see are software ones and these are emerging....

dapa79
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Re: Minor improvements for a model C

Wed Aug 08, 2012 8:02 pm

Joe Schmoe wrote:
alexchamberlain wrote: +1 (except the HDMI-to-VGA stuff)
Why not?
The SoC has no native VGA support and I think the required IC was quite expencive.

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Re: Minor improvements for a model C

Wed Aug 08, 2012 9:54 pm

dapa79 wrote:
Joe Schmoe wrote:
alexchamberlain wrote: +1 (except the HDMI-to-VGA stuff)
Why not?
The SoC has no native VGA support and I think the required IC was quite expencive.
That's possible, but by not means certain. The Neewer adapter sells for about $15. It does appear to have a limited range of resolutions it will support though--works perfectly "out of the box" with my 1920x1080 display, but I couldn't find a way to persuade it to work at all with a 1280x1024 display. On the other hand the not quite $40 standalone converter I got from Monoprice works great with every monitor I've tried it with. Of course the Monoprice on comes in a metal case and has a separate power supply and LED status lights (it also breaks out the audio stream to a pair of RCA jacks), so there's a lot more hardware there.

My guess would be that adding a VGA adapter to a board being built to do the rest of the stuff shouldn't add more than $5 to $10 to the parts cost for a *good* converter chip.

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Re: Minor improvements for a model C

Wed Aug 08, 2012 11:31 pm

"Simple" ideas from me most of this is not expensive in production.

Power (and USB)
Change connector to use a fairly standard 5V @ 2 to 2.5A PSU from USB powered hub, leaving headroom to power USB sockets at 500mA each as per USB 2 spec.

Mounting Holes at least 3 mounting holes for stacking boards and/or casing. Most educational users will find they need to screw down or case the boards for easier handling by children and making it easier to tie down cables so part don't go 'missing' at ends of lessons. When mice had roller balls at all sorts of schools the balls would disappear. Other bits go 'missing'.

The VGA problem
Even if not room for VGA converter chip add row of pin headers behind HDMI connector to allow a piggy-back VGA converter board, (must support up to a minimum resolution of 1240 x 1028)

GPIO Connector
Change from pin header to standard connector that uses the polarisation bump as on IDC ribbon cables. When using with children and people who are new to adding their own circuits avoids problems with connectors off by one pin or row, or even back to front. With a class of 10-30 children some will do it accidentally, some deliberately especially if used in a core curriculum lesson.

GPIO Signals
My main problems with I/O is
a) Default of only 7 bit parallel I/O not accessible easily as byte wide read and writes from most languages.
b) Byte wide port with two extra signals for driver to support a read and write strobe for easier interfacing
c) Layout of GPIO pins Serial interfaces on one side of connector, parallel data on other side for easier wiring by novices.
d) Dedicated input for ONE Interupt (low level or falling edge) that is supported by drivers to a pre-registered call back function in user code, closing driver resets to ignore int, no function registered is ignored. Easy switch interfacing and teaching of interrupts to children (up to 18 years old) without having to do low level or kernel programming.
e) REMOVE 3V3 from GPIO so no power taken from it.

GPIO software
As one iof the main reasons for educational use is ability to write software to talk to outside world and get children used to multi tasking operating systems, so everything should be easily coinfigurable in userland. No sudo by children. Most children will expect to use this from windows not command prompt.

Please dont say this is not possible, as you do not have to go sudo to run programmes that access other I/O like serial ports and file I/O. The Userland to devices bridge needs to be there to be worthwhile for all GPIO functions. No fancy export or other such tricks that uber geeks use, we are talking about novice and often dis-interested users.
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Re: Minor improvements for a model C

Thu Aug 09, 2012 12:59 am

I'll throw my hat in the pot (hey, if I am to be disruptive here...) and:

* I recently discovered that ethernet is running through a USB bridge of sorts -- considering that USB has been *purposely designed* by Intel to be as inefficient / processor-heavy as possible, would there be a better way to re-implement ethernet connectivity?

* I also discovered that the few chips on the PCB (the SoC, ethernet/USB, voltage regulator (?!)) can get quite hot, bringing upon the emergence of a heatsink after-market (e-bay, tindie, etc.), with some people even putting *fans* on their pi enclosures! I'd recommend the foundation looking into having future Raspberry Pi's (sic) being outfitted with heatsinks to avoid premature deaths by over-heating.

* I have noticed some have been modifying the on-board power-related circuitry to improve efficiency and whatnot. Maybe the foundation should look into this, to see what issue(s) is(are) being addressed and modify the Pi's design accordingly.

* Of course, a "model c" should have hardware-based MPEG-2 decoding activated.

* Lastly, it would not hurt if there was a way to double the system's RAM. I'm sure XBMC/OpenELEC could fare much better with more elbow room.

...Oh, one more thing: I honestly cannot remember the last time I have seen a composite monitor. Really. That connector could be dropped and replaced by something that could be more useful, like a 2nd pair of USB connector... or a S/PDIF connector to complement the existing audio-out?

I know most of this could end up making a "model C" Pi more expensive, but I cannot fathom it being dramatically so. And since the "model B" is already more expensive than the "model A", then what's wrong with making the "model C" cost more than the "B"?

Cheers.

P.S.: a real-time clock might be something to consider. NTP servers are not always available.

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Re: Minor improvements for a model C

Thu Aug 09, 2012 1:26 am

Eight cores. Really ... this is 2012 already. 4-cores are now out there with huge specs and much cheaper than 4xRPi (ODROID-X @ £86 vs 4 x £25.92 , also 4x1.4ghz&1mbL2 ... same 1080p BTW)
Real Time Clock ... use a standard CMOS battery mounted 90 degrees to the 'board
Mounting holes ... please!

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Re: Minor improvements for a model C

Thu Aug 09, 2012 5:51 am

jb1963 wrote:I'll throw my hat in the pot (hey, if I am to be disruptive here...) and:

* I recently discovered that ethernet is running through a USB bridge of sorts -- considering that USB has been *purposely designed* by Intel to be as inefficient / processor-heavy as possible, would there be a better way to re-implement ethernet connectivity?
That kind of depends... How efficient is the USB+Ethernet chip? Alternatively, how good a version of such a chip could be used as a replacement without serious cost?
* I also discovered that the few chips on the PCB (the SoC, ethernet/USB, voltage regulator (?!)) can get quite hot, bringing upon the emergence of a heatsink after-market (e-bay, tindie, etc.), with some people even putting *fans* on their pi enclosures! I'd recommend the foundation looking into having future Raspberry Pi's (sic) being outfitted with heatsinks to avoid premature deaths by over-heating.
You've just named pretty much all the active chips on the Pi...
* I have noticed some have been modifying the on-board power-related circuitry to improve efficiency and whatnot. Maybe the foundation should look into this, to see what issue(s) is(are) being addressed and modify the Pi's design accordingly.
Again...it's a cost issue. Would I like to see better power regulators? Sure...but how much would it add to the cost of the boards?
* Of course, a "model c" should have hardware-based MPEG-2 decoding activated.
One could argue about that.... Yes, I know there are people that really, really want MPEG-2. But can the cost adding it be justified within the pricing envelope for the purpose for which the Pi was developed? Now if you're willing wait a couple of years, one plot that was posted showed a large proportion of the controlling patents expiring...and that might open the door to adding this feature for a lot less money.
* Lastly, it would not hurt if there was a way to double the system's RAM. I'm sure XBMC/OpenELEC could fare much better with more elbow room.
It has been noted that the current processor could us a 512MB memory package. At present, it's the same issue: cost. It's my personal opinion that the price of the 512MB unit will probably go down and the cost will be where the 256MB package is now...making the switch feasible. And, if I'm not too much mistaken, no board redesign would be required.
...Oh, one more thing: I honestly cannot remember the last time I have seen a composite monitor. Really. That connector could be dropped and replaced by something that could be more useful, like a 2nd pair of USB connector... or a S/PDIF connector to complement the existing audio-out?
Composite still exists in older TVs...and they can be used as monitors. In time, that will go away...but the equipment will linger a lot longer than you think. Years at least, and quite possibly decades into the future.

In spite of that, I agree that dropping the composite video out is not unreasonable. What I'd expect to be added in place of it would be audio in, though. For a second pair of USB connectors (even assuming there is room, which I'm inclined to doubt), I don't know if the chip that's handling the ones we've got could even do 2 more. Then there's the power issue that would come with them....
I know most of this could end up making a "model C" Pi more expensive, but I cannot fathom it being dramatically so. And since the "model B" is already more expensive than the "model A", then what's wrong with making the "model C" cost more than the "B"?
Nothing intrinsically wrong with another model that costs more. However, rather that adding some of things you're proposing, I'd rather see a modest increase in power budget. Say, bringing the total power envelope to 1A (from 700mA) to provide a bit more power for the USB ports and generally a bit better margin to handle loads.
P.S.: a real-time clock might be something to consider. NTP servers are not always available.
That would be a nice option. As I understand it, the biggest issue is...where to you put the battery? However, if there were a set of pins to attach a separately purchased clock daughter card, it might be possible.

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Re: Minor improvements for a model C

Thu Aug 09, 2012 6:36 am

W. H. Heydt wrote:However, if there were a set of pins to attach a separately purchased clock daughter card, it might be possible.
Erm... there are. There exists both the pins (GPIO) and the daughter boards...
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Re: Minor improvements for a model C

Thu Aug 09, 2012 9:05 am

All of the items requested cost money. There is a reason the Raspi is cheap - it doesn't have all those extra bells and whistles. The lists above would get close to doubling the cost.

One error point from above - there is no need for heatsinks. At all. There will be no deaths from overheating without them.
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dapa79
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Re: Minor improvements for a model C

Thu Aug 09, 2012 9:39 am

Ray_GTI-R wrote:Eight cores. Really ... this is 2012 already. 4-cores are now out there with huge specs and much cheaper than 4xRPi (ODROID-X @ £86 vs 4 x £25.92 , also 4x1.4ghz&1mbL2 ... same 1080p BTW)
Real Time Clock ... use a standard CMOS battery mounted 90 degrees to the 'board
Mounting holes ... please!
Please keep this thread to minor changes. A different CPU/GPU would be a completely different product. More powerful boards already exists but at a different price level. (like Odroid-x).

dapa79
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Re: Minor improvements for a model C

Thu Aug 09, 2012 9:55 am

jamesh wrote:The polyfuse issue is being looked in to.
Great!!

Do you know if there has been any discussion about the analog sound? USB sound cards, sold for as little as £1.50 inc. shipping on ebay, do take up space as well as a valuable USB port. It would be great if the build in audio could be improved. I suspect it wouldn't add many cents to the cost considering the price mentioned above.

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Re: Minor improvements for a model C

Thu Aug 09, 2012 10:43 am

dapa79 wrote:
jamesh wrote:The polyfuse issue is being looked in to.
Great!!

Do you know if there has been any discussion about the analog sound? USB sound cards, sold for as little as £1.50 inc. shipping on ebay, do take up space as well as a valuable USB port. It would be great if the build in audio could be improved. I suspect it wouldn't add many cents to the cost considering the price mentioned above.
No plans I'm afraid (in fact there are very few plans for HW changes at all - only to fix any issues found).

It's not just a question of a $1 part- there is the board redesign, board conformance would need to be redone, drivers to be written etc. Not worth it for such a change.
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Re: Minor improvements for a model C

Thu Aug 09, 2012 11:11 am

W. H. Heydt wrote:Some time back I suggested developing a board the same size as the Pi PCB to contain a powered USB hub, power supply (for itself and the Pi) with a power switch,and--optionally--a couple of other things, like an active HDMI-to-VGA subsystem. The idea would be to then design a case that stacked the two boards and have short jumper cables to connect the two.
Yes this would be intresting to get the pi out to more pepole. As it's now pepole need to by a tv or a new screen but if the have a vga connetor the pi can get to more pepole.
And a newer ARM procersor would be nice and more ram

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Re: Minor improvements for a model C

Thu Aug 09, 2012 7:35 pm

bastian94 wrote:
W. H. Heydt wrote:Some time back I suggested developing a board the same size as the Pi PCB to contain a powered USB hub, power supply (for itself and the Pi) with a power switch,and--optionally--a couple of other things, like an active HDMI-to-VGA subsystem. The idea would be to then design a case that stacked the two boards and have short jumper cables to connect the two.
Yes this would be intresting to get the pi out to more pepole. As it's now pepole need to by a tv or a new screen but if the have a vga connetor the pi can get to more pepole.
And a newer ARM procersor would be nice and more ram
The proposal was for a "support board" with the same form factor as the Pi, and would--thus--be entirely optional. A newer ARM processor, unless one that is pin-compatible with the current one, would mean a board redesign. More memory...by all accounts, it is possible--at least in theory--to manufacture Pis with a 512MB memory unit.

I can think of one exception that is likely to be possible in the way of a "better" processor chip. That would be ones rated for a higher clock frequency. Over time, a shift to one rated at 1GHz is, I think, fairly likely.

So on the whole minor mods for a version "C" (and assuming no board redesign), I think the limits would be 512MB RAM, 1 GHz processor, and *maybe* more power allowed on the USB ports (i.e. higher current permitted through the polyfuses).

Edit to add... I see the Odroid-x as a server, compared to the Pi as a PC. The thing I'd like to see would be if Raspbian, or a minor variant of it, would run the Odriod-x, but I don't think there is a sufficiently large community there to do the needed work (though I could be wrong).

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Re: Minor improvements for a model C

Thu Aug 09, 2012 8:34 pm

You can usually overclock to at least 850-900 and overvolt to 1GHz fairly reliably. There has been some consideration to actually upping the allowed spec (i.e. setting the standard at 800 or more) as the SoC has proved so reliable at these higher speeds. Will depend on more testing/reliability reports I guess.
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