On a sunny day (Fri, 09 Mar 2012 13:26:09 GMT) it happened snipped-for-privacy@puntnl.niks (Nico Coesel) wrote in :
Chinese mediaplayer I have,
Oh, I forgot to mention WHY I did the separate charger... The PC USB port would switch itself off because of too much current, IIRC it is only 600mA in the spec? Not sure. If the strawberry pie is indeed 700mA that will promise a whole lot of fun on a whole lot of peesees.
Chinese mediaplayer I have,
The USB 2.0 spec only allows for 500 mA maximum current after the device has been configured. Unconfigured devices are only allowed 100 mA. For devices that require more than 100 mA, the configuration is only done after the host first reads the current requirement, and has determined that it can still supply it. For instance, a 4 port bus-powered USB hub can only support 4 devices if they have a max 100 mA requirement.
Cell phone/battery chargers with a USB type plug are not limited to those currents, and can typically supply more.
I suspect the strategy is to tell people to just go buy a cigarette lighter (12V) to micro-USB power adapter on eBay for literally a buck or two shipped to your door. (I just found one for $0.99 shipped from Taiwan, 5V @ 1A output...)
Exactly. What I'm looking for is the Embedded Linux Computer with FPGA connected directly to the CPUs bus and to 0,1" headers, so that my students could deal with different peripherals (implemented in the FPGA) and connected to simple circuits assembled on the breadboard (or on prototype PCB connected via flat cable). Does anybody knows about such cheap boards?
-- TIA & Regards, WZab
No, but keep in mind here that some Linux-capable CPUs these days are pretty fancy (caches, superscalar, etc.) and have CPU busses that are non-trivial to interface too -- it's a lot more complex than the old days of data, address, and a R/W strobe. Similarly, many CPU busses are fast enough that you might not get away with ribbon cables anymore unless you're running, e.g., every other wire as ground.
So just be careful to avoid those for your purposes. :-)
(In a modern PC, while things like PCI cards are memory-mapped, when someone writes a line of code as simple as *MyDeviceRegister =
0xdeadbeef, what actually happens is a very complex transaction between the CPU, its local bus, the north bridge, the PCI bus, and whatever chip is on the target PCI device.)
Chinese mediaplayer I have,
Sorry, but that is pure theory. In reality 99% of the PCs will happily deliver >1A through their USB port. Current regulation circuitry and controlling it adds extra costs and customers might think their PC is broken because the devices are not working or are not getting charged. Manufacturers want to avoid that extra hassle.
I just tested a USB port of my PC with a dummy load and it supplies over 1A without a device attached.
-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
Don't count on connecting a CPU bus. Those days are long gone. The speeds are too high. DDR and flash memory usually have dedicated busses. Even if you could craft something that resembles a memory bus there are many issues to work out. Especially if you would make the bus go over headers. Nowadays you'd use GPIO, I2C, SPI or USB.
-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
The only computers I've seen complaining about USB current consumption is Macs, both desktops and laptops, and running both OS X and Windows. You get this nice loop where the OS turns off the host port, pops up a warning dialog, automatically turns the host port back on, turns it back off again, pops up another dialog etc. I was still dismissing dialogs for almost a minute after yanking out the device.
-a
The Model A that is intended for classrooms does not have on-board Ethernet.
-a
Is this a hard spec or do they just say that to make it simple. I see a 3.3V regulator close to RP's power connector.
-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
What is intended and what will be bought for various curricula is different, as I have dealings with ICT/Computing teachers in UK most are actually interested in Model B not A, hard wired LAN is easier as lots of building have no wifi or wifi blackspots.
Anyway adding wifi may seem cheap until you lose opne or two a lesson and more bits to check in and out.
--
Paul Carpenter | paul@pcserviceselectronics.co.uk
PC Services
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In last two years seen at least three Win PCs complain about it.
--
Paul Carpenter | paul@pcserviceselectronics.co.uk
PC Services
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Why do you think so? E.g. in a board based on AT91SAM9G45 (
We have created such prototype a few years ago (
The idea is to have a single hardware configuration, which may be configured to have an PC working with simple bus connected peripheral or with complex Bus Mastering DMA capable peripheral, or a peripheral connected via ISI, I2S, SPI or whatever else.
-- Regards, Wojtek
Preliminary schematic of the iMX233-OLinuXino has been uploaded to GitHub.
This is very rough and will have lot of changes. These changes will possibly be uploaded on Monday.
A new user group has been set up for this board at:
This is one of two new Linux low cost boards, that will be produced by Olimex. First one has 64Mb of ram, second one will be the same CPU speed as RPi, and have 256Mb of ram.
====================== Question: Like the idea, some sort of raspberry pi. What kind of android version would be supported since it only contains 64mb ram ? incl. TV out ?
Answer: OLIMEX Ltd says: March 7, 2012 at 10:05 pm
sorry there are few projects in my mind ;) indeed 64MB memory is too low for Android, but there is another project with 256MB and different processor which is too early to announce now :) ======================
Cheers Don...
===================
-- Don McKenzie Dontronics: http://www.dontronics-shop.com/ DuinoMite the PIC32 $35 Basic Computer-MicroController http://www.dontronics-shop.com/the-maximite-computer.html Just add a VGA monitor or TV, and PS2 Keyboard. Arduino Shield, Programmed in Basic, or C.
the core runs off that regulator, the USB socket and the expansion connectors have the input power directly connected. The ethernet and the onboard USB hub may need 5V.
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No problem. A USB to ethernet converter works just as well. There is a big chance the onboard ethernet works through USB. Many SoCs don't provide a MAC because mobile devices don't need one.
-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
That device is relatively slow. IIRC about the same device is used on Conitec's Eva board.
-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
W dniu 09.03.2012 20:45, Joel Koltner pisze:
Well, I know it. In our team we've dealed with PCI and PCI-e from both sides - at PC level and at FPGA level.
However for didactic purposes it is good sometimes to let students to work with hardware, which is directly coupled to the CPU bus (like EBI in ARMs) before they start to deal with more complex buses like PCI.
-- Regards, WZab
100mA would never charge a phone. 3000mA is much better. AFAIK, they try to charge the phone at 1C.
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