Raspberry Pi - Hardware Flaws and Fixups?

It is not completely "extra" and "free". The current model B PCBs are also the model A PCBs. Redesigning for an updated model A would add (mostly one-time) costs. Also, note that it is not an "extra" option. You lose the option for "USB host" connectivity. So the "interface with the world" becomes the GPIO, CSI, DSI and USB-device.

Ah, that's no good, I thought you meant that there was an extra and unused USB client-mode port on the SoC.  I can't imagine many people being willing to give up their USB host-mode ability.

So, we're back to bit-banging for client-mode USB.  Far less than ideal, but among millions of Pi users, I bet that someone has a go at that one day.

another report of non-working TV after Pi usage:

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=7650

Bit bang a client-mode USB connection? Uhgh.

I'd look at using an MCP2200 or FTDI equiv connected to the UART on the GPIO pins with a couple of wires going to the un-connected d+/d- pins of the micro-usb connector.

And for the IO pin headers, how about using a header with pins long enough to plug in on both sides? The STM32F4 Discoverys I bought have nice long pins allowing IDC connectors top and bottom.

something different...  if there is ever a redesign,  perhaps splitting up the gpio header in a seperate UEXT and GPIO header.

Having a standard UEXT connector would mean that a lot of existing extension boards will be available.

So far i can see the pins are already there (serial,i2c,spi)

Or someone can make an adapter cable of course ...

And please add a RESET button !!

-J

Reviewing the rev 1.0 schematics and docs for the related parts, I found something that looks wrong.

The SMSC LAN9512 has two VDD18CORE pins that are internally connected between them and to the internal core 1.8V voltage regulator, those pins need to be connected externally as well and to a couple of filter caps.

The RasPi schematics shows those pins also connected to the +1V8 power line from RG1.

That looks wrong, the SMSC VDD18CORE pins should not be connected to +1V8.

-J

I fully agree! with your "VDD18CORE" remark.

Jamodio, have you found a "reset" pin on the 2835? The only thing I could find was "run". Would the CPU just pause when pulled low? I don't know.

While investigating this, I found that "D10" is not marked "(B)" as it should. (even though it is involved with the USB powersupply for the model A, the other side is not connected on the model A, so the component is redundant on model A).

Yes you are right D10 will not be needed for model A since as far as I know it does not include the SMSC LAN9512.

On the other hand even when the usb power control was with the poly fuses was implemented following the datasheet recommendations,

I'd have preferred a pair of USB switches instead. As we have seen from numerous reports the whole power strategy is questionable and

source of multiple problems.

About RESET I didn't check on the limited documentation if there is any reference about the the RUN pin works, I'd guess that probably

if we pull that pin down it may put the GPU in halt state but I'm not sure if it works as a complete reset.

-J

Jamodio,

   Very interesting observation about the VDD18CORE pins.

Can you tell what symptoms this might cause?