BeagleBone Black

[Tim Kientzle]

On Apr 28, 2013, at 10:03 AM, Tim Kientzle wrote:

> On Apr 28, 2013, at 2:37 AM, Iain Young wrote:
>> On 28/04/13 08:13, Tim Kientzle wrote:
>> 
>>> The 4-pin adapter I got from Adafruit for use with Raspberry Pi seems
>>> to work just fine, though the CircuitCo documentation has the instructions
>>> wrong.  It should be:
>>>   Black => Pin 1
>>>   Green => Pin 4
>>>   White => Pin 5
>> 
>> Hurm, I wonder what the other 3 pins are used for. They seem to be
>> undocumented in the SRM
> 
> I believe they're unconnected.  They're only there for compatibility
> with the common FTDI TTL-232R-3v3 USB-to-serial
> adapter that has a 6-pin connector.

Adafruit has added a photograph of using their 4-wire
adapter with the BB Black:

  http://www.adafruit.com/products/954

> 
>>> Harumph.  Looks like it always boots initially from the eMMC and
>>> U-Boot then looks at the boot switch to decide whether to continue
>>> from eMMC or uSD.
>> 
>> This would appear to be the default behaviour, but can be over-ridden
>> if I read the SRM correctly. For a one off force to uSD boot, hold down
>> the "boot" button". See Page 57 of the SRM
> 
> Tried that, but from watching the serial console, it's still
> loading U-Boot from the eMMC.  It's U-Boot that actually looks
> at that pin (there are some messages on the serial console
> about U-Boot inspecting a GPIO pin).

I was wrong.  The point that was confusing me:  The "boot switch"
is *only* read when you apply power.  Resetting the board
doesn't read the boot switch; you have to actually remove
power and then connect power while holding the switch.

U-Boot does fiddle GPIO pins, but only to set some LEDs to
indicate boot progress.


>>> This sucks:  the U-Boot on the eMMC doesn't have ELF support
>>> nor API support so can't load and boot ubldr.

Again, I was wrong.  It actually is possible to build a micro-SD image
and just boot it.

So far, I have managed to build an image that would boot
on either old or new BeagleBone.  The build isn't quite
repeatable --- I need to clean up some patches and fix a few
loose ends.

I was hoping to finish that tonight ...

Tim