My nanonote is dead :(

Werner Almesberger werner at almesberger.net
Thu Apr 26 12:16:55 EDT 2012


lee jones wrote:
> battery charging is back now

The Ben can also start only on USB power. When debugging a "dead"
Ben, I'd therefore recommend removing the battery, which reduces
the number of states the system can be in.

The battery charging LED has a bit of a mind of its own and I
often find it more confusing than helpful. The CPU doens't
control that LED, so it does not indicate how anything beyond the
charger chip is doing.

I'd also remove any memory or I/O card because they can also
affect system behaviour.

Next, once the battery is out, disconnecting USB power for at
least 30 seconds reliably leads to a reset. Disconnecting for a
shorter period can cause a partial reset after which the Ben
appears to be dead.

The contacts on the bottom of the Ben's PCB can be surprisingly
difficult to use, so it's best to avoid them until more desperate
measures are needed.

Then you can check how things go with lsusb and dmesg. When the
Linux kernel on the PC finds an unresponsive device, it usually
complains quite verbosely about it. dmesg shows those complaints.

It can't hurt to give booting from USB a few tries, changing USB
cable, USB port, and if possible also PC. USB hardware problems
aren't extremely common, but they do happen. It's also better to
connect the Ben directly to a port on the PC and not through a
hub. (This removes several things that can go wrong, plus it
relaxes the protocol timing.)

The most common hardware failure of the Ben is a defect in the
cable connecting the main PCB with the display. The result is
usually a screen that never turns on. The rest of the device is
still operational and it should respond to USB. There is also a
small probability for only that cable's connector being loose,
which can produce effects similar to a damaged cable.

Since the Ben should still respond to USB, it usually doesn't
make sense to try to fix the cable before communication over
USB has been (re-)established.

It's not uncommon for a series of increasingly desperate
recovery attempts to damage more vital parts of the system
software, which can then result in the Ben to become completely
unresponsive on USB. The cure for this is an installation from
scratch using hardware-assisted USB boot.

The main steps for that are:

- disconnect all power. Leave the USB connector plugged in on
  the Ben and disconnect it on the PC side.

- wait 30 seconds

- short the contacts labeled "USB Boot", accessible via the
  battery compartment. Some people find the conductive rubber
  button that came with the Ben useful for this. If you don't
  have it, a pair of tweezers will do as well. You can also try
  a bit of wire.

  If you're familiar with soldering SMT components, you could
  solder a wire, 0R resistor, or just make a solder bridge. But
  better don't make this your first SMT soldering experiment :-)

- keeping the contacts shorted, plug in the USB cable on the PC

- you can release the contacts after plugging in USB

- check on the PC if the Ben has enumerated. It will show up as
  601a:4740

- then you can proceed with the USB boot process

If the Ben doesn't enumerate, chances are you didn't short the
USB Boot contacts. We've had cases where even people who knew
exactly how to do it still needed around ten tries before a good
enough contact was actually achieved. So some persistence may be
needed :-)

If none of this brings back at least USB, you could also take
the Ben apart and check the main PCB for foreign bodies, such as
scraps of metal that may have settled somewhere. A few blows of
"compressed air" may help to remove such items.

I hope this wasn't too confusing ;-) In any case, there are a
lot of Ben owners on the #qi-hardware IRC channel, so I'd
second Wolfgang's suggestion to get guidance for analyzing the
problem there.

- Werner




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