On 12/11/2012 11:24 PM, Alan Stern wrote:
On Tue, 11 Dec 2012, Timur wrote:
I am talking about both devices loosing external power at the same time.
Losing external power is different from losing power.
I'm trying to be as precise as I can.
The N7 will then switch to it's internal battery.
Right. It will continue running, because the battery continues to
supply power. There is no interruption in the power flow.
Correct. Due to the internal battery, there is at no time an
interruption in the power flow of the host.
I guess anything could cause a loss of power. Turning off the car
ignition, for example.
What happens if the N7 doesn't lose its external power but the slave
does? If there's still a problem, that's a pretty good indication that
the N7 is working okay but the slave isn't.
I am using a regular OTG Y-cable. Both devices are using the same
external power source. When I disconnect and reconnect only the slave
(USB wise), there is no problem (see below).
Good hint. I found a reference to linux-tegra and will contact them.
Allow me to say that I got a little scared when you told me to "try
unplugging the slave" as a solution. Maybe you weren't all serious with
a list newbie?
I was perfectly serious. It's a legitimate debugging technique.
Unplug the USB cable, then plug it back in, then see what happens.
I got this wrong. It was your last sentence and I thought you were
suggesting this as a solution to the problem. I'm very sorry for
misreading you.
- Unplugging and re-plugging the slave device works well.
- Unplugging the Y-cable (disconnecting slave and external power at the
same time) then re-plugging the Y-cable works well.
- Disconnecting external power to both devices, then waiting for the
host screen to go off and waiting for up to 20 seconds longer (staying
in light sleep) does also work well. Please note: slave device was
completely off power for roughly 20 seconds and is not causing any issues.
The problem only occurs, when I pull external power, wait for the host
screen to go off, then wait another 60s or 10 minutes, this way making
sure the host will indeed transition into deep sleep. Plugging external
power then will wake both devices, but the host can no longer talk to
the slave.
Is this not strong evidence the problem is with the host?
Timur
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