That fix presumes that the power line never quits at
inappropriate times. This winter has provided me with
ample reminders that power can go out anytime.
I think a better solution would be to find a very large
"super cap" and power the BBB from that while giving it
a power fail interrupt to quickly sync the file system.
-Chuck Harris
John Seamons wrote:
On Feb 25, 2014, at 12:59 PM, John Seamons <j...@jks.com> wrote:
I may have a solution for the power-off problem that doesn't involve batteries
or supercaps. It has the added advantage of providing instant-on.
From the latest documentation:
"One solution to the annoyance of having to halt the BBB before the instrument
is
powered off is simply to keep the BBB running by providing it a secondary source
of power via the USB-mini port. The BBB already understands how to select
between
two sources of power: the USB-mini and +5V barrel connectors (the latter of
which
is actually being delivered from the 5370 via the board expansion connectors).
The
app detects when the instrument has powered down and resumes running when power
is
restored. USB power could come from an external USB hub or charger. You may have
to obtain a longer USB cable than the one supplied. Be certain to only use the
USB-mini connector that is adjacent to the Ethernet RJ45 connector. Do not use
the
USB-A connector on the other end of the board as that port will not accept input
power.
Some of you might even figure out how to derive +5V for the USB-mini cable from
the 5370 oven power supply card that is always powered if the instrument is off
but the line cord is plugged in. But beware of the potential problem of
conducting
noise from the BBB to the reference oscillator over such a connection. Some
experimentation and measurement is necessary. The planned USB/Ethernet connector
card that replaces the current HPIB one at the back-panel could host a voltage
regulator. Aligator clip connections to the '+25V UNREG' and GND test points on
the oven power supply would alleviate the need for any soldering."
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