[time-nuts] 5370 processor boards available

John Seamons jks at jks.com
Wed Feb 26 21:06:00 EST 2014

On Feb 25, 2014, at 12:59 PM, John Seamons <jks at 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

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