Colleagues,
I have an embedded application for a beaglebone blue in which it is a
NTP client and provides a precision pulse-per-second (PPS) TTL output to
an acoustic modem, all deep inside a pressure housing in an underwater
robotic vehicle
(https://www.whoi.edu/what-we-do/explore/underwater-vehicles/nereid-under-ice).
Our C code running on the beaglebone blue monitors the DC Jack
voltage, and executes a clean shutdown if DC Jack voltage is lost for a
period of time (system("sudo shutdown --poweroff 0 Shutting down due to
loss of DC power")).
Unfortunately for us, when power is restored to the DC Jack, the
beaglebone blue CPU does not power on automatically. The OSD3358 powers
up when the "POW" button is pressed, which pulls down the PMIC_IN_PB_IN
pin D20 on the OSD3358, but of course this button is inaccessible in our
application.
Does anyone have a tested hardware hack that will cause the
BeagleBone Blue to automatically reboot when power is restored to the DC
jack? I am thinking maybe a capacitor in series with a resistor between
DC jack and the based of an NPN transistor, whose emitter is grounded,
and collector momentarily pulls down PMIC_IN_PB_IN when DC power is
restored to the board. But there may be simpler solutions. Any
thoughts are welcome.
Thanks and Best Regards,
-Louis
--
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Louis L. Whitcomb, Ph.D.
Professor, Department of Mechanical Engineering
115 Hackerman Hall, 3400 N. Charles Street
Johns Hopkins University, Baltimore, MD, 21218-2681
l...@jhu.edu, 410-516-6724, https://dscl.lcsr.jhu.edu
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--
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