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Setting the system to sleep/hibernate

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I'm using the camera for a specific event detection and processing. All other times, I actually do not require the system to be powered up and running. Is there a way/cmd to initiate and send the system into hibernation/sleep/low-power mode to save power? This is short of disconnecting the power totally from the camera and having to go through the boot sequence over again everytime the system starts up.


asked Dec 17, 2018 in User questions by adrielkuek (140 points)

1 Answer

0 votes

We have not tried this before but this seemed to work from the inventor console:

shell echo -n mem > /sys/power/state

The video stream stops and I am guessing the camera is suspended to RAM now.

But I have no idea how to wake it up... The device /dev/ttyACM0 still exists on my host but is unresponsive. So you would need to find a way, in linux generally speaking, to sleep for some time. Maybe setup some interrupt of sorts. But beware that we did not implement a 32kHz crystal on jevois for the real time clock (RTC) so any waking up based on RTC operation will likely not work.

You could instead reduce the CPU frequency using

setpar cpumax 120

which will set it to 120MHz and should consume minimal power if you also just stop capturing video in your code and just idle away. Finally note that the fan is always on. You would need to add a switch to its positive wire to turn it off, or maybe go fanless if you can operate at reduced frequency even when awake so you won't overheat (e.g., 600MHz should be ok with no fan under full CPU load).

answered Jan 4 by JeVois (34,860 points)