You cannot just use a supercap. You have to use a boost switching regulator to keep the voltage on the processor constant while the supercap discharges. This is a lot more complicated than you suggest. You also have to deal with the case of brown outs where the power is only off for fractions of a seconds or cases where the power comes on and then off again before the board has fully powered up. This requires a power monitor and a state machine to only power the board on once the supercap is fully charged. Also, if you don’t recycle the power after a power fail, the BBB has the potential to lock and remains locked until the power is recycled.
Regards, John > On May 2, 2016, at 11:09 AM, William Hermans <yyrk...@gmail.com> wrote: > > Use a super capacitor. > > Ok, a little abstract . . . > > Use a super capacitor, and if using a console image . . . sudo apt-get > install acpid > > Then the board will automatically shutdown when 5V input goes missing. I'd > make sure you pick a super cap that can sustain the beaglebone for ~30 > seconds, even if not needed. Just in case. Typically though, here, we see > that the board shuts down within 5 seconds or so. Maybe slightly longer. > > On Mon, May 2, 2016 at 10:47 AM, William Hermans <yyrk...@gmail.com > <mailto:yyrk...@gmail.com>> wrote: > I have been building embedded systems for a while now and I am considering > using the beaglebone (BBB) for an upcoming project, but I am confused by > everything I read regarding the shutdown requirements. As an embedded system > the only way to turn it off is to simply shutdown the power with a switch, > yet my preliminary research indicates that this is a no-no as it may damage > the BBB and/or corrupt the file system. I also read a lot of comments > regarding voltage on the pins after a shutdown; in my case, very likely there > will be a CAT5 cable with live activity connected even after power down; > assume the magnetics should protect the BBB, but just checking. > > This is true of any system running an OS that is not red only. If you > unceremoniously yank the power, you're asking for trouble. > > I have used quite a few micro controllers and various self-standing systems, > but am fairly new to the BBB - still mostly reading about it. Am I missing > something? How can a device meant to be used in embedded systems not be > tolerant of power loss and be so finicky about power? > > It sounds like you're missing a lot. It sounds like you've had a lot of > experience with small micros, that run bare metal, but have have no, or > limited experience with using an embedded OS. > > Then if you stop and think of the cost of this board, and what the goal of > beagleboard.org <http://beagleboard.org/> was when the board was created. > Perhaps then it become clear as to how / why we're where we are in this > context. You can fix all of this yourself, using external hardware, and > custom software. > > By the way, I can see there is a battery backup circuit but I do not want to > use a lithium battery for safety/temperature/cost reasons. Using a large > capacitor also seems tricky as the shutdown may take a few seconds so I don't > see how that will work. > > Any suggestions would be greatly appreciated. > > Use a super capacitor. > > > > On Mon, May 2, 2016 at 8:39 AM, Gerald Coley <ger...@beagleboard.org > <mailto:ger...@beagleboard.org>> wrote: > > > On Mon, May 2, 2016 at 10:36 AM, Yiannis Papelis <ypape...@gmail.com > <mailto:ypape...@gmail.com>> wrote: > I have been building embedded systems for a while now and I am considering > using the beaglebone (BBB) for an upcoming project, but I am confused by > everything I read regarding the shutdown requirements. As an embedded system > the only way to turn it off is to simply shutdown the power with a switch, > yet my preliminary research indicates that this is a no-no as it may damage > the BBB and/or corrupt the file system. I also read a lot of comments > regarding voltage on the pins after a shutdown; in my case, very likely there > will be a CAT5 cable with live activity connected even after power down; > assume the magnetics should protect the BBB, but just checking. > > I have used quite a few micro controllers and various self-standing systems, > but am fairly new to the BBB - still mostly reading about it. Am I missing > something? How can a device meant to be used in embedded systems not be > tolerant of power loss and be so finicky about power? > > By the way, I can see there is a battery backup circuit but I do not want to > use a lithium battery for safety/temperature/cost reasons. Using a large > capacitor also seems tricky as the shutdown may take a few seconds so I don't > see how that will work. > > Any suggestions would be greatly appreciated. > > -- > For more options, visit http://beagleboard.org/discuss > <http://beagleboard.org/discuss> > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to beagleboard+unsubscr...@googlegroups.com > <mailto:beagleboard+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/4b2dc307-631d-405d-88d6-7537adb3ac29%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/4b2dc307-631d-405d-88d6-7537adb3ac29%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. > > > Main reason for the shutdown process is the corruption of the Linux file > system. > > If you have power on any signal when the processor is shutdown, then you are > asking for trouble. > > http://www.elinux.org/Beagleboard:BeagleBoneBlack#Expansion_Header_Pin_Usage > <http://www.elinux.org/Beagleboard:BeagleBoneBlack#Expansion_Header_Pin_Usage> > > > Gerald > > ger...@beagleboard.org <mailto:ger...@beagleboard.org> > http://beagleboard.org/ <http://beagleboard.org/> > gcol...@emprodesign.com <mailto:gcol...@emprodesign.com> > > > -- > For more options, visit http://beagleboard.org/discuss > <http://beagleboard.org/discuss> > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to beagleboard+unsubscr...@googlegroups.com > <mailto:beagleboard+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/CAHK_S%2BergZ8%2BPd5zBdxsHqJDzQphgPXKXF0oayzjV1PVHPY8kw%40mail.gmail.com > > <https://groups.google.com/d/msgid/beagleboard/CAHK_S%2BergZ8%2BPd5zBdxsHqJDzQphgPXKXF0oayzjV1PVHPY8kw%40mail.gmail.com?utm_medium=email&utm_source=footer>. > > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. > > > > -- > For more options, visit http://beagleboard.org/discuss > <http://beagleboard.org/discuss> > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to beagleboard+unsubscr...@googlegroups.com > <mailto:beagleboard+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/CALHSORqqALRuwazqWtdLK4uzTKe8EJShCx60943s3%3DuvWBrroQ%40mail.gmail.com > > <https://groups.google.com/d/msgid/beagleboard/CALHSORqqALRuwazqWtdLK4uzTKe8EJShCx60943s3%3DuvWBrroQ%40mail.gmail.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/E7D92EF1-EF2E-4761-A458-BE0CBB879901%40gmail.com. For more options, visit https://groups.google.com/d/optout.
