I am still not sure why anyone would need / want all this complexity. Living offgrid, powered by solar panels which charge a battery bank, which then powers our home via an Inverter . . . I am not sure why the same concept can not be used on the BBB.
1) Power the BBB via a small rechargeable ~5V power source. 2) charge this ~5V power source via AC mains, solar power, whatever. 3) Monitor power on the charge input, and when absent send a message to the kernel to shutdown / hybernate. Then, all you need is to make sure your power source can work a few minutes with no input power applied. Perhaps even double this value for "safety". The way I see things, there is nothing to complex about all this at all. On Mon, Mar 24, 2014 at 10:41 AM, John Syn <john3...@gmail.com> wrote: > > From: <kb2...@gmail.com> > Reply-To: <beagleboard@googlegroups.com> > Date: Saturday, March 22, 2014 at 10:08 AM > To: <beagleboard@googlegroups.com> > Subject: [beagleboard] Hardware watchdog for BBB > > HI, I have been working for a wile on safe power supply for BBB with > backup power provided by supercapacitors. In case of power failure there > is just enough time to safely and nicely shut down BBB. For some reason > BBB does not always wake up fully. I need hardware dogwatch. Did anybody > design such a thing? I was able to find some design for ardunio: > http://www.playwitharduino.com/?p=291. > Anybody has any experience with hardware dogwatch for BBB?? > Thanks in advance > Robert > > Hi Robert, > > Developing a power supply that ensures a reliable shutdown down in the > event of a power failure isn't a simple design. You really need to monitor > the input power supply and the state of the kernel to determine when to > remove and reapply power to the BBB. You have to consider the corner cases > such as: > > 1. power failure could occur during the boot up sequence > 2. power failure occurred, triggering a shutdown sequence and then > power is restored during the shutdown sequence. > > With Linux, you cannot arbitrarily remove power during the boot up > sequence and you cannot simply reapply power during the power down > sequence. In the first case, when would it be safe to simply remove power > to the BBB and in the second case, when would it be safe to recycle the > power to the BBB. Currently there is no external info to determine the > state of the kernel so you would have to add a kernel driver which will > control a GPIO to signal when the kernel is in a safe mode (all volatile > info written to non-volatile memory) and also monitor a GPIO used to > interrupt the kernel when a power failure occurs. > > So now, you need an external state machine which tracks the input power > supply, state-of-kernel and charge state of super caps. Timers are also > required to ensure a proper power recycle. > > I hope I have covered everything you need to consider in your design, but > perhaps others has some insights I haven't considered. > > Regards, > John > > -- > 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. > For more options, visit 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. > For more options, visit 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. For more options, visit https://groups.google.com/d/optout.
