From: <[email protected]> Reply-To: <[email protected]> Date: Saturday, March 22, 2014 at 10:08 AM To: <[email protected]> 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 isn¹t 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 haven¹t 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 [email protected]. > 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
