Hi y’all, Below is a snippet of an offline email exchange between myself and Gerald of Beagleboard.org <http://beagleboard.org/>… I’m reposting it here because I think it further clarifies some of the subtleties of what is being discussed here, specifically how brown-outs are what throw the wrench into a simple solution with existing hardware. It also illustrates some real-world constraints Gerald et al are facing around a potential solution at the board level. I hope this helps the bring anyone new to the discussion up to speed, as it helped me.
Best, ST > As I understand it, the crux of the problem -- what prevents the use of > existing off-the-shelf protection gear (like a stock UPS unit) — is the > necessity to physically close the reset switch to reliably reboot the board. > To be honest, I’m not even sure if this is even a real “Issue" (although it > is listed as such in the wiki), or just the upshot from a design decision you > consciously made (say, to reduce costs). I think there is broad agreement > that this is a problem. You’ve already built in some nice power management > hooks (interrupts, watchdog and such) that ought to allow the system to be > shut down gracefully when mains power is lost, it just can’t restart itself. > > Sort of. If you close the rest switch, you can trash the file system. What > you need is an interrupt to allow the processor to close the file system. > That exists today. Having the super cap or battery gives enough power for the > processor to complete that task and power down. When the DC is restored it > powers back up. The issue is if it is a brown out, that is where things get > messed up because it is not a clean shutdown and power up. > > Is the elimination of this particular physical switching requirement by > itself, a tough problem to solve? > No > > Would it take a lot of (cost-increasing) new hardware? > > Yes. At least $3. > > Would it need anything new in the kernel? > > No. > > Any software support? Wouldn’t it “Just work” as hardware outside of the OS? > > It can if it is done right. > > The more complete, robust “Reliability system," such as is being discussed in > the forum, is a whole different thing -- less issue, more feature > --effectively designed to replace the UPS with a custom backup power system > tailored for/integrated with the BBB, that also happens to mitigate the core > switching issue. You’re right, there there are a lot of opinions, and a lot > of different use cases here. > > Super Cap works fine. It is just the corner cases that need to be handled. > > If my reasoning is good, it would imply the overall “Reliability system" is a > good match for external solutions, whereas eliminating the physical switching > requirement would be a good thing to add to the mainline board. > > Yes as long as these additions are free or would actually reduce the cost. -- 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/20438005-A221-4DD1-A20F-EDF3998F152B%40gmail.com. For more options, visit https://groups.google.com/d/optout.
