ooops, I forgot the main concern. The MSP430 could also be use as an external smart watchdog. Just by poking a GPIO pin once in a while from a beagelbone. In code this would be very easy, and not processor intensive at all.
- BBB twiddles GPIO pin - Pin interrupt fires on MSP430, and toggles a bit flag. - timer period ends, and sees bit toggled, or not. - if toggled, repeat cycle. - if not toggled disconnect / reconnect power to the Beaglebone, and then toggle the reset switch. Another nicety of the G2553 MCU is that it has an on die temp sensor. Then since the MCU will spend 90% + of it's time in sleep mode, core temperature will not be above ambient temperature by very much, if at all. So you get a temperature sensor for free, if you care to hook up UART, SPI, or I2C back to the beaglebone. I think that honestly, the MSP430G2553 is even too much hardware for the particular use case. But it's the only MCU I know of that uses so little power, costs so little, nd has all the required features for an external smart watchdog that can "physically" interact with an SBC, as well as monitor power on it's own. On Sun, May 15, 2016 at 7:46 PM, William Hermans <yyrk...@gmail.com> wrote: > *What the BBB needs is not so much a watchdog timer, but an intelligent* >> * power monitor. If that processor (and it could be very simple) does* >> * *not* have an operating system but simply runs embedded firmware, then* >> * it will not suffer from shutdown problems as does the BBB.* >> >> * It could have an operating system, but should not depend on file* >> * systems being set up properly (a la windows or linux, I think).* >> >> * You could use something as simple as an Arduino.* >> >> * Harvey* >> > > I would probably never use an Arduino for this purpose. The cost is too > high for starters. > > An MSP430G2553 is perfect for this usage because it is an extremely low > power MCU, that has hardware SPI, UART, I2C, WDT, ADC, PWM . . . and at > least 14-16s pin available for use after the bare minimum are used for > power, gnd, reset, etc. This MCU is also well supported in CCS, as well as > through gcc, and the MCP430 MCUs are well known, and proven. > > So, the G2553 has it's own WDT in case it ever get's stuck. It has it's > own hardware ADC so it can monitor input power it's self. Then it has > GPIO's which can be used to power down a BBB though toggling the power > button, or reset the board by disconnecting power from input as needed. > Plus it has it's own POR, and BOR features built in. As well as being an > MCU with internal flash for storage it is for all intents and purposes > immune to power loss. > > Trust me though. My buddy and I have discussed this a lot over the coarse > of the last 3 or so years, and even more lately as we've realized that > reset on the BBB is essentially broken since it's only a soft reset. That > requires the input power to be completely disconnected for a short amount > of time. > > Anyway, if I knew PIC, or NXP MCU's as well as the value line MSP430's, I > might consider one of those too. But seriously, beating the power usage of > a valueline MSP430 would be really hard. They can operate on a single > button cell for over 10 years. > > > On Sun, May 15, 2016 at 6:00 PM, Harvey White <ma...@dragonworks.info> > wrote: > >> On Sun, 15 May 2016 17:08:40 -0700 (PDT), you wrote: >> >> > >> >Sorry guys. I might be confusing my terms here, or misusing the phrase >> >'watchdog timer'. Would 'hardware watchdog circuit' fit? "Intelligent >> >power switch?" I'm not quite sure what to search for! >> >> I generally call a watchdog timer (and it can be external if desired) >> as a timer that must be continually refreshed, if it times out, it >> resets the microprocessor. However, the processor remembers that it >> has been reset by a watchdog (most of them ought to), and then your >> bootup routine will know that the program hung somewhere and didn't >> reset the watchdog timer in time. >> >> What the BBB needs is not so much a watchdog timer, but an intelligent >> power monitor. If that processor (and it could be very simple) does >> *not* have an operating system but simply runs embedded firmware, then >> it will not suffer from shutdown problems as does the BBB. >> >> It could have an operating system, but should not depend on file >> systems being set up properly (a la windows or linux, I think). >> >> You could use something as simple as an Arduino. >> >> Harvey >> >> > >> >The circuit I'm looking for is what John3909 is describing; something to >> >address the corner-cases around power and ensure graceful, and hands-off, >> >system recovery amidst all of the corner cases (brownouts, drop+restart >> >(incl at 'inconvenient' times, ie during shutdown, etc)). >> > >> >Fwiw, my application is already kicking the onboard watchdog, and relying >> >on its reboot if the software system fails. I need to make sure that >> that >> >reboot ALWAYS happens, no matter what the power throws at it, as the >> system >> >will be installed in walls, ceilings and such. >> > >> >Does anyone know of a good public-domain/open-source external circuit >> >design that might work around the BBB (or something close -- a good >> >starting point)? Or, even better, would anyone be able & willing to >> share >> >their circuit design? I realize that this kind of circuit requires some >> >solid engineering to get right. The EE part is a stretch for me, >> >capability-wise, but I can offer software services in trade for hardware >> >help. >> > >> >I'm personally blocked by this issue, and just trying to work out the >> best >> >path forward, but I'd love to see this problem definitively solved for >> >everyone using the BBB. It is such a great platform. I'd love to ensure >> >it'll always be online and ready for what we all throw at it. >> > >> >Best, >> >ST >> >> -- >> 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/pg6ijb17s4ie0fs5rv13vi67hdcd1fsf10%404ax.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. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CALHSORqJbZDscGDFQNs1dG5UUHE3Z%3DzHPX5AFk1hFpRHVpSZ0A%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
