The documentation and datasheets on this seem contradictory at best. You are correct in quoting http://www.ti.com/lit/ug/slvu551h/slvu551h.pdf in that it states, "TPS65217C is also targeted at the AM335x processor in the ZCZ package, but the DCDC1 output voltage is set to 1.5 V to supply DDR3 memory. This version does not support AM335x RTC-only operation." However reading the data sheet for the TPS65217C found here, http://www.ti.com/lit/ds/symlink/tps65217c.pdf , one finds on page 15 the difference between the sleep and the off modes of operation wherein the setting of the OFF bit in the STATUS register determines the state that is entered and what rails remain up. if one enters sleep, the RTC rail looks like it stays up with all other rails down (escentially hibernation) with darn near zero power usage. I'm hoping to find the relivant source in the next couple days (sources for pm-hibernate, pm-sleep, shutdown, halt, etc. and the kernel sources) that invoke these states. It looks like just maybe a bit of an appropriate software hack (never going to off state, but only to sleep) could eliminate the need for off board / off chip RTC.
Eric On Fri, May 30, 2014 at 7:30 AM, Mike <[email protected]> wrote: > Changed subject as this is getting away from Joshua's original post > about the CryptoCape. > > On 05/29/2014 10:01 PM, Eric Fort wrote: > > Are you guys talking about the crypto cape or the RTC cape? The crypto > capediscussed in this thread uses a ds3231 not a ds1307. Also why anyone > *needs* the rtc cape I don't get. just keep the rtc rail powered on the > processor. That I believe is a software issue. > > Eric > > > From TI User guide on the TPS65217 [1] I find this. > > TPS65217C is also targeted at the AM335x processor in the ZCZ package, > but the DCDC1 output voltage is set to 1.5 V to supply DDR3 memory. *This > version does not support AM335x RTC-only operation.* > > Gerald has stated before that there *isn't* a battery backed RTC > available. Why would I even question this, faulty memory on my part > perhaps? > > The question that still nags me is how does one set a sane time value from > a battery backed RTC as early as possible during bootup. Systemd only > supports setting the time from rtc0, no options to specify any other > device. Sillyness IMNSVHO... > > I probably have already answered my own question, just use a shell script > ala init.d and be done with it. > > Mike > > 1. http://www.ti.com/lit/ug/slvu551h/slvu551h.pdf > > -- > 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.
