That really does not make a lot of sense. I have five BBB's and a few Pocket Beagles, and they all free run within 50 ppm of where they are supposed to be at 24.000 MHz. 50 ppm error is about 3.5 seconds per day You can walk them in closer to 2 ppm(at least at room temperature), by changing C25 and C26 to 24 pF, rather than the factory supplied 18 pF. NTPD or timesyncd do not have any problem holding time on my Beagles within 20 milliseconds or so
I would look at the lid of Y2, the main 24 MHz crystal with a magnifying glass or microscope. The frequency is usually laser engraved in the metal lid. Where did you get your Beagle? --- Graham == On Wed, Jan 16, 2019 at 4:33 PM pbft <[email protected]> wrote: > Thanks. I'm not precisely sure of the terminology, but the BeagleBone > decides that the 'clocksource' is 24mHz. Its RTC will then gain *exactly* > two minutes every 24 minutes if you disable timesyncd. With pullup > resistors it will decide that the clocksource is 26mHz and the RTC will be > virtually perfect: > > debian@arm:~$ dmesg | grep -i timer > [ 0.000000] OMAP clockevent source: timer2 at 26000000 Hz > [ 0.000029] clocksource: timer1: mask: 0xffffffff max_cycles: > 0xffffffff, max_idle_ns: 73510017198 ns > [ 0.000039] OMAP clocksource: timer1 at 26000000 Hz > [ 0.000568] timer_probe: no matching timers found > [ 0.463409] clocksource: Switched to clocksource timer1 > > The custom cape leaves the 'boot pins' floating (unless I add the > pullups), and I get the same behavior with the BeagleBone running by itself > with no cape. > > On Wednesday, January 16, 2019 at 5:15:24 PM UTC-5, Graham wrote: >> >> The standard external clock frequency source for the BeagleBone Black is >> 24 MHz. >> >> Is that what you are referring to? >> >> Are you protecting all the "Boot Pins", so that your "Custom Cape" is not >> overriding the boot programming resistors on the BBB? >> >> --- Graham >> >> On Wednesday, January 16, 2019 at 3:25:48 PM UTC-6, pbft wrote: >>> >>> Quick update: I've built 4.18.20 from source, and it has the same >>> behavior. >>> >> -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/iZxmejC9750/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/040ea632-065a-4332-801a-794df698384b%40googlegroups.com > <https://groups.google.com/d/msgid/beagleboard/040ea632-065a-4332-801a-794df698384b%40googlegroups.com?utm_medium=email&utm_source=footer> > . > 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAC_N71q_1MqWrt9dUrpR52Hg6RhGvnbXaPV0hKoRybfmr_A04Q%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
