Expanding Chad's comment, in the Beaglebone Black System Reference Manual (Rev B, Jan 20, 2014)
https://github.com/CircuitCo/BeagleBone-Black/blob/390c46a03e039661aeca6eab22e6c383d8d537f8/BBB_SRM.pdf "Figure 39. Processor Boot Configuration" in "Section 6.8 Default Boot Options" says that the top two bits of the SYSBOOT register, SYSBOOT[15:14], seem to select which oscillator is used (19.2MHz, 24MHz, 25MHz, 26MHz). "Figure 38. Processor Boot Configuration Design" shows that SYS_BOOT14 and 15 are physically lcd_data14 and 15. "Table 12. Expansion Header P8 Pinout" shows that lcd_data14 and 15 are GPIO0[10] and GPIO0[11] in MODE0. Section "8.1.1 LCD Pins" contains the warning: "These pins are also the SYSBOOT pins. DO NOT drive them before the SYS_RESETN signal goes high. If you do, the board may not boot because you would be changing the boot order of the processor." In Fig 39, I see that SYSBOOT[15:14] == 01b results in 24 MHz, whereas 11b results in 26MHz, whose 8% difference may account for your ~5 sec offset per minute. (If 24MHz is the default, I'm not sure.) Best, Justin On Wednesday, January 4, 2017 at 5:12:24 AM UTC-8, cmbaker3 wrote: > > Johan, > That pin is used during the boot operation. > Check in the SRM for the default boot options. > > On 1/4/2017 5:39 AM, Johan Ribenfors wrote: > > We've recently found a strange problem. Repeatable across all eleven > boards we've tried so far. > > When pin 32 on P8 (gpoi0[11]) is pulled high via a resistor on boot, the > clock on the BBB runs ~7000 seconds slow a day. (~5 seconds a minute) > > If the pin is pulled low or left floating on boot, the clock keeps time. > > The device tree overlay was set to 0x37 for this pin - fast slew, output, > pullup, mode 7, but changing this has no effect. > > We were using Debian 7.9 with various programs installed, a few device > tree overlays applied and a custom cape when we noticed this, but it's > still the case using the Debian 8.6 image with no modifications, no dto and > no cape. > > We haven't been able to find anything online and don't really know where > to start looking. > > Any ideas? > -- > 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] <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/e0647cb0-ac27-44ed-a11b-a6f71b7ef077%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/e0647cb0-ac27-44ed-a11b-a6f71b7ef077%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > > > > -- > Chad Baker Memphis, TN > -- 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/79bac7d6-3011-44b5-95ac-61c43cb8525c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
