They are actively being read on boot up and any loads on them, your other devices, will affect the booting mode of the processor.
Check the SRM https://github.com/CircuitCo/BeagleBone-Black/blob/master/BBB_SRM.pdf?raw=true , check the data sheet http://www.ti.com/product/AM3358 and search this mailing list. They will all tell you the same thing. You can also check: http://www.elinux.org/Beagleboard:BeagleBoneBlack#Expansion_Header_Pin_Usage Do not apply any load to those pins until after the SYS_RESET line goes high. Another thing you can try is to apply lower resistance pullups and pulldowns that match the ones on the board, except with a lower value. That will affect the video, but as you want to use them for outputs, the lower values should be OK. Gerald From: beagleboard@googlegroups.com [mailto:beagleboard@googlegroups.com] On Behalf Of claude.has...@gmail.com Sent: Wednesday, June 21, 2017 5:16 AM To: BeagleBoard <beagleboard@googlegroups.com> Subject: [beagleboard] using SYSBOOT pins as outputs....not booting from uSD Hey all Im using several of the SYSBOOT pins as outputs in my project. This means they are connected to the inputs of other ICs. My problem is that the Beaglebone no longer boots from uSD when connected to these peripherals.(sporadically, very rarely it does work) My assumption was that connecting SYSBOOT pins to INPUTS of other devices shouldnt affect booting, as they are not actively being driven! Is this wrong? I've also heard that the pullup/down resistors for the SYSBOOT pins on the Beaglebone are "weak" and additional resistors should be provided externally to make them more reliable. If so, which pins require which resistor value and which type(pull up or down)? It would be nice if the solution was a simply as providing some additional pullup/down resistors! can anyone shed some light on this? Regards Claude -- 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<mailto:beagleboard+unsubscr...@googlegroups.com>. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/91deec96-0428-4827-a77b-7595cf7e249b%40googlegroups.com<https://groups.google.com/d/msgid/beagleboard/91deec96-0428-4827-a77b-7595cf7e249b%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 beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/b9eb02d07c63422383880ccc54196957%40winhexbeus11.winus.mail. For more options, visit https://groups.google.com/d/optout.
