On Tue, 5 Jun 2018 at 02:11, <[email protected]> wrote: > I've come up with a software only workaround that can make sure a BBB will > always come up with a working Ethernet port - although it can take a few > minutes and require several automatic internal power cycles. > > You can read about it here... > > > https://wp.josh.com/2018/06/04/a-software-only-solution-to-the-vexing-beagle-bone-black-phy-issue/ >
While neat, I should caution that going into RTC-only mode on an unmodified BBB is rather hazardous. While most power rails shut down in this mode, SYS_5V does not. This is a situation similar to powering the BBB via the battery terminals, and will cause VDD_3V3B to fail to shut down (see [1] for details). This creates a situation where the 3.3V supply of hardware connected to the AM3358 (including various other chips on the BBB itself) remains on, yet the 3.3V I/O supply (VDD_3V3A) of the AM3358 itself is shut off. In this situation, if anything powered from VDD_3V3B drives a signal high (for example the serial buffer if a serial console cable is attached), this will result in serious violations of the Absolute Maximum Ratings (see [2]). My suggest would be to try using an external reset circuit that keeps nRESET low for a while during power-up (maybe combined with increased pull-up to make nRESET rise more cleanly when it is deasserted, despite the obnoxiously large cap). Matthijs [1] https://groups.google.com/d/msg/beagleboard/7sxPePT7wkM/3vFMPydR20IJ [2] https://groups.google.com/d/msg/beagleboard/7sxPePT7wkM/_oNSCta5WusJ -- 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/CAALWOA_NvQhBk3V8nNzn%2BHOkaHofZVYyWDzvn_Bh361UHAENgg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
