That would be nice as well. But that is your call. Gerald
On Sun, Sep 6, 2015 at 8:46 PM, rattus <[email protected]> wrote: > You may have seen I mentioned that no signals would be driven onto the BBB > expansion headers until enabled to do so (if I forgot to mention that, they > won't be); all other pins are inputs to the expansion card and thanks to > Graham's advice will be powered first to ensure protection diodes will not > interfere with the boot configuration. > > Mike > > On Saturday, September 5, 2015 at 7:10:43 PM UTC-6, Gerald wrote: >> >> Well, I think there is a better way that relying on luck. I suggest you >> take a look at >> http://www.elinux.org/Beagleboard:BeagleBoneBlack#Expansion_Header_Pin_Usage >> >> Gerald >> >> On Sat, Sep 5, 2015 at 7:51 PM, rattus <[email protected]> wrote: >> >>> I went with a little LDO to provide a local 3.3V source; looks like >>> it'll pop up in about 50-100uS after 5V is available. >>> >>> Thanks again. >>> >>> >>> On Saturday, September 5, 2015 at 12:22:21 PM UTC-6, Graham wrote: >>>> >>>> I think the VDD_3V3B rail is deliberately held off until the unit has >>>> started booting, >>>> and has already read the boot instructions. It is not a rise time >>>> issue. >>>> I suspect it was done deliberately to help with the "don't drive the >>>> rest of the pins" issue. >>>> >>>> A little 5V to 3.3V regulator to power your LVC "input" IC will work >>>> nicely. >>>> Provided that it is powered at the same time the BBB is. >>>> That is, use VDD_5V if powered from the power jack. >>>> >>>> Relative to power appearing at the power jack: >>>> SYS_5V is delayed 50 ms. >>>> VDD_3V3B is delayed 100 ms. >>>> SYS_RESETn is delayed ~130 ms. >>>> >>>> I have not measured power supply sequencing when powered by USB. >>>> >>>> Or if you are dealing with both I and O on the boot pins, use something >>>> like >>>> a 74CBTLV3126 bus switch / transmission gate to isolate your circuitry >>>> from the BBB while it is booting. Just make sure the bus-switch / >>>> transmission-gate >>>> is powered while the BBB is booting. >>>> >>>> This issue only comes up about once a week here on the forum. :-) >>>> >>>> --- Graham >>>> >>>> >>>> -- >>> 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. >>> >> >> >> >> -- >> Gerald >> >> [email protected] >> http://beagleboard.org/ >> > -- > 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. > -- Gerald [email protected] http://beagleboard.org/ -- 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.
