http://electronics.stackexchange.com/questions/221292/tip-barrel-test-of-oscilloscope
Regards, John > On Jul 6, 2016, at 7:13 PM, Joshua Collins <[email protected]> wrote: > > Hi Robert, > > I thought I had checked for power supply issues and not found anything, but I > checked again and found problems. Our cape board powers the beaglebone > through the VDD_5V pins on the header. > > Here are the VDD_5V (blue) and VDD_3V3B (yellow) rails when the beaglebone is > powered from our custom cape, captured at a point during flashing: > > > > <https://lh3.googleusercontent.com/-EBhCzNStAqA/V322CKFxxjI/AAAAAAAAAKo/iLdc--L8XlAkpezfA97WvPimrM6djzLvACLcB/s1600/VDD_5VandVCC_3V3BSpike3.png> > > <https://lh3.googleusercontent.com/--5ZnqjQBwPE/V322FNIMPFI/AAAAAAAAAKs/i-t4gxU0UuYtlRq427FYuJP1XSEo9KevwCLcB/s1600/VDD_5VandVCC_3V3BSpike4.png> > So, we've found a problem. > > But here is what those same rails look like when the beaglebone is powered by > a 5A lab supply through the barrel jack, without our custom cape connected - > it's interesting that there are still significant (albeit much smaller) > fluctuations. Are they large enough to be a problem? I wonder whether the > beaglebone has enough local capacitance to handle the eMMC's power demands. > > > <https://lh3.googleusercontent.com/-qKEWPJOYYQs/V322TTKacRI/AAAAAAAAAKw/LQpcLiOtvU0C3AXJAP7OmFBO9Y8YFlxaQCLcB/s1600/BenchSupplyVDD_5VandVCC_3V3BSpike3.png> > > <https://lh3.googleusercontent.com/-Mkjpi_c7DAk/V322W7WQYbI/AAAAAAAAAK0/XyDGRYQoaIYYle0mWiYRWc8EDBdY9gSawCLcB/s1600/BenchSupplyVDD_5VandVCC_3V3BSpike4.png> > > <https://lh3.googleusercontent.com/-mV_zjIGnWmg/V322aAzd15I/AAAAAAAAAK4/-eHHLUlfY7whIkh7xglC_fbW7wfqkx_4gCLcB/s1600/BenchSupplyVDD_5VandVCC_3V3BSpike5.png> > > > <https://lh3.googleusercontent.com/-2Va53Bhhbkw/V322dKWg9RI/AAAAAAAAAK8/cmt0Ki7HN54eUsuthwxgGlPqQvP0iVGvgCLcB/s1600/BenchSupplyVDD_5VandVCC_3V3BSpike6.png> > > Thank you for your help, > Joshua Collins > > -- > For more options, visit http://beagleboard.org/discuss > <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] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/815d709d-9b51-495b-a8b9-c29b213bd0b7%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/815d709d-9b51-495b-a8b9-c29b213bd0b7%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <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/830F27D9-5C65-481E-9DA8-C41B3AC34452%40gmail.com. For more options, visit https://groups.google.com/d/optout.
