Alright then. Something in the chip is indeed flipping them on the same clock edge.
> On Aug 10, 2020, at 11:58 AM, Mark A. Yoder <mark.a.yo...@gmail.com> wrote: > > > <ToggleTwo.jpg> > On my 100MHz 'scope they look the same. I think it's one instruction > toggling the pair. They are toggling at some 268KHz. > > --Mark > On Monday, August 10, 2020 at 11:43:49 AM UTC-4 stl...@gmail.com wrote: > It’s unlikely to be exactly the same time, it’s just within some undefined > margin for error. Compiled C code can get the two pins set within a small > number of 1 GHz clocks. With a fast enough scope, you’’ll probably find at > least a few ns difference, if this isn’t obscured by parasitic capacitance in > the traces and wiring. Sure, this is a 3 orders of magnitude less than > gpiod, but there are folks out there working in femtoseconds for whom a > nanosecond would be far too long. Time is a very stretchy thing. > > >> On Aug 10, 2020, at 11:33 AM, Mark A. Yoder <mark.a...@gmail.com >> <applewebdata://C3504F9C-0AC0-4B59-9AE1-C2D494C477A5>> wrote: >> > >> Interesting.... I wrote a c version >> <https://github.com/MarkAYoder/BeagleBoard-exercises/blob/master/gpiod/bulk.c> >> and the pins are toggle at the exact same time. Now, how to get gpioset to >> work correctly. >> >> --Mark >> >> On Monday, August 10, 2020 at 10:27:08 AM UTC-4 Mark A. Yoder wrote: >> Yes, but the hardware on the am335x can toggle multiple pins on the same >> chip in the same clock cycle. Seems like the software should be able to >> support it. >> >> On Monday, August 10, 2020 at 10:20:10 AM UTC-4 evilw...@gmail.com <> wrote: >> software takes time to execute. >> >> >> On 8/10/2020 7:09 AM, Mark A. Yoder wrote: >>> I'm starting to play with gpiod on a Beaglebone Black. One of the >>> advantages of gpiod is you can toggle multiple pins on the same chip all at >>> once. >>> So I try: >>> while true; do >>> gpioset 1 18=0 19=0 >>> gpioset 1 18=1 19=1 >>> done >>> >>> This is toggling pins P9_14 and P9_16. I expect to see the two pins toggle >>> on at the same time, but what I get is >>> a 4 microsecond delay from P9_14 switching and P9_16 switching. >>> >>> Should there be such a long delay? I'd expect the two to switch at the >>> same time (which is what happens when toggle pins via the PRU). >>> >>> I do the same experiment with python and I see a 70 us delay. >>> >>> --Mark >>> On Friday, March 27, 2020 at 3:58:21 PM UTC-4 Drew Fustini wrote: >>> On Fri, Mar 27, 2020 at 8:45 PM John Allwine <jo...@allwinedesigns.com <>> >>> wrote: >>> > >>> > I don't intend to toggle a GPIO as fast as possible (except to test), but >>> > from a performance standpoint that demonstration seemed to indicate that >>> > there are issues with sysfs. Hopefully, libgpiod will prove to be better! >>> >>> Bartosz explains the differences and improvements that new gpiod >>> interface provides in this talk: >>> https://www.youtube.com/watch?v=cdTLewJCL1Y >>> <https://www.youtube.com/watch?v=cdTLewJCL1Y> >>> >>> Essentially, if you need read or set multiple lines, it is faster. >>> Also, it has an improved way to read events as well. >>> >>> Slides if you prefer over video: >>> https://ostconf.com/system/attachments/files/000/001/532/original/Linux_Piter_2018_-_New_GPIO_interface_for_linux_userspace.pdf?1541021776 >>> >>> <https://ostconf.com/system/attachments/files/000/001/532/original/Linux_Piter_2018_-_New_GPIO_interface_for_linux_userspace.pdf?1541021776> >>> >> >>> -- >>> 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 beagleboard...@googlegroups.com <>. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/beagleboard/16a18eef-a649-46d9-b126-f774a8eb1522n%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/beagleboard/16a18eef-a649-46d9-b126-f774a8eb1522n%40googlegroups.com?utm_medium=email&utm_source=footer>. >> >> >> -- >> 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 beagleboard...@googlegroups.com >> <applewebdata://C3504F9C-0AC0-4B59-9AE1-C2D494C477A5>. > >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/beagleboard/ab17b85d-7f42-42cb-9793-ed7d04a44e27n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/beagleboard/ab17b85d-7f42-42cb-9793-ed7d04a44e27n%40googlegroups.com?utm_medium=email&utm_source=footer>. > > > -- > 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 beagleboard+unsubscr...@googlegroups.com > <mailto:beagleboard+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/7b503014-a032-46cd-8733-a5ade72c1055n%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/7b503014-a032-46cd-8733-a5ade72c1055n%40googlegroups.com?utm_medium=email&utm_source=footer>. > <ToggleTwo.jpg> -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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