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 >>> >>> 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 >>> >>> >> -- >> 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...@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 --- 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/ab17b85d-7f42-42cb-9793-ed7d04a44e27n%40googlegroups.com.
