> On Jan 31, 2017, at 7:19 AM, TJF <jeli.freih...@gmail.com> wrote: > > > > Am Montag, 30. Januar 2017 18:36:37 UTC+1 schrieb john3909: > Well, again it depends on what you mean by realtime. To most developers, it > means deterministic > > Yes, deterministic: > steady latency > the lowest possible steady latency > and since the AM335x ADC uses a sequencer to do the sampling, it is > deterministic, > > The sequencer garanties a deterministic process from analog line to the FiFo > buffer. You know that you cannot compute inside the FiFo. The data has to get > to a processor register first. And the complete process, from analog line up > to the processor register, has to be deterministic. > > and hence there is no difference between the PRU and ARM with DMA. > > There is a big difference, since the ARM gets loaded by other kernel tasks. > On Beaglebone hardware under LINUX, the PRU is the only system that can > garanty deterministic sampling (when bus access is unlimited). It is only the period between the samples that is important to be deterministic. After that, it doesn’t matter if there is any latency unless he is using the calculations in a control loop. If he is just doing phasor measurements, then latency isn’t important. You need to understand the application before you make assumptions like this.
Regards, John > > This shouldn’t be a pissing match as to how fast you can sample, but rather > focus on what the OP application was. In this case, since the PRU doesn’t > have the required math functions, > > The math in the original post contains simple table lookups, additions and > multiplications. It's easy to implement that on the PRU (, but not necessary > for 6 kSps). > > the PRU is only doing what the DMA is doing, moving samples from the FIFO to > DDR memory. Hence, why waste the PRU on such a trivial function. Rather save > it for something more useful. > > Yes, don't waste the PRUSS! That's why I didn't propose any customized > firmware, but libpruio. Even if Fabián doesn't need the digital features > (GPIO, PWM, CAP, QEP), he might use the trigger features to start the > measurement at the same phasing, in order to make results better comparable. > > Regards > > -- > 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/91f0dff0-4d11-460b-bec9-f3ffb785387f%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/91f0dff0-4d11-460b-bec9-f3ffb785387f%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 beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/E45CCE79-EEF1-48D7-A532-6045B5C58928%40gmail.com. For more options, visit https://groups.google.com/d/optout.
