> > *Wrong again, UIO attempts to handle interrupts as events, but the concept > is slow (typically ms, not us)* >
You're full of it if you're trying to purport that any interrupt in Linux works in the uS range. On Thu, Mar 3, 2016 at 12:26 AM, John Syne <[email protected]> wrote: > Wrong again, UIO attempts to handle interrupts as events, but the concept > is slow (typically ms, not us) > > Regards, > John > > > > > On Mar 2, 2016, at 11:22 PM, William Hermans <[email protected]> wrote: > > *mmap isn't faster than a kernel driver (kernel code has priority over >> user space code) and you still cannot handle interrupts from user space. >> Anyway, you won’t find any drivers in the kernel implemented your way >> (/dev/mem, mmap). However, mmap is used in drivers to eliminate mem to mem >> copy when transferring data between user space and kernel space. * >> *Regards,* >> > *John* > > Now. not only are you wrong, but you're making stuff up. You can handle > interrupts from userspace, as much as iio can. But it's not my job to tell > you how. I will mention that perhaps you should look into "userspace > drivers". As far as whats faster ? who f***ing cares. mmap() is a lot > faster than the ADCs . . . and still not the point. > > The point is, if you need fast ADC you should be using the PRU, and then > you may want to seriously consider using an external module. That is, for > anything serious. It does not matter how much CPU mmap() or iio uses. As > any % can preempt other code that needs to run *now* thus creating > potential non determinism. > > > On Thu, Mar 3, 2016 at 12:12 AM, John Syne <[email protected]> wrote: > >> mmap isn't faster than a kernel driver (kernel code has priority over >> user space code) and you still cannot handle interrupts from user space. >> Anyway, you won’t find any drivers in the kernel implemented your way >> (/dev/mem, mmap). However, mmap is used in drivers to eliminate mem to mem >> copy when transferring data between user space and kernel space. >> >> Regards, >> John >> >> >> >> >> On Mar 2, 2016, at 11:04 PM, William Hermans <[email protected]> wrote: >> >> *From what I remember, the solution you proposed was using 90% of the >>> CPU. * >>> >> >> 93% CPU load when using one shot mode, and continuously opening / closing >> a file descriptor to the ADC module. There is no such load when using >> mmap(), as mmap() is light years faster. >> >> >> On Wed, Mar 2, 2016 at 11:52 PM, John Syne <[email protected]> wrote: >> >>> When the ADC is in continuous mode, you shouldn't read the data until it >>> has been updated. Simply reading the data over and over again to get the >>> same value that hasn’t been updated is just dumb. The interrupt tells you >>> when the conversion has been updated and then you read it. The point I was >>> making originally was that there was no need to use PRU to sample the ADC >>> at full speed. You can do the same from the IIO driver. Running at full >>> speed consumes less than 10% of the CPU. If the IIO driver was updated to >>> use DMA, then there would be no CPU utilization. From what I remember, the >>> solution you proposed was using 90% of the CPU. >>> >>> Regards, >>> John >>> >>> >>> >>> >>> On Mar 2, 2016, at 10:12 PM, William Hermans <[email protected]> wrote: >>> >>> *First, that isn’t going to work because the ADC uses a scan loop and >>>> unless you can respond to interrupts, you cannot determine when the ADC >>>> conversion has completed. There is a much simpler way to do this. Simply >>>> use the IIO driver and then* >>>> >>> >>> FIrst of all, it *will* work. I've done it, and it works. Second of all, >>> in continuous mode, values are put out as 32bit values. Only the first >>> 12bits is the actual ADC value. The next 4 bits is the channel ID( 0 - 7 ), >>> and the last 16bits reserved / unused. Thirdly, using interrupts in fast >>> moving code is about as bad of an idea as using try / catch blocks in fast >>> moving code. It adds code latency, and also introduces non deterministic >>> behavior. This is why iio does not work fast for short data sets. >>> >>> >>> *dd if=/dev/iio:device0 of=~/test* >>>> >>> >>> Maybe, but it's a terrible idea if the target is flash media. The ADC's >>> can, and will use up a lot of storage space, very quickly. Just using 7 >>> channel in one shot mode, one channel after the next. In a loop of 300k >>> iterations. I was using up ~3MB/s disk space. Maxed out, and all channel >>> used. The ADC's should use up ~9MB/s or more. >>> >>> >>> On Wed, Mar 2, 2016 at 4:06 PM, John Syne <[email protected]> wrote: >>> >>>> First, that isn’t going to work because the ADC uses a scan loop and >>>> unless you can respond to interrupts, you cannot determine when the ADC >>>> conversion has completed. There is a much simpler way to do this. Simply >>>> use the IIO driver and then read /dev/iio:device0 >>>> >>>> For example, do: >>>> >>>> dd if=/dev/iio:device0 of=~/test >>>> >>>> Enable the iio buffer and your file will receive samples at the >>>> configured speed. >>>> >>>> Regards, >>>> John >>>> >>>> >>>> >>>> >>>> On Mar 2, 2016, at 2:27 PM, William Hermans <[email protected]> wrote: >>>> >>>> errr oops, I sent too soon. mmap() is fast, and can actually read from >>>> the ADC faster than the ADC can update values. But, it's using the main >>>> processor to do so, and if you need to do more than just read the ADC. >>>> Additional processes would have to compete for processor time. So, if one >>>> does want / need to read at maximum speed, it might be wise to offload the >>>> main processor, by using a PRU. >>>> >>>> It would not matter if this were done in userspace, or kernel space. >>>> It'll definitely put a load strain on the ARM processor. >>>> >>>> On Wed, Mar 2, 2016 at 3:19 PM, William Hermans <[email protected]> >>>> wrote: >>>> >>>>> *You realize that you can read the ADC from Linux at full speed also? >>>>>> No need to use the PRU. * >>>>>> *Regards,* >>>>>> >>>>> *John* >>>>> >>>>> I do, because I've proven just that :) *mmap()* is dahmed fast . . . >>>>> >>>>> >>>>> On Wed, Mar 2, 2016 at 2:32 PM, John Syne <[email protected]> wrote: >>>>> >>>>>> You realize that you can read the ADC from Linux at full speed also? >>>>>> No need to use the PRU. >>>>>> >>>>>> Regards, >>>>>> John >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> On Mar 2, 2016, at 12:43 PM, TJF <[email protected]> wrote: >>>>>> >>>>>> Hello PatM001! >>>>>> >>>>>> There's libpruio <http://beagleboard.org/project/libpruio/>, which >>>>>> provides ADC sampling at full speed (200 kHz). You'll get rid of the >>>>>> exeptions (and the miss readings of the sysfs driver in case of sampling >>>>>> multiple channels). >>>>>> >>>>>> The downside: no C# binding yet. It's written in FreeBASIC/PASM and >>>>>> gets shipped with a C header. You may try SWIG <http://www.swig.org/> >>>>>> on the C header in order to generate a binding for your prefered >>>>>> language. >>>>>> >>>>>> If you try, please share your results, or at least report. >>>>>> >>>>>> BR >>>>>> >>>>>> -- >>>>>> 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. >>>>>> >>>>>> >>>>>> >>>>>> -- >>>>>> 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. >>>>>> >>>>> >>>>> >>>> >>>> -- >>>> 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. >>>> >>>> >>>> >>>> -- >>>> 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. >>>> >>> >>> >>> -- >>> 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. >>> >>> >>> >>> -- >>> 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. >>> >> >> >> -- >> 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. >> >> >> >> -- >> 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. >> > > > -- > 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. > > > -- > 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. > -- 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.
