No in my case 50 - 60 samples are not sufficient in my case.why? let me explain my objective in a brief:
" I want to sample power supplied, So my basic waveform is of 50 /60 Hz but supply is coming from inverter( DC to AC converter) and as its coming from converter it will have high frequency harmonics / noise; bcoz inverter switching freq can be from 4 KHz to 6 KHz ". Hence as per Nyquist criteria, to reconstruct or analyze, I require samples at higher freq than the that. Hope it clears the things :-) Once again my sincerest gratitude for guidance. On Wednesday, September 30, 2015 at 12:22:13 PM UTC+5:30, William Hermans wrote: > > *But if that is the case, than data would come randomly to me!! 2nd >> channel 1st and than maybe 4th channel, dont you think its risky? specially >> in my case, I want to analyze the data, filter it if required & reconstruct >> the waveform!! :-) your explanation is scaring me :-p* > > > No not really, as we're talking about micro or nano seconds. Also, one of > the serious electronics engineers around who knows exactly how the hardware > works might be able to tell you exactly how the ADC works. I can not. > Passed that, do you really really need more than a few adc readings a > second to do what you need ? By a few, I mean anywhere from 10 to 50 a > second. Now if you're calculating / changing engine timing on a very high > RPM engine or something . . .maybe I could understand but yeah heh. > > On Tue, Sep 29, 2015 at 11:38 PM, Rathin Dholakia <[email protected] > <javascript:>> wrote: > >> >> >>> >> Non blocking, reads, sees nothing, and then continues execution. So for >>> example if you have two reads back to back on two different channels, it >>> would not matter in what order the data was ready. The first channel to >>> have data would very likely "display" that data first. But in blocking >>> mode. EVERY read after the current read has to wait until it is successful. >>> >>> >> But if that is the case, than data would come randomly to me!! 2nd >> channel 1st and than maybe 4th channel, dont you think its risky? specially >> in my case, I want to analyze the data, filter it if required & reconstruct >> the waveform!! :-) your explanation is scaring me :-p >> >> >> >>> This is why blocking uses less CPU, while non blocking uses more. 10-11% >>> could possibly still be non blocking though, and it not so much as a rule, >>> as much as possible indicator. 20% CPU, i'd probably bet on it. ~10% . . >>> .is hit and miss. I can tell you that using blocking reads with socketcan ( >>> CANBUS peripheral ), uses like 0-2% CPU . . . >>> >>> On Tue, Sep 29, 2015 at 11:06 PM, William Hermans <[email protected]> >>> wrote: >>> >>>> I pretty much followed this guide for ADC setup >>>> http://processors.wiki.ti.com/index.php/Linux_Core_ADC_User's_Guide#Usage >>>> >>>> On Tue, Sep 29, 2015 at 11:03 PM, William Hermans <[email protected]> >>>> wrote: >>>> >>>>> Well it might be you're running in continuous mode. That much I do not >>>>> know, but it could be difference in kernels ? I could not say. >>>>> >>>>> On Tue, Sep 29, 2015 at 11:00 PM, Rathin Dholakia < >>>>> [email protected]> wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> I tried running your code and I was successful and unsuccessful >>>>>> both!! :-) >>>>>> >>>>>> Success: I could compile code it compiled and when I put "time >>>>>> ./test" I gave me following output >>>>>> >>>>>> real 0m0.011s >>>>>> user 0m0.000s >>>>>> sys 0m0.008s >>>>>> >>>>>> unsuccessful: it didn't show any readings!! >>>>>> My guess is it has something to do with my kernel preemtion, isn't it? >>>>>> >>>>>> On Wednesday, September 30, 2015 at 11:18:20 AM UTC+5:30, William >>>>>> Hermans wrote: >>>>>>> >>>>>>> Oh, and that is using one shot mode. I did not think to use >>>>>>> continuous. BUt I really wanted to see how slow using open(), read(), >>>>>>> and >>>>>>> close() really were. Because I had done a lot of reading on the >>>>>>> subject, >>>>>>> but never actually used it( I always used mmap() ). >>>>>>> >>>>>>> On Tue, Sep 29, 2015 at 10:41 PM, William Hermans <[email protected]> >>>>>>> wrote: >>>>>>> >>>>>>>> So, I got bored, and decided to do some "screwing around". But took >>>>>>>> me a while because I had not used, or setup the ADC peripheral before, >>>>>>>> but >>>>>>>> . . . here is some quick and dirty code, using std API stuff - Which >>>>>>>> breaks >>>>>>>> all the rules I spoke of in my second post heh. But still pretty >>>>>>>> darned >>>>>>>> fast. I'd be happier if I could use mmap() directly on >>>>>>>> /sys/bus/iio/devices/iio:device0/in_voltage0_raw, but either I've been >>>>>>>> trying to use an improper mode of operation. Or mmap() on that file >>>>>>>> location is not supported. So, might be forced to use mmap() on >>>>>>>> /dev/mem . >>>>>>>> ..ug! >>>>>>>> >>>>>>>> #include <unistd.h> >>>>>>>>> #include <sys/stat.h> >>>>>>>>> #include <fcntl.h> >>>>>>>>> #include <stdio.h> >>>>>>>>> #include <errno.h> >>>>>>>>> #include <stdlib.h> >>>>>>>>> >>>>>>>>> void read_adc(int fd) >>>>>>>>> { >>>>>>>>> char adc[5] = {0}; >>>>>>>>> int len = read(fd, adc, sizeof(adc - 1)); >>>>>>>>> adc[len] ='\0'; >>>>>>>>> printf("%s ", adc); >>>>>>>>> } >>>>>>>>> >>>>>>>>> int main() >>>>>>>>> { >>>>>>>>> const char *fname = >>>>>>>>> "/sys/bus/iio/devices/iio:device0/in_voltage0_raw"; >>>>>>>>> int count = 0; >>>>>>>>> >>>>>>>>> while( count++ <= 1000){ >>>>>>>>> int fd = open(fname, O_CREAT | O_RDONLY); >>>>>>>>> if(fd == -1){ >>>>>>>>> printf("error: %s\n", strerror(errno)); >>>>>>>>> exit(1); >>>>>>>>> } >>>>>>>>> >>>>>>>>> if(count % 15 == 0 && count != 0) >>>>>>>>> printf("\n"); >>>>>>>>> >>>>>>>>> read_adc(fd); >>>>>>>>> >>>>>>>>> close(fd); >>>>>>>>> } >>>>>>>>> printf("\n"); >>>>>>>>> >>>>>>>>> return 0; >>>>>>>>> } >>>>>>>>> >>>>>>>> >>>>>>>> Output: >>>>>>>> debian@beaglebone:~$ time ./test >>>>>>>> 4016 4020 4007 4010 4008 4010 4005 4005 4013 4015 4015 4011 4008 >>>>>>>> 4001 >>>>>>>> 4010 4006 4006 4011 4007 4011 4003 4009 4006 4005 3995 3999 4005 >>>>>>>> 4000 3997 >>>>>>>> 4008 4016 4009 3997 4008 4011 4013 4011 4012 4009 4006 3997 4007 >>>>>>>> 4007 3999 >>>>>>>> 4014 4014 4007 4015 4008 4011 4012 4012 4007 4013 4016 4017 4016 >>>>>>>> 4016 4013 >>>>>>>> 4006 4013 4015 4006 4013 4009 4003 4011 4011 4017 4015 4008 4005 >>>>>>>> 3998 4000 >>>>>>>> 4002 4011 4012 4010 4013 4009 4010 4010 4010 4010 4011 4008 4007 >>>>>>>> 4007 4007 >>>>>>>> 4013 3998 4006 4007 4003 3999 4009 4005 4013 4018 4019 4014 4012 >>>>>>>> 4003 4008 >>>>>>>> 4010 4017 3999 4002 4008 4008 4008 4004 4010 4008 3996 4002 4009 >>>>>>>> 4014 4011 >>>>>>>> 4012 4006 4007 4004 4000 4008 4008 4010 4008 4007 4006 4003 4007 >>>>>>>> 4000 4008 >>>>>>>> 4003 4010 4003 4006 4006 3996 4001 4003 4000 4002 3996 4007 4003 >>>>>>>> 4011 4013 >>>>>>>> 4012 4017 4013 4008 4002 4010 4005 4013 4016 4014 4012 4015 4013 >>>>>>>> 4013 4007 >>>>>>>> 4011 4008 4010 4014 4016 4016 4015 4018 4013 4016 4005 3997 4007 >>>>>>>> 3998 4007 >>>>>>>> 4002 4004 4009 4007 4010 4010 4001 4005 4008 4003 4010 4012 4013 >>>>>>>> 4006 3994 >>>>>>>> 4014 4006 4008 4009 4014 4015 4012 4012 4013 4010 4012 4014 4015 >>>>>>>> 4020 4017 >>>>>>>> 4017 4013 4010 4020 4014 4012 4010 4008 3997 4002 4001 4012 4010 >>>>>>>> 4006 4016 >>>>>>>> 4010 4004 4004 4004 4003 4004 4004 3999 4003 4007 4008 4006 4005 >>>>>>>> 4006 4007 >>>>>>>> 4013 4013 4011 4010 4010 4005 3996 4002 4008 4012 4012 4007 4006 >>>>>>>> 4000 3999 >>>>>>>> 4009 4005 4013 4010 4008 4012 4011 4015 4016 4017 4013 4009 4008 >>>>>>>> 4007 4006 >>>>>>>> 4015 4012 4010 4013 4011 4016 4012 4013 4012 4009 4007 3998 3995 >>>>>>>> 3998 4004 >>>>>>>> 4003 4011 4009 4001 3998 4007 4008 4001 4008 4008 4012 4013 4007 >>>>>>>> 3998 3999 >>>>>>>> 4015 4007 3997 4005 4009 4007 4002 4009 4015 4012 4007 4009 4013 >>>>>>>> 4017 4015 >>>>>>>> 4010 4005 4011 4017 4015 4010 4013 4012 4004 4008 4012 4010 4014 >>>>>>>> 4015 4013 >>>>>>>> 4016 4016 4016 4007 4009 4011 4010 4009 4010 4010 4004 4004 4002 >>>>>>>> 4002 4011 >>>>>>>> 4008 4007 4004 4010 4006 4008 4007 4005 4006 4008 4002 4009 4013 >>>>>>>> 4011 4006 >>>>>>>> 4010 4015 4014 4016 4018 4015 4017 4015 4015 4018 4016 4013 4011 >>>>>>>> 4013 4016 >>>>>>>> 4017 3998 4012 4006 4008 4014 4011 4003 4012 4018 4014 4012 4005 >>>>>>>> 3994 4000 >>>>>>>> 4004 4003 4007 4012 4012 4005 4005 4006 4008 4001 3999 4004 4000 >>>>>>>> 4004 4000 >>>>>>>> 4011 4010 4005 4002 4009 4007 4002 4013 4015 4020 4012 4011 4011 >>>>>>>> 4002 4011 >>>>>>>> 4008 4013 4009 4012 4006 4011 4009 4015 4013 4009 4003 4008 4003 >>>>>>>> 4005 4009 >>>>>>>> 4017 4001 4010 4012 4009 4009 4007 4010 4007 4006 4004 4003 4008 >>>>>>>> 4008 4003 >>>>>>>> 4012 4009 4007 4008 4005 4006 4000 3995 4000 4007 4006 4003 4004 >>>>>>>> 4009 4004 >>>>>>>> 4008 4020 4010 4009 4006 4008 4015 4018 4017 4011 4014 4013 4010 >>>>>>>> 4009 4012 >>>>>>>> 4011 4009 4016 4017 4016 4011 4005 4007 4012 4014 4014 4005 4004 >>>>>>>> 3998 4000 >>>>>>>> 4009 4009 4005 3996 4006 3999 4002 4009 4014 4011 4009 4008 4008 >>>>>>>> 4012 4013 >>>>>>>> 4003 4007 4010 4012 4012 4010 4010 4010 4014 4017 4016 4007 4020 >>>>>>>> 4013 4007 >>>>>>>> 4019 4015 4014 4016 4016 4016 4009 4004 4000 4009 4012 4010 4015 >>>>>>>> 4015 4015 >>>>>>>> 4016 4011 4013 4008 4012 4009 4007 4006 4005 4006 4012 4004 4011 >>>>>>>> 4015 4009 >>>>>>>> 4010 4014 4004 3998 4008 4010 4004 4003 4008 4013 4013 4009 4007 >>>>>>>> 4004 4009 >>>>>>>> 4014 4013 4016 4012 4010 4011 4013 4013 4013 4008 4017 4015 4015 >>>>>>>> 4011 4014 >>>>>>>> 4016 4007 4013 4014 4009 3999 4008 4003 4005 4009 4014 4007 4003 >>>>>>>> 3993 3999 >>>>>>>> 3999 4005 4013 4003 4011 4009 4011 4010 4006 4002 4006 3998 4001 >>>>>>>> 4003 4009 >>>>>>>> 4011 4011 4016 4013 4018 4013 4010 4003 4000 4006 4015 4011 4017 >>>>>>>> 4017 4016 >>>>>>>> 4010 4017 4017 4016 4012 4016 4015 4013 4012 4013 4009 4003 4010 >>>>>>>> 4006 4012 >>>>>>>> 4004 4013 4001 4000 4005 3997 4004 4008 4012 4008 4005 3996 4003 >>>>>>>> 3999 4006 >>>>>>>> 4016 4002 4000 4002 4008 4009 4006 3995 4005 4008 4013 4012 4012 >>>>>>>> 4009 4007 >>>>>>>> 4013 4006 4018 4012 4005 4016 4014 4012 4011 4007 4014 4016 4015 >>>>>>>> 4014 4013 >>>>>>>> 4005 4007 4013 4008 4009 4002 4012 4011 4015 4013 4012 4010 4004 >>>>>>>> 4007 4005 >>>>>>>> 4013 4008 4013 4014 4014 4004 4012 4012 4012 4007 4009 4006 4010 >>>>>>>> 4013 4014 >>>>>>>> 4015 4006 4008 4009 4007 4004 4011 4005 4009 4007 4020 4015 4012 >>>>>>>> 4005 4008 >>>>>>>> 4021 4018 4016 4013 4003 4015 4015 4019 4014 4013 4003 4007 4009 >>>>>>>> 4014 4015 >>>>>>>> 3999 4016 4007 4008 4004 4008 4011 4003 4011 4012 4009 4006 4009 >>>>>>>> 4008 4005 >>>>>>>> 4002 4005 4011 4008 4011 4009 4016 4014 4010 4012 4016 4015 4011 >>>>>>>> 4010 4009 >>>>>>>> 4010 4011 4019 4018 4015 4017 4010 4000 4009 4015 4017 4017 4013 >>>>>>>> 4017 4012 >>>>>>>> 4011 4016 4014 3999 4008 4006 4006 4011 4010 4001 4000 4008 3998 >>>>>>>> 4007 4013 >>>>>>>> 4008 4007 4011 4008 4011 4007 4013 4012 4014 4009 4006 4006 4007 >>>>>>>> 4000 4002 >>>>>>>> 4012 4011 4008 4010 4004 4015 4013 4015 4014 4006 4019 4012 4007 >>>>>>>> 4016 4016 >>>>>>>> 4005 4009 4011 4010 4010 4004 4013 4014 4015 4015 4016 4011 4014 >>>>>>>> 4009 4004 >>>>>>>> 4015 4013 4009 4011 4009 4009 4006 4008 4005 3995 4001 4007 4007 >>>>>>>> 4008 4008 >>>>>>>> 4008 4008 4004 4006 4011 4010 4002 4011 4013 4009 4003 4000 4006 >>>>>>>> 4011 4010 >>>>>>>> 4015 4020 4016 4017 4017 4016 4016 4015 4014 4013 4010 4012 4006 >>>>>>>> 4002 4000 >>>>>>>> 4017 4016 4013 4010 4013 4008 4011 4010 4006 4002 4007 4009 4010 >>>>>>>> 4011 4007 >>>>>>>> 4011 4012 4014 4003 4003 4012 4010 4014 4013 4010 4007 3994 4000 >>>>>>>> 4006 4002 >>>>>>>> 3999 4006 4004 4008 4011 4005 4005 4010 4008 4012 4014 4017 4015 >>>>>>>> 4015 4001 >>>>>>>> 4011 4006 4015 4017 4013 4015 4014 4018 4016 4012 4011 4009 4011 >>>>>>>> 4014 4015 >>>>>>>> 4008 4009 4009 4006 4011 4010 4008 4010 4005 4006 4005 4005 4009 >>>>>>>> 4003 4009 >>>>>>>> 4008 4010 4011 4010 4012 4007 4009 4007 4000 4004 4008 4008 4013 >>>>>>>> 4016 4017 >>>>>>>> 4019 4016 4021 4018 4018 4012 4009 4007 4015 4015 4012 4013 >>>>>>>> >>>>>>>> real 0m0.328s >>>>>>>> user 0m0.010s >>>>>>>> sys 0m0.250s >>>>>>>> >>>>>>>> >>>>>>>> That's actually not too bad for opening, and closing the file 1000 >>>>>>>> iterations, then using printf() to display the data to stdout. So, >>>>>>>> looks >>>>>>>> like 328ms for 1000 iterations on the same adc channel. >>>>>>>> >>>>>>>> debian@beaglebone:~$ uname -a >>>>>>>> Linux beaglebone 4.1.5-ti-rt-r10 #1 SMP PREEMPT RT Fri Aug 14 >>>>>>>> 00:02:42 UTC 2015 armv7l GNU/Linux >>>>>>>> >>>>>>>> debian@beaglebone:~$ cat /etc/dogtag >>>>>>>> BeagleBoard.org Debian Image 2015-03-01 >>>>>>>> >>>>>>>> Meaning Wheezy 7.8, and systemd disabled - if the later maters at >>>>>>>> all. >>>>>>>> >>>>>>>> >>>>>>> -- >>>>>> 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] <javascript:>. >> 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.
