Dear William,
Amazing, i m awed by your rigorous treatment of the topic :-) and as you
said I ran a test of that program, which proved that you are correct!! the
program ( mine one) is taking 10.2% to 11% of CPU!! which proves that its
in blocking mode.
and I am not aware of O_NONBlOCK and mmap.. I will read it up and see but
for that do you recommend and preferred resources?
and thanks for the code I will run it and let you know. but there are few
hick ups:
1. My *uname -a out put is : *Linux beaglebone 3.8.13-bone72 #1 SMP Tue Jun
16 21:36:04 UTC 2015 armv7l GNU/Linux
2. your kernel has preemption i.e.. it is RT patched / enabled: mine is
not!!
*So are you using official Debian image & patched it or r you using some
other image?*
3. I dont know how to turn off systemd?
can you guide me!!
Once again thanks a LOT!! :-)
On Wednesday, September 30, 2015 at 11:11:34 AM UTC+5:30, William Hermans
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 beagleboard+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
