Re: [beagleboard] Reading analog inputs fast in beaglebone black
I need to read all 7 analog pins in the BBB every 5 milliseconds. I'm
doing so with the following C code:
...
while(1){
fread(value_str, 6, 6, f0);
value_int = strtol(value_str,NULL,0);
printf(0 %li\n, value_int);
fflush(stdout);
usleep(5000);
rewind(f0);
}
Hoever, the cpu usage goes up really high (20%). Is there any way to
read the analog inputs differently so that it doesn't use as much CPU?
I would replace printf(0 %li\n, value_int); fflush(stdout); by
saving the converted values into an array, and print the values only
when the measurement ist finished.
Someone suggested DMA but I'm completely lost on that regard...
That would be for specialists
Christian
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Re: [beagleboard] Reading analog inputs fast in beaglebone black
I would replace printf(0 %li\n, value_int); fflush(stdout); by saving the converted values into an array, and print the values only when the measurement ist finished. What do you mean when the measurement is finished? I need to read the inputs every 5 milliseconds forever. Is there a ready flag or a time to wait after reading the file? Thanks. -- 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.
Re: [beagleboard] Reading analog inputs fast in beaglebone black
Christian is correct. Don't use printf. It introduces a significant overhead. remove printf, copy into a variable. Then check and see if you can meet timing. *fingers crossed* Your email mentioned you wanted to acquire all 7 analog inputs for real time audio every 5ms. Depending on your level of processing of the audio, you might face difficulty with that. Who knows, might just work. Is there any correlation regarding timing between the channels? Can you acquire a sample from channel 1, sleep 500ms, acquire from channel 2, sleep 500ms acquire from channel 3, Or do all samples have to be acquired simultaneously? ZubairLK On Saturday, May 24, 2014 3:23:53 PM UTC+1, Rafael Vega wrote: I would replace printf(0 %li\n, value_int); fflush(stdout); by saving the converted values into an array, and print the values only when the measurement ist finished. What do you mean when the measurement is finished? I need to read the inputs every 5 milliseconds forever. Is there a ready flag or a time to wait after reading the file? Thanks. -- 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.
Re: [beagleboard] Reading analog inputs fast in beaglebone black
From: Rafael Vega email.r...@gmail.com
Reply-To: beagleboard@googlegroups.com
Date: Saturday, May 24, 2014 at 1:23 AM
To: beagleboard@googlegroups.com
Subject: [beagleboard] Reading analog inputs fast in beaglebone black
I need to read all 7 analog pins in the BBB every 5 milliseconds. I'm doing so
with the following C code:
void main(){
char value_str[7];
long int value_int = 0;
FILE* f0 = fopen(/sys/bus/iio/devices/iio:device0/in_voltage0_raw, r);
while(1){
fread(value_str, 6, 6, f0);
value_int = strtol(value_str,NULL,0);
printf(0 %li\n, value_int);
fflush(stdout);
usleep(5000);
rewind(f0);
}
Hoever, the cpu usage goes up really high (20%). Is there any way to read the
analog inputs differently so that it doesn't use as much CPU? Someone
suggested DMA but I'm completely lost on that regard...
You should try the IIO driver which you will find under
/driver/IIO/adc/ti_am335x_adc.c. Samples are stored in a buffer which you
can read with a user space app.
Search github for IIO and you will find several user space examples on how
to use IIO.
Regards,
John
Any help will be appreciated.
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Re: [beagleboard] Reading analog inputs fast in beaglebone black
From: Rafael Vega email.r...@gmail.com
Reply-To: beagleboard@googlegroups.com
Date: Saturday, May 24, 2014 at 1:23 AM
To: beagleboard@googlegroups.com
Subject: [beagleboard] Reading analog inputs fast in beaglebone black
I need to read all 7 analog pins in the BBB every 5 milliseconds. I'm doing so
with the following C code:
void main(){
char value_str[7];
long int value_int = 0;
FILE* f0 = fopen(/sys/bus/iio/devices/iio:device0/in_voltage0_raw, r);
while(1){
fread(value_str, 6, 6, f0);
value_int = strtol(value_str,NULL,0);
printf(0 %li\n, value_int);
fflush(stdout);
usleep(5000);
rewind(f0);
}
Hoever, the cpu usage goes up really high (20%). Is there any way to read the
analog inputs differently so that it doesn't use as much CPU? Someone
suggested DMA but I'm completely lost on that regard...
Here is some additional info on IIO that might be helpful:
http://processors.wiki.ti.com/index.php/AM335x_ADC_Driver%27s_Guide
Regards,
John
Any help will be appreciated.
--
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