Hi we fi
So how did it end up for you? I am having similar problem, would you care
posting your solution?
Regards
Hernando
On Monday, November 25, 2013 12:19:19 PM UTC+1, fe wi wrote:
>
> Hi!
>
> I am currently using my Beaglebone Black with the following KERNEL:
> 3.8.13xenomai-bone28.1 (including the ti_am335_adc driver).
>
> Part of my Project is reading signals from an ADC and then processing
> them. I would love to use the onboard ADC for that, but I require to sample
> 5 channels @ 2 kHz each. (I have installed the Xenomai Kernel mainly for
> processing purposes but it might be useful for sampling as well ;) )
>
> My first simplistic try was to just read the voltage values from the files
> provided in "/sys/bus/iio/devices/iio:device0/in_voltage0_raw" .
> This works fine so far, but is just not fast enough. ( I get about 500 sps
> on ONE channel)
>
> Here is that part of my CODE:
> for(;;) {
>
> rt_task_wait_period(NULL); // Xenomai
>
> now=rt_timer_read(); // Xenomai
>
> // Work for the current period //
>
> FILE *read = fopen (
> "/sys/bus/iio/devices/iio:device0/in_voltage0_raw", "r");
>
>
> fscanf (read, "%f", &value);
> float voltage = value * (1800.0/4095.0);
> fprintf (write, "Value: %f Voltage: %f\n", value, voltage);
>
> printf("Time since last turn: %ld,%06ld ms Value:%f
> Voltage:
> %f\n",
> (long)(now - previous) / 1000000,
> (long)(now - previous) % 1000000, value, voltage);
> previous = now;
>
> fclose ( read );
> fclose ( write );
>
> }
> (I know that leaving out the printf part and the voltage calculation
> increases performance, but still not enough)
>
> Is there any other way reading the values, directly from the memory
> location or a register? Perhaps using mmap?
> Or is there a Xenomai function for reading from an iio device? (I couldn't
> find any...)
>
> I have seen two interesting links about continuous sampling:
> -
> http://beagleboard-gsoc13.blogspot.de/2013/07/sampling-analogue-signals-using-adc-on.html
> - http://processors.wiki.ti.com/index.php/AM335x_ADC_Driver%27s_Guide
>
> But i can't get the generic_buffer.c from those sites to work correctly
> (as the trigger handling seems to be outdated), plus i might need to know a
> kind of "oneshot" read function anyway to mux the 5 channels i want to
> sample. Or is it possible to continuous sample multiple channels? The
> Driver guide says 'no', but the Author from the other link seems to have
> worked a lot on the adc Driver since.
>
> I am currently trying to figure out the code in generic_buffer.c and the
> used iio_utils.h and the adc driver, but it is a lot of code and drivers
> are not my strong suit.
> So far I think I need to setup the ADC to my needs (somewhat similar to
> generic_buffer.c) and then read from it somehow, but I am really struggling
> with that!
>
>
> So now you know the state of my project :) but to *sum it up*:
>
> Are my demands (5 channels @ 2 kHz) even possible using only the on-board
> ADC?
> And if yes how do i read the values fast enough? Any tips?
>
> Thank you in advance!!
>
>
>
--
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/groups/opt_out.
