Hi John,
Sorry for the late answer, I had hard time using the PRUs and I am now
going to use the IIO ADC driver, I am able to read the sample with the cat
command in /sys/bus/iio/devices/iio:device0/in_voltage3_raw
However I am not able to use Libiio in order to read data from a user space
application, I am reading (nil) instead of my data. Do you have any idea of
where does the problem comes from ?
Here is the code I am using in the user space :
#define _BSD_SOURCE
#define _GNU_SOURCE
#define _DEFAULT_SOURCE
#include <cdk/cdk.h>
#include <locale.h>
#include <pthread.h>
#include <stdbool.h>
#include <unistd.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#ifdef __APPLE__
#include <iio/iio.h>
#else
#include <iio.h>
#endif
struct iio_context *ctx;
struct iio_device *dev;
struct iio_channel *ch;
int main()
{
ctx = iio_create_default_context();
dev = iio_context_get_device(ctx, 0);
ch = iio_device_get_channel(dev, 3);
iio_device_attr_write_longlong(dev, "sample_rate", 100);
iio_channel_attr_write_double(ch, "scale", 1);
iio_channel_enable(ch);
char *a = iio_device_get_data(dev);
printf("%p\n", a);
iio_channel_disable(ch);
return 0;
}
Thanks
Pierrick
Le lundi 26 février 2018 16:46:11 UTC-5, john3909 a écrit :
>
> The IIO ADC driver can run at 800K samples per second. Here is the patch
> that made that possible.
>
> https://patchwork.kernel.org/patch/9391487/
>
> I can confirm that I have tested the driver at 800Ksps and it works fine
> as long as you have a proper low impedance source for each ADC channel. CPU
> utilization was about 5% if I recall and that was probably used by the iiod
> daemon, which I used to display the waveform on a remote Linux app.
>
> There is example code in the original Starterware for McSPI, which should
> work fine if you are using the PRU low level drivers.
>
> Regards,
> John
>
>
>
>
> On Feb 26, 2018, at 12:56 PM, [email protected] <javascript:> wrote:
>
> Thanks John,
>
> I am now working with the starterware_PRU but i did not find examples for
> using the McSPI with the PRU, do you think it will be hard to adapt the
> initial code to the PRU ?
> By the way, looking to the IIO driver documentation, it seems that for the
> AM335x chip the max sampling rate is only 200k samples per second which may
> not be enough :
> http://processors.wiki.ti.com/index.php/Linux_Core_ADC_Users_Guide ; am I
> right ?
>
>
> Thanks
>
> Pierrick
>
> Le lundi 19 février 2018 23:15:50 UTC-5, john3909 a écrit :
>>
>> Like I said, it was based on Starterware, so search Github for
>> starterware and you will see a project starterware_PRU. It does use the
>> mcspi, so it is not a bitbang implementation.
>>
>> Regards,
>> John
>>
>>
>>
>>
>> On Feb 19, 2018, at 7:33 PM, [email protected] wrote:
>>
>> Thanks John for you answer, I was quit busy last week so I worked on this
>> during the Weekend.
>>
>> Unfortunately, I was not able to find a project that is using the SPI and
>> I2C interface with the PRU, I only found this one :
>>
>> https://github.com/chanakya-vc/PRU-I2C_SPI_master/wiki/SPI-Master-Controller
>> But it is using bit banging for the SPI part and not using the on-board
>> pull-up resistors for the I2C part.
>>
>> Concerning the ADC, I'll have a loook at the UIIO drivers in the coming
>> days it seems that it meets my need in term of real-time acquisition.
>>
>> Regards,
>>
>> Pierrick
>>
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