Trying to read data from accelerometer buffer

Trying to read data from accelerometer buffer

[Ibrahim Mattus Neto]

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Re: Trying to read data from accelerometer buffer

[Jonathan Cameron]

On 29/10/15 10:05, Ibrahim Mattus Neto wrote:
> Hi, I am having issues reading from a accelerometer and I hope yo
> might help me (if I should ask this question elsewhere, please tell
> me)
> 
> What I am trying to do is get data from a buffer (I am using the
> source code from iio_readdev as an example) but I can't figure it out
> how to interpret the data properly.
A quick google suggests this is from libiio.  Perhaps Paul or Lars
can give more detail.
> 
> I was expecting to get a bunch of numbers related to the X axis but
> when it writes to stdout I get a bunch of weird characters, here is
> the output:
> 
> @������@������������������������������������������������
> 
> How can I get values of x, y and z axes?
The data is in binary, whereas piping it to stdout is presumably going to expect
asci characters.   I would imagine, glancing at that example code
that it was meant for piping into some other program that actually interpreted
the stream?

Alternatively, take a look at tools/iio/generic_buffer.c in the kernel source
tree for an example of how to read from the buffers.
> 
> Is there anything else I should provide? Is there some information missing?
> 
> Thanks in advance!
> Ibrahim
> N�����r��y���b�X��ǧv�^�)޺{.n�+����{��*"��^n�r���z�\x1a��h����&��\x1e�G���h�\x03(�階�ݢj"��\x1a�^[m�����z�ޖ���f���h���~�mml==
> 

Re: Trying to read data from accelerometer buffer

[Ibrahim Mattus Neto]

Hi Jonathan,

Thank you for your time!

I read through libiio documentation and found what I was missing. It
was a matter of using 'iio_channel_convert'

Here is how I managed to get the data.

I used as a guide the file iio_readdev.c and changed the print_sample
function to:

static ssize_t print_sample(const struct iio_channel *chn, void *buf,
size_t len, void * d) {
/* Function called for each sample on buffer*/
    int16_t val;

    iio_channel_convert(chn, &val, buf);

    printf("Value of sample: %d", val);

    fflush(stdout);

    return len;
}

Thank you very much for your help!

Regards,
Ibrahim.

2015-10-31 8:29 GMT-02:00 Jonathan Cameron <jic23@kernel.org>:
> On 29/10/15 10:05, Ibrahim Mattus Neto wrote:
>> Hi, I am having issues reading from a accelerometer and I hope yo
>> might help me (if I should ask this question elsewhere, please tell
>> me)
>>
>> What I am trying to do is get data from a buffer (I am using the
>> source code from iio_readdev as an example) but I can't figure it out
>> how to interpret the data properly.
> A quick google suggests this is from libiio.  Perhaps Paul or Lars
> can give more detail.
>>
>> I was expecting to get a bunch of numbers related to the X axis but
>> when it writes to stdout I get a bunch of weird characters, here is
>> the output:
>>
>> @������@������������������������������������������������
>>
>> How can I get values of x, y and z axes?
> The data is in binary, whereas piping it to stdout is presumably going to expect
> asci characters.   I would imagine, glancing at that example code
> that it was meant for piping into some other program that actually interpreted
> the stream?
>
> Alternatively, take a look at tools/iio/generic_buffer.c in the kernel source
> tree for an example of how to read from the buffers.
>>
>> Is there anything else I should provide? Is there some information missing?
>>
>> Thanks in advance!
>> Ibrahim
>> N�����r��y���b�X��ǧv�^�)޺{.n�+����{��*"��^n�r���z� ��h����&�� �G���h� (�階�ݢj"�� � m�����z�ޖ���f���h���~�mml==
>>
>