Re: iio and jack - 1MHz sample rate success

[Matt Flax <flatmax@flatmax.org>]

On 14/02/14 11:47, Christian Gagneraud wrote:
> On 12/02/14 20:36, Matt Flax wrote:
>>
>> I have implemented the jack2 iio driver and have done a couple of tests.
>>
>> In a preliminary finding, waiting for more time to test and re-test, I
>> have had success.
>> I don't see any overruns reported (when setup properly), and I haven't
>> put a signal through the system to highlight any un-reported overruns.
>> Next week I will look into this more.
>
> Hi Matt,
>
> This is a very interesting usage of the linux-iio framework. Can you 
> say a bit more about your analog front-end? Did you use an audio IC, 
> or SPI/I2C ADC? If so which one.
>

Thank you,

The chips were AD7476A chips, so an SPI bus. There was hardware level 
and kernel level support from Lars-Peter Clausen and Alexandru Tofan.

Matt

> Thanks,
> Chris
>
>
>>
>> Firstly I would like to say that writing a driver for jack2 is a little
>> difficult because there is not much documentation ... at least I
>> couldn't find simple information. Some inline src doc would be good ...
>> mind you, I could have put more into my driver as well :)
>>
>> On the system with IIO devices I ran :
>> jackd -iio
>>
>> I then setup and ran netjack on both computers.
>>
>> On the other computer I used :
>> jack_capture -c 2 -p system:capture*
>>
>> ... wahlah ... it worked ! with an MTU of 1500. Thats 2 channels @ 1 MHz
>>
>> Everything reporting 1MHz sample rates and so on a so forth, no xruns
>> and the wav file looked like what I expected ...
>>
>> When I tried to record 4 channels @ 1 MHz, I had to increase the MTU to
>> 6000 to get rid of xruns on the ARM core. But still ... 4 channels @
>> 1MHz over a network ... pretty good start !
>>
>> I would like to integrate my both of my iio branchs into the jack1 and
>> jack2 repos, but for now I have forked the jack2 repo here :
>> https://github.com/flatmax/jack2/tree/iio
>>
>> I have some questions for other developers of jack2.
>> is it necessary to use :
>>      JackDriver::CycleTakeBeginTime();
>> and
>>      JackDriver::CycleTakeEndTime();
>>
>> ?
>>
>> thanks
>> Matt
>> p.s. Don't forget that these findings are very preliminary and things
>> need to be neatened up, debugged more and so on and so forth.
>>
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