Need help on RPi I2S audio

[blueskull]

Hi,

I'm working on a RPi based audio analyzer, which requires simultaneous playback and record at 24bit 192ksps.
I used BCM2708-I2S module, and I wrote my own audio machine definition and codec definition.
My own driver works fine if I only declare the playback interface. When I tried to declare recording interface or both, the module won't be started.
Here is the problem: "bcm2708-i2s 3f203000.i2s: missing DMA channel for stream: 1".
I modified the driver from /sound/soc/bcm/rpi-dac.c and rpi-proto.c, as well as /sound/soc/codecs/pam1794a.c and wm8804.c.
Also, I referred to Cirrus Logic's audio HAT's driver, and did not spot too many different.
I derived my device tree descriptor file from rpi-dac's as well as Cirrus Logic's.

So far, no progress. Any thoughts?




Thanks,
Bo

[diyaudio]

This sounds like a very esoteric problem, interesting project. is it an audio spectrum analyser?   

[diyaudio]

This sounds like a very esoteric problem, interesting project. is it an audio spectrum analyser?

It is an audio analyzer I designed to measure DAC IMD, THD and DR, down to -130dB, -130dB and 140dB.
At this level, no ADC/DAC chips are perfect, so lots of analog filters are used.
I am now using a CS5381 to sample incoming data, and using a AD1955 to generate calibration signal.
THD and IMD as well as DR measurement paths are freshly calibrated before every measurement.
The calibration of ultra low THD/IMD/DR with limited non-ideal parts are documented in some TI's and LT's data sheets and app notes.

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In this case, I just want a 24/192 IO card, while RPi's integrated I2S seems to be the cheapest, even cheaper than am XMOS card. Most cheap XMOS cards do not have digital input capability.
As usual, this will be an open source project. Since this forum is not audiophile friendly, I decided to finish it first before publishing it here.
I can PM you the current design documents if you are interested in it.

sounds interesting, PM me..