Computing > Embedded Computing

Audio I2S and Raspberry

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luiHS:

Hi.

I am developing a product, which uses an RT1064 microcontroller for process tasks, and a Raspberry for playing video and audio.

As a sound amplifier I have chosen a STA369 chip that integrates 4 channels configurable as simple or bridged. I will use a 3 channel setup, two simple and one bridged. This chip is controlled by I2C, and the audio input is digital by I2S.

I have not done anything before using I2S, and the question is whether it is a standard port that can be used with any I2S device. It would be a matter of connecting the I2S output of Raspberry to STA369 and configuring the Raspberry so that the sound is output through I2S.

gamalot:
IIRC, There is no MCLK output on the I2S interface of the Raspberry Pi.

Jacon:

--- Quote from: gamalot on May 15, 2021, 11:17:39 am ---IIRC, There is no MCLK output on the I2S interface of the Raspberry Pi.

--- End quote ---
So, would you explain, how those countless HiFi I/O HATs for RasPi are working ?
For example, this one:
https://www.hifiberry.com/docs/data-sheets/datasheet-dac-adc-pro/

luiHS:

--- Quote from: gamalot on May 15, 2021, 11:17:39 am ---IIRC, There is no MCLK output on the I2S interface of the Raspberry Pi.

--- End quote ---

Thanks, I've been looking for information on that.

My question now is if that clock signal MCLK can be injected externally with an oscillator. I have seen schematics with the PCM5121 DAC for Raspberry, which use external oscillators by switching between two of them based on the sampling frequency.

In the STA369 the external clock frequency provided to the XTI pin must be a multiple of the input sampling frequency (fs).
According with the datasheet table may be these 6 values for sound sampled to 44.1Hz and 48Khz:

 576*fs, 128*fs,  256*fs, 384*fs,  512*fs,  768*fs

This means, for example, for 256*fs, 11.2896 Mhz for a sound sampled at 44.1Khz and 12.288 Mhz for a sound sampled at 48Khz. Both oscillators available from Mouser.

https://www.mouser.es/ProductDetail/Epson-Timing/SG-8018CE-122880M-TJHPA3?qs=%252B6g0mu59x7IJ%252BhMyNAL4Rw%3D%3D
https://www.mouser.es/ProductDetail/Epson-Timing/SG-8018CE-112896M-TJHPA3?qs=OTrKUuiFdkahoS5c5bbz0w%3D%3D

Jacon:
This thread:
https://www.raspberrypi.org/forums/viewtopic.php?t=8496
may be helpfull...

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