ADAU1701 analog input and I2S input select

Hello Gilles,

Sorry this post fell through the cracks and nobody gave you an answer.

If the PCM9211 is limited to 96 kHz fs then the ADAU1701 must also run at 96 kHz. You can bring in up to 8 channels into the 1701 using a TDM-8 data stream. If you only need two channels then it can be I2S into the serial port. This data will appear as sources 2&3 in the input block with 0 & 1 being the on-chip ADCs.

If you would like to run at 192 kHz then you can use one of our ADCs that can run at 192 kHz. The ADAU1978 is one and there are more depending on your application.

Please let me know if you have any new issues I can help with.

Dave T

Thank you Dave,

Two channels are enough for my application, I will try with signals up to 96kHz SR first.

My target is a microless hardware, the most simple digital circuit.

If need your support will be welcome.

Thank you again,

Gilles

Hello Gilles,

I took a look at the TI part to see what it is and get an idea of what you want to do. The part has a lot of features and I did not study the part in detail. Just make sure you can run it in the mode you need by just using pins to set the modes verses having to use I2C. The ADAU1701 can self-boot so I know that the ADI part can operate without a microcontroller.

The other detail is clocking. I did not see an ASRC function in the block diagram of the PCM9211. I see there is a PLL for locking to the incoming SPDIF clocks but I did not see a place where it will output a Master Clock (MCLK) for the rest of the system. If you are also planning on using a Bluetooth module then you need to define who is clocking who and understand that an SPDIF input is always a master for itself and usually it is wise to send it to an ASRC so it can adapt to the rest of the system's clocks. You do not want to run the system from an SPDIF input clock only. The jitter can be high and the clocks will come and go. Perhaps since they have a PLL it will free-run if it is getting no signal but then you will get jumps and discontinuities when it all of a sudden gets a clock input.

Now, we do have the ADAU1442/1445/1446 family of parts that have one built in SPDIF receiver and loads of ASRCs in with the DSP. You will need to have an external ADC/DAC and the Bluetooth module can interface to its numerous I2S serial ports. Then you can use the ASRCs for the Bluetooth module as well. This will allow you to run different parts at different sample rates. The ADAU1442 also has GPIO for external controls of the DSP functions.

So study your clocking scheme.

Thanks,

Dave T

HI Dave,

I looked at the ADAU1442 but the evaluation board is too expensive.

ADAU1701 works great for my application with analog input, I will study ASRC/digital input case later with the next update/upgrade.

The last point I have to solve is how to control the "voltage controlled delay" black with a potentiometer connected to the ADC input. I need to create a delay adjustable externally by the user from 0 to 0.5ms.

Your suggestions was appreciated.

Thanks GB

Hello Gilles,

Have at look at this document. It may help you with your question.

http://www.analog.com/media/en/technical-documentation/application-notes/AN-951.pdf

Dave T

Thank you Dave,

I read and test.

Best regards,

Gilles

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