I have a requirement to mix Analog line-in audio with two I2S audio sources and output simultaneously as I2S and analog line-out audio. Any suggestion please? Pl refer to the attached file for details. Thanks
Since you have two I2S lines it makes this more complicated. We have several small DSP products that can take an analog signal and an I2S/TDM signals and sum them in a small DSP and then send it out to an on-chip DAC and out of the serial port. However, there is only one serial port on these parts and you will need two ports.
So in that case you will need to jump up to the ADAU1446 (the lowest cost DSP in the ADAU1442 family). This part has many serial ports. Then you will have to use a codec for the ADCs and the DACs. Look up the price and performance of these parts. Some may have features you need for your application. The ADAU1361, the AD1938 or the 1939 and the ADAU1372 may also work well for you.
However, using this DSP to only sum is kind of like using a shotgun to kill a fly.
If you can tolerate two conversions you could use two of either the ADAU1701, the ADAU1761 or the ADAU1772 to take in the analog audio and sum it with the stereo I2S signal. Then send it out of the DAC. Then take the analog summed signal and send it to the second SigmaDSP and there convert it and sum it with the mono I2S signal and then send it out both the DAC and the serial port. So study the costs of these two options.
There is one more part, the ADAU1373 that will do what you want. It is a much more complicated part and it is a wafer level part as well. I am not sure how long this part will be in production so that is another factor. So far I think the ADAU1446 along with an ADAU1372 codec would probably be the simplest and most cost effective solution for you.
Let me know what other design constraints you have and I would be glad to continue assisting in your parts selection.
Thanks you very much for your detailed reply. I have a doubt, if two conversion is used, will the quality of signal won't degrade?
Anyhow, this design is still under study and we are looking at various options and solutions. I'll let you know for the requirement once the design is freeed.
Yes, the audio quality will certainly degrade. Since I know nothing of your application I feel the need to mention it as an option. Some applications do not require very high quality audio so this would certainly work. This is why I do not like the solution but it is a solution that may work for some applications.
Let me know if you require more information.
Thanks again, the project is still in preliminary stage, I will share more info once things are firm on my side.
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