Hi, I hope anyone can lend me a hand with this.
I have to desing a full duplex 32bit I2S to USB bridge.
It has to be stereo in/stereo out with no process more than taking signal from and ADC and sending it to USB and taking signal from USB and sending it to a DAC.
I was thinking in using a XU208 due to the small footprint and cost, I've seen commercial boards but only have I2S output. It has been a little hard finding a reference circuit to be based on. Here I have some questions.
1) Do you think the XU208 is adequate for the task?
2) Do the XU208 generates the necessary clock signals? because I've seen desing with extra 49.152Mhz and 45.1584Mhz and also with half of that, and that gives me uncertainties.
Any other thought is welcome. Thank you!
AUDIO INTERFACE XU208 DESIGN
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Just don't pay much attention to cheep DACs with no name. They're not good enough by design, but advertised as a high-end. Although they have made good progress in recent years. Never mind. It makes more sense to check the official XMOS EVBs and documentation. There are also many well-designed professional audio interfaces based on XMOS. In particular, the XU208 was a popular MCU for low-cost audio interfaces with CS4270/4272 codec. I saw a lot of it. For example, PreSonus Studio 26. They used PL611-01 low cost general purpose frequency synthesizers, not 49.152Mhz and 45.1584Mhz XOs. Also I like desing and sound of first generation of MOTU M2/M4 with XMOS and PL611-01 inside. Though MOTU still has some issue with a clock change in the firmware.
In our ADC/DAC products we used XMOS MCUs with Skyworks (SiLabs) clock generator (programmable in real-time with our custom made library) and very customised firmware. 3 times bigger compared to the original. Back in the days the original source code for XS1/XS2 generation was not perfect. USB3.0 compatibility issues, cracks/pops on start/stop playback, lack of 24 bit register support and so on. Fortunately, many of these issues have been fixed by XMOS engineers in the latest audio source sample/libraries. That's why I strongly recommend using the latest XMOS MCU generation XS3 and the latest code sample with complicated enough fixes. With the new XMOS generation, you can start from scratch with no issues. Also XS3 MCU finally has an internal programmable audio PLL, that looks very promising for mass-market.
Don't be surprised. Just to do a flawless 2ch ADC and DAC conversion takes many years of R&D by highly educated engineers. I would recommend to forget about 2 days for copying and pasting some "reference" design. It's good as a starting point.
In our ADC/DAC products we used XMOS MCUs with Skyworks (SiLabs) clock generator (programmable in real-time with our custom made library) and very customised firmware. 3 times bigger compared to the original. Back in the days the original source code for XS1/XS2 generation was not perfect. USB3.0 compatibility issues, cracks/pops on start/stop playback, lack of 24 bit register support and so on. Fortunately, many of these issues have been fixed by XMOS engineers in the latest audio source sample/libraries. That's why I strongly recommend using the latest XMOS MCU generation XS3 and the latest code sample with complicated enough fixes. With the new XMOS generation, you can start from scratch with no issues. Also XS3 MCU finally has an internal programmable audio PLL, that looks very promising for mass-market.
Don't be surprised. Just to do a flawless 2ch ADC and DAC conversion takes many years of R&D by highly educated engineers. I would recommend to forget about 2 days for copying and pasting some "reference" design. It's good as a starting point.
Last edited by MaximLiadov on Mon Jan 13, 2025 7:05 am, edited 1 time in total.
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Thanks so much for your feedback it gives me a clearer idea to continue. I've been working with this project for more than a year, I tryes ESP32 and STM32, but either their USB or audio capability was not enough, I have already made this project in 24 bits succesfully but I am requiere the 32 bit for the great S/N ratio and headroom.Thanks again and I will take a look at all what you sent me.