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DSD audio IO

Question asked by Borge Strand-Bergesen on Mar 21, 2019
Latest reply on Mar 25, 2019 by Yuri Muhin



I'm looking at various audio interfaces for the RT1015 and similar. While I2S is very common, there is increasing demand for two-bit serial interfaces to DAC chips. 


There are at least two interfaces which use separate data lines for L and R audio data (not time multiplexed like I2S), and I'm curious if they can be supported with the built-in series interfaces of i.MX crossover MCUs. 


DSD in particular uses a shared bit clock and separate L and R data pins. The data words are one bit long so no word clock is involved. L and R data pins must be in sync. The data typically arrives in a packaged structure over USB and must be sorted by sequencial code and inserted into some buffer which can be fed to the series interfaces by internal DMA. Other than the lack of word clock and the two synchronous data lines, this is very close to USB -> I2S. 


A similar format is named "raw" or "no-oversampling" in DAC terminology. There, separate L and R data pins share a bit clock and a word clock. Word length is typically 24-bit and can be left-justified or right-justified. Even closer to I2S with the presence of a word clock there, but the two-bit data interface is quite different. 


I'm using an AVR32 today and looking for alternatives. Having IO which can do this without external logic will be an important part of that decision. 


All the best,