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I will be using an i2s codec with my 21065L, however I have some questions regarding the i2s protocol in the dsp. First, the dsp does not have any way to differentiate between the left and right channels received and/or transmitted, since an interrupt is generated for every word received and/or transmitted (no matter if left or right), and the application must demultiplex both channels properly. That means that if for some reason we lose a sample from either channel, maybe we will be reading next the left and right channels swapped by error. The obvious solution is to know the state of the L/R frame signal, but it is a reliable method at 96 KHz stereo sampling rate? It would be advisable to use another protocol (dsp, right-justified, etc.) to certainly aquire the left and right channels without errors of swapping them?. Thank you very much for any help. |
Understanding i2s codecs format
Started by ●January 24, 2005
Reply by ●January 24, 20052005-01-24
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I think you are right if you are just using interrupts without DMA. If you
use the DMA it can start on the left channel and interrupt every two samples (L+R). Go to the adsp archive and you will find that this has been discussed in the past. As I recall, early 21065L also had an I2S problem. Check the errata if you are using old parts. Al Clark Danville Signal Processing, Inc. -------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com At 10:17 PM 1/23/2005, jcarlosmor wrote: >I will be using an i2s codec with my 21065L, however I have some >questions regarding the i2s protocol in the dsp. > >First, the dsp does not have any way to differentiate between the >left and right channels received and/or transmitted, since an >interrupt is generated for every word received and/or transmitted (no >matter if left or right), and the application must demultiplex both >channels properly. That means that if for some reason we lose a >sample from either channel, maybe we will be reading next the left >and right channels swapped by error. The obvious solution is to know >the state of the L/R frame signal, but it is a reliable method at 96 >KHz stereo sampling rate? It would be advisable to use another >protocol (dsp, right-justified, etc.) to certainly aquire the left >and right channels without errors of swapping them?. > >Thank you very much for any help. |
