How to use I2S as input/output  in Sigma Studio 3.13

Hi,

 i am a new user in Sigma Studio . my EV board is using ADAU1701 .

i will use I2S instead of ADC input .

my question is  :

1. how can i enable and select I2S as input ?

2. how can i convert the in input 16bit 44.1Khz sample to 24bit 88.2KHz ?

thx a lot .

br

Charles

Parents
  • 0
    •  Analog Employees 
    on Nov 3, 2016 11:52 PM

    Hello Charles,

    I have attached the user guide that details how to use the serial ports for an I2S signal. You can find it on page 5 under the heading "External Digital Input". This shows you how to set the registers up and also where the signal show up in the SigmaStudio schematic.

    Regarding the conversion of the sample rate. This part does not have a sample rate converter built in. If you do need to convert then you will have to use an ADAU1442 or an ADAU1452. These parts do not have converters built in so you would need a codec to handle the ADC and DAC conversions.

    If you are taking in this digital audio to go out to another system at 88.2KHz then that will also not work because the serial input and output ports have to run at the same rate in this part. If you are only wanting to go from 44.1kHz up to 88.2kHz to process inside the DSP and then go out of the DAC then you need to reevaluate why you want to do this. Taking a 16 bit signal and converting it to 24 bits will add the extra 8 bits but they will be interpolated so there is no way to bring back anything that was not there. In the frequency domain, taking a 44.1kHz signal and up-sampling it to 88.2KHz will not give you any more frequency response. Frequencies above 22.05kHz were removed when it was originally sampled and cannot be reconstructed. Then you will be using the DSP at a much higher rate reducing the amount of instructions you can process in a sample period. So you do not gain resolution and you lose instructions. So run at 44.1kHz and it will sound fine.

    Now, if you are only coming in from the ADC, to the DSP then to the DAC then you will get better resolution running at 88.2kHz. This is because you are actually sampling at that rate.

    Thanks,

    Dave T

    EVAL-ADAU1701MINIZ.pdf
Reply
  • 0
    •  Analog Employees 
    on Nov 3, 2016 11:52 PM

    Hello Charles,

    I have attached the user guide that details how to use the serial ports for an I2S signal. You can find it on page 5 under the heading "External Digital Input". This shows you how to set the registers up and also where the signal show up in the SigmaStudio schematic.

    Regarding the conversion of the sample rate. This part does not have a sample rate converter built in. If you do need to convert then you will have to use an ADAU1442 or an ADAU1452. These parts do not have converters built in so you would need a codec to handle the ADC and DAC conversions.

    If you are taking in this digital audio to go out to another system at 88.2KHz then that will also not work because the serial input and output ports have to run at the same rate in this part. If you are only wanting to go from 44.1kHz up to 88.2kHz to process inside the DSP and then go out of the DAC then you need to reevaluate why you want to do this. Taking a 16 bit signal and converting it to 24 bits will add the extra 8 bits but they will be interpolated so there is no way to bring back anything that was not there. In the frequency domain, taking a 44.1kHz signal and up-sampling it to 88.2KHz will not give you any more frequency response. Frequencies above 22.05kHz were removed when it was originally sampled and cannot be reconstructed. Then you will be using the DSP at a much higher rate reducing the amount of instructions you can process in a sample period. So you do not gain resolution and you lose instructions. So run at 44.1kHz and it will sound fine.

    Now, if you are only coming in from the ADC, to the DSP then to the DAC then you will get better resolution running at 88.2kHz. This is because you are actually sampling at that rate.

    Thanks,

    Dave T

    EVAL-ADAU1701MINIZ.pdf
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