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[DSP Add-On] DSP profile with SPDIF input

Andreas

January 02, 2022 19:31

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Hello,

I am using the DSP Add-on board and I have noticed that there is a SPDIF ipnut pin on one of the extension headers. I would like to use this as input source and do some crossover (so the 4way profile would be ideal). Can I use one of the example DSP profiles provided in the github repo? I found that some profiles have a 'channelSelectRegister'. Do I change the input source with this parameter? If so, how?

Are there some detailed descriptions of the sample profiles and their parameters?

Thank you!

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6 comments

• 0
  
  HiFiBerry team January 03, 2022 08:17

  You can't easily add an SPDIF input on the board. This not only requires another DSP profile, but also additional software on the Pi to generate clocks. This is a quite complicated setup. 
  
  While you can have a look at the DSP Add-on SigmaDSP project and DSP profile, there will be no support from us for this configuration.

• 0
  
  Andreas January 03, 2022 08:41

  Thanks for your answer.

  Is this the SigmaDSP project you mentioned? 

  https://github.com/hifiberry/hifiberry-dsp/blob/master/sample_files/dspproj/dsp-addon-v11.dspproj

  You mentioned the clock generation. Can you briefly describe how the clocks work in the standard case (input from Pi, not SPDIF)? Does the DSP chip generates the LRCK and BCK and the pi synchronise to these (since CK_out and CK_in are connected with each other on the board)?

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  Andreas January 07, 2022 06:52

  For those of you who want to do the same: I figured out that you can connect the SPDIF in pin (J3, pin 1) with the optical signal of your TV (having a toslink receiver). You can load the 4way-iir profile for example. The output will be on OUT0 (J3, pin 7) or OUT1 (J1, pin 2), which is dependent on the configuration of the DSP settings (see here e.g.). The I2S output can be connected with any amplifier.

  You do not need additional software on the pi for clock generation (in fact you do not need the pi at all except for loading the profiles with the DSP toolkit).

  I tested this setup with uncompressed optical stereo data.

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  HiFiBerry team January 07, 2022 08:17

  The setup that let's the DSP generate the clocks directly will only work correctly without the Pi. Otherwise you will have the Pi and the DSP generating clocks on the same clock lines independently which won't work correctly.

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  Andreas January 07, 2022 08:24

  I have not enabled I2S on my Pi. So the setup works for me with SPDIF input and Pi connected.

• 0
  
  HiFiBerry team January 07, 2022 08:29

  Ok, as long as you don't use audio on the Pi, this will work fine.