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DIGI2 PRO V2.2 + DSP clock circuit

Henry Pootel

January 21, 2024 00:22

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HiFiBerryOS 20230404, Digi2 Pro + DSP, Pi 4 Rev. 1.4 

In the GPIO usage documentation for the Digi2 Pro, it says that GPIOs 5 and 6 are used for the clock circuit and cannot be used for anything else.

GPIO usage of HiFiBerry boards | HiFiBerry

When I use sox to play a test tone, and probing with an oscilloscope, I see the I2S signals on GPIO18, 19, and 21, but do not see any waveform on GPIO5 (pi header pin 29) or GPIO6 (pi header pin 31).

Two questions:

Is this my failure in probing or should I expect no clock signal on these lines?

Does the pi send the optional I2S MCLK signal to the Digi2 Pro and/or the DSP?  (Do these HiFiBerry cards need it?  If so, on what pi header pins?)

Thanks!

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2 comments

• 0
  
  HiFiBerry team January 22, 2024 09:03

  > should I expect no clock signal on these lines?
  There is no clock signal on these. They are just use to select the correct clock signal
  
  >Does the pi send the optional I2S MCLK signal to the Digi2 Pro and/or the DSP? 
  No, the Pi does not send ANY clock signal as the clocks are generated from the Digi2 Pro.

   

   

• 0
  
  Henry Pootel January 23, 2024 08:18

  Excellent, thank you.  (LOL ... embarrassed that I missed that!)

             GPIO5    GPIO6
  44100      H        L
  48000      L         H
  88200      H        L
  96000      L         H
  192000    L         H

  Used to select the correct oscillator (of the two on the Digi2 Pro) for the current sample rate.

  Edited by Henry Pootel January 23, 2024 08:24