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PCM5122: I2S audio loop back with PCM1860 and PCM5122

Buli Xu
Intellectual 400 points
Part Number: PCM5122
Other Parts Discussed in Thread: PCM1860

I am trying to implement BT audio loop back test with the following schematic using PCM1860 and PCM5122.

PCM1860 is configured in hardwire mode with fs = 44.1kHz, I2s mode, channel#1 activated. PCM5122 is also configured in hardwire mode with clock signals (BCK and LRCK) in slave mode, I2S mode, etc. 

Once VINL1 and VINR1 of PCM1860 are supplied with 250Hz 1Vpp sinusoidal wave, I am expecting similar sinusoidal waves at OUTL and OUTR of PCm5122. But I got nothing on OUTL and OUTR. Attached please find captured DIN, BCK and WCK at PCM5122 input side. Measurements results: f_WCK = 44.1kHz and f_BCK=64*44.1kHz = 2.817MHz.

what am I missing?

Since PCM5122 has slave clock BCK and WCK as inputs. Does it still need a SCK clock?

Thanks,

  • 0
    TI__Guru 57800 points

    Hi, Buli,

    The schematics and configuration seems correct, also the I²S signals from the PCM1860 seems correct as DOUT is sending proper data to the PCM5122. This makes me think that the issue is in the PCM5122 side.  If the PCM5122 detects that SCK is tied to ground, the internal PLL will generate the required system clocks from stable BCK. Do you have the same behavior after providing a proper SCK signal to the DAC?.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Intellectual 400 points

    I tried to lift SCK pin on PCM5122 earlier and will try to ground SCK pin and report back results.

    BTW, sometimes BCK voltage swings below 1.8V (0 to 1V square wave) when it is first powered on. The problem gets fixed after a few times of power cycling. Have you seen this before? Any comments?

  • 0 in reply to Buli Xu
    Intellectual 400 points

    Ground SCK pin doesn't not help.