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Original question:

PCM5242: No output in hardware mode

PCM5242: No output in Hardware mode

Aayush Aneja
Prodigy 20 points
Part Number: PCM5242

Hi Team, I am looking for a solution to my problem here with DAC-board using PCM5242 DAC. I don't get any audio output in hardware mode. The schematics and scope outs have been added here for your reference. It would be greatly appreciated if you could please provide me with some troubleshooting options in this regard.

Thanks,

Aayush Aneja

Schematic and scope_outs.pdf

  • 0
    TI__Guru 52683 points

    Hi Aayush,

    Are you applying 1.8v externally? As DVDD is connected to 3.3 volts, the LDOO pin will be internally driven and XSMT should be connected to 3.3V. 

    Is SCK coming from the same source as LRCK/BCK?

  • 0 in reply to Paul_Frost
    Prodigy 20 points

    I am not applying 1.8V externally. I will connect XSMT to 3.3V.

    SCK is coming from XT1 (24.576 MHz clock oscillator) on the PCB.

  • 0 in reply to Aayush Aneja
    TI__Guru 52683 points

    Is the SCK input clock also the reference clock for the LRCK and BCK? If not, it is likely causing synchronization issues.

  • 0 in reply to Paul_Frost
    Prodigy 20 points

    Hi Paul, In one of the previous posts, you mentioned that SCK should match table 32 in hardware mode using 4-wire I2S. The SCK is 24.576MHz, which matches table 32. So, I think it is reference clock for LRCK and BCK. I have attached the schematics and oscilloscope outputs with the original question. Please let me know if there is any issue with that.

    I am getting LRCK, BCK and DIN from Raspberry Pi. 

    Do you suggest that I should try 3-wire I2S to check if it works, if there is a sync issue?

  • 0 in reply to Aayush Aneja
    TI__Mastermind 25503 points

    Hi Aayush,

    Today is a holiday in the US. If possible you can try using 3-wire I2S and let us know your results. We will take a look when our team returns tomorrow or Wednesday. 

    Thank you,

    Katlynne Jones

  • 0 in reply to Aayush Aneja
    TI__Guru 52683 points

    Hi Aayush,

    To clarify, you have LRCK/BCK/DIN from the Raspberry Pi, but your SCK input is coming from some onboard oscillator? Is the SCK routed from the RPI as well? If not, they are likely not synchronized.  I recommend that you ground the SCK input and try operating in 3-wire mode.

  • 0 in reply to Paul_Frost
    Prodigy 20 points

    Hi Paul, No it's not routed to RPI.

    I tried the 3-wire too, it doesn't work either.

    To double check, I have cut tracks on the HiFiberry board (commercially avaliable) that uses PCM5242 to make it hardwired. This one works, when I configure it to hardware mode. But my custom designed board doesn't. Is it because I have not separated DVDD and AVDD?

  • 0 in reply to Aayush Aneja
    Prodigy 20 points

    Hi Paul, I checked with multimeter, the voltage reading at pin 9 is -1.5V, which I think is the problem. It should be -3.3V. Do you have any suggestions to fix this?

  • +1 in reply to Aayush Aneja
    TI__Guru 52683 points

    A few things you should check: You should add a 100nF capacitor on the LDOO pin to ensure that your 1.8V is valid.  You should also connect XSMT to 3.3V, not 1.8V.  Your SCK input is asynchronous to the LRCK/BCK, which will result in clock errors.  I recommend that you remove SCK and use the device in 3-wire mode.

    You should confirm that BCK is continuous and regular (the device does not support a gated BCK in 3-wire mode).

    Thanks,

    Paul