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4DPi-24-HAT -- I2S problem

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  • 4DPi-24-HAT -- I2S problem

    I'm building a project with 4DPi-24-HAT and MAX98357-based I2S DAC board from Adafruit.

    I managed to make the display working on Raspberry Pi OS 2020-08-20 build and a 5.4.68_4DPi+ kernel.

    I also managed to get sound out of the DAC.

    However, I have troubles making them both to work together. When I connect both, the DAC does not work. I get negative 5 Volts on the output of the DAC, and when I run
    I get a very loud noise ( even at 1% volume in alsamixer ) and on the second attempt I get a bunch of
    Write error: -32,Broken pipe

    All the problems go away if I power off my Raspberry, disconnect the display and power it back on.

    What I have tried so far:

    1. I checked that I have sufficient power to run both the display and the DAC using an in-line usb current meter.
    2. I tried soldering only power, SPI and I2C ID EEPROM pins between the display and the Raspberry. Display works, DAC has the same bad behaviour. So it looks like nothing to do with display interfering with the DAC pins ( also according to the datasheet it should not ).

    Anyone has any suggestions ? Can it be somewhere at the software side ?

    See some more info at the Adafruit forum.
    Last edited by susceptible; 25 January 2021, 03:03 AM.