I am using this board and this works:


Now, I wanted to integrate an SGTL5000 (the above board's CODEC) in a custom board. I designed it and I already have it with me, a local store made it for me and soddered the components.

I suppose the next step would be to just record as I do with the above board:

    sudo arecord -r 44100 -f S32_LE test.wav

and with the FE-PI 2 board it works ok, with mine I only record noise.

Doesn't the kernel driver take care of everything such as I2C configuration? I double checked the power voltages between the boards and it is relatively the same, give or take 50-100mV, and also the oscillator.

Basically the question is: when using a driver for an I2S CODEC, does the driver take care of the I2C configuration or does the chip need to be "flashed" one time first or whatever?

EDIT: Something is wrong, when I measure the MIC_BIAS voltage on the chip of the working board it gives 2.54V, and when measuring the same pin on my board it only gives 1.49V. I tried setting the voltage manually using a python program but the chip address appears to be locked by the driver. I'm now studying how drivers work so I can get a better understanding on what is happening.

EDIT2: Found the problem, the bias resistor and the cap that is between the MIC_BIAS pin and ground were switched in production, that was the problem. I have to learn how to silkscreen better on Eagle...

  • Boards which cover the GPIOs maybe exploiting the EEPROM ID pins (physically 27 & 28) to load a kernel driver via a device tree overlay.
    – goldilocks
    Dec 3 '17 at 21:07
  • This one doesn't. From the board's website: drive.google.com/file/d/0B6Iw7GrAjGT_NWdJV2VaM2NrUWs/view mine is basically a copy of the circuit with more stuff on the board for other systems. I'm only testing one at a time though... I don't expect ghostly EMF interference from other systems :(
    – rmarques
    Dec 3 '17 at 22:39

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