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
    Commented Dec 3, 2017 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
    Commented Dec 3, 2017 at 22:39


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.