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AFE4403: Reading of LED2 changes little even with/wo removing finger

Edward Lee
Intellectual 1655 points
Part Number: AFE4403


Hi Team,

    My customer is designing AFE4403 in their board. They are developing the control scheme in the system now.

    First, they try to verify the hardware with our EVM.

    They break the communications interface between AFE4403 and their SOC. Then, connect the SPI of AFE4403 to our EVM and capture waveforms through the GUI.

    All functions work well and it could detect the change of the finger.

     Second, they remove the connections from our EVM and reconnect it to their SOC. 

     The soc only read the LED2 value(LED2VAL) but found the reading changes little.

      They had checked the ADC_RDY asserts periodically. 

      What other commands should they execute before reading the converted value?

     

It's kind of you to advise.

Thanks

Sincerely,

Edward 

  • 0
    TI__Mastermind 49986 points

    Hello Edward,

    Can you please check with the customer and confirm if the register readback works fine after enabling the SPI_READ bit?

    Also, another reason why one would see a fixed value is when the signal chain is saturated.

    Please share raw data and the AFE configuration for further debug.

  • 0 in reply to Praveen Aroul
    TI__Intellectual 1655 points

    Hi Praveen,

       Thanks for your feedback.

        Yes, the customer could read out all the registers after enabling the SPI_READ bit. 

        The communication should be OK.

        Also, I had checked the bias voltage at photo diode and found it's close to 0V. 

        That is the main reason causing the reading to be a small value.

        After solving the bias voltage issue, the converted value is back to normal.

    Thanks for your help.

    Sincerely,

    Edward