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FDC2214EVM; the reason of red LED lighting

Takao Yamamoto
Genius 4135 points

Dear all,

Normally, green LED is lighting.

However red LED is lighting on my EVM.

Could you teach me the reason why?

I know this LED is the indicator of USB connection.

In my board, I only changed sensor configuration.

And connection is built.

Why red LED is lighting?

I can not believe the data from EVM because of red LED.

Best regards,

  • 0
    TI__Expert 8050 points
    Hello Yamamoto-san,

    The red LED simply indicates the sensor frequency is different from the default value, which is expected after you changed the sensor configuration.

    Regards,
    Yibo
  • 0 in reply to Yibo Yu
    Genius 4135 points

    Dear Yibo,

    Thank you for your reply.

    And I have understood the mean of LED lighting.

    In this opinion,

    is the answer of following post wrong?

    At following post, the LED indicate connection of USB...

    Best regards,

  • 0 in reply to Takao Yamamoto
    TI__Expert 8050 points
    Hello Yamamoto-san,

    It looks like the previous responder probably did not realize that the sensor had been modified. Thank you for the notice and I will add a comment to that thread.

    The red LED indicates that the FDC is not measuring the default frequency when it powers up. This can happen if there's some connection issue, or if the sensor had been modified.

    You can do a quick experiment to verify that. Plug in an unmodified EVM and you should see the green LED light up. Now unplug the EVM, hold the EVM sensor with your finger and plug it in again. You should see the red LED light up, because the capacitance due to your finger will cause the oscillation frequency to change.

    Regards,
    Yibo
  • 0 in reply to Yibo Yu
    Genius 4135 points
    Dear Yibo,

    Thank you for your reply.

    I could do your way and see the red LED light up!

    Best regards,