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AFE4404: AFE4404 in two LED mode

Samuel Conti
Intellectual 510 points
Part Number: AFE4404

Hello,

Actually, I use the AFE4404 in one LED mode to read heartrate at wrist, so with a green LED only. I use the supplied library and all is good.

I  want to read SPO2, so I will have a sensor with green/IR and red LED.

My first question is about the supplied library of the AFE4404, for SPO2 I will use 2 LED. I have the feeling that the library is designed for calibrate one LED, is it true ? (because I see the variable LED_Sel selects only one LED and all the code is a "if"..."else if" check on the variable).

how can I use the library for 2 LED calibration ? I see there is the initialize calibration anda periodic calibration, do I need to call them 2 times ?

- Initialize calibration is "OFFSET_DAC_Code_Est()" function, need to call it 2 times ?

- Periodic calibration is "CalibrateAFE4404()" function, need to call it 2 times too ?

Second question is about SPO2 LED, I need to take it at wrist, can I use the green LED ? or red LED is mandatory ? no problem with IR LED at wrist ?

Best Regards,

Sam,

  • 0
    TI__Mastermind 49956 points
    Hello Sam,

    We have received your inquiry about the device AFE4404 and will get back to you shortly.
  • 0 in reply to Praveen Aroul
    TI__Genius 12575 points
    Hi Sam,

    Yes, the provided library supports only one LED Phase.
    Calling some functions twice will not help you calibrate two LED phases.
    You have to modify the library at multiple places to support two LED phases.
    I would suggest, you can go through the calibration state machine and wherever the LED phase is calibrated , you have to modify to calibrate two LED phase.
    You can find the document for state machine at:
    C:\AFE4404EVMFWSRC-v1.4\AFE4404EVM_FW_SRC-1.4_release\Documents\AFE4404_Calibration_Conceptual Visualization.pdf.

    Regarding the LEDs for Spo2, the basic idea is to choose two LEDs that get absorbed differently by hemoglobin in the blood.
    And this difference in absorption is used to calculate the Spo2 levels.
    As we are not expert in this field, we can really comment about the Green LED, however mostly RED and IR are used .

    Regards,
    Prabin
  • 0 in reply to Prabin Yadav
    Intellectual 510 points

    Hello,

    Thank you for the feedback.

    Sam,