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Problem reading pulse values AFE4400 + SFH7050

-javier-
Prodigy 35 points
Other Parts Discussed in Thread: AFE4400, AFE4404, AFE4404EVM

Good morning.

I have my own board with afe4400 connected with a sfh7050 sensor to read pulse and oxigen. At this moment I use sensor with my finger and all works, the signal and values of my pulse are correct.

This is a graphic with all values that it reads on my finger:

The problem is when I read values on my wrist. The aplication can´t detect pulse correctly.

This are the register that I use.

escribir_registro(LED2STC, 6050);
escribir_registro(LED2ENDC, 7998);
escribir_registro(LED2LEDSTC, 6000);
escribir_registro(LED2LEDENDC, 7999);
escribir_registro(ALED2STC, 50);
escribir_registro(ALED2ENDC, 1998);
escribir_registro(LED1STC, 2050);
escribir_registro(LED1ENDC, 3998);
escribir_registro(LED1LEDSTC, 2000);
escribir_registro(LED1LEDENDC, 3999);
escribir_registro(ALED1STC, 4050);
escribir_registro(ALED1ENDC, 5998);
escribir_registro(LED2CONVST, 4);
escribir_registro(LED2CONVEND, 1999);
escribir_registro(ALED2CONVST, 2004);
escribir_registro(ALED2CONVEND, 3999);
escribir_registro(LED1CONVST, 4004);
escribir_registro(LED1CONVEND, 5999);
escribir_registro(ALED1CONVST, 6004);
escribir_registro(ALED1CONVEND, 7999);
escribir_registro(ADCRSTSTCT0, 0);
escribir_registro(ADCRSTENDCT0, 3);
escribir_registro(ADCRSTSTCT1, 2000);
escribir_registro(ADCRSTENDCT1, 2003);
escribir_registro(ADCRSTSTCT2, 4000);
escribir_registro(ADCRSTENDCT2, 4003);
escribir_registro(ADCRSTSTCT3, 6000);
escribir_registro(ADCRSTENDCT3, 6003);
escribir_registro(PRPCOUNT, 7999);

If someone could help me or say me one way to read correctly values on the wirst.

Thank you.

  • 0
    TI__Mastermind 49946 points
    Hello Javier,

    For reflective plethysmography especially on the wrist, the quality of PPG signal is dependent on, but not limited to, numerous factors like the mechanical design (Ambient light interference), the skin tone/pigmentation level, the hirsuteness of the test subject, the position of the arteries w.r.t to the sensor placement etc.

    Please follow the test setup guidelines mentioned in section 2.4 of the AFE4404 Users guide.

    The timing register settings look fine. Can you also ensure that the LED current and TIA gain settings are not too high that the TIA output is getting saturated?
  • 0 in reply to Praveen Aroul
    Prodigy 35 points
    Hello Praveen.

    I have seen users guide of AFE4404, section 2.4 and read all pdf, but the problem is that I haven´t board "AFE4404EVM", I see that board "AFE4404EVM" is more efficience and it is focus in heart rate and oxigen but at this moment, I use integrated "AFE4400" in custom board.

    I have read that green led is better to read heart rate and today I have changed the red led by a green led, now I can read heart rate in finger and in wrist but the problem is spo2 that I can´t read it (I receive data of oxigen about -120, 35 etc).

    I have read a lot of pages about spo2 and all pages using a red led. My question is If I can read reliable data of spo2 with the green led or I need a red led to do it.

    Thank you.
  • 0 in reply to -javier-
    TI__Mastermind 49946 points
    Hello Javier,

    The empirical data curves for peripheral oxygen saturation (SpO2) has been with red and IR LED.
    I am not aware of green LED being used for SpO2.
    Getting reliable Spo2 on the wrist has been a very tough nut to crack due to inherent issues that I had mentioned in my previous posts.
  • 0 in reply to Praveen Aroul
    Prodigy 35 points

    Thank for your answer.