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AFE4400: AFE4400

ahmad amini
Prodigy 50 points
Part Number: AFE4400

Hi, I am use AFE4400 in my pcb design to check and get SPO2 and Heart Rate with that.But I have problem with AFE4400 SPI. I can not get any data from SPI.It is not response to any read or write on register.Is there any body to help me?how can i solve it?here is my schematic, is it has any circuit design mistake?
thanks for attention...

  • 0
    TI__Mastermind 49176 points

    Hello Ahamd,

    Welcome to TI e2e forum!

    Please refer to #7 from the FAQ link: https://e2e.ti.com/support/data-converters/f/73/t/369445 to verify the AFE44xx sign of life after power-up.

    Ensure that RESETZ and AFE_PDNZ are logic high.

  • 0 in reply to Praveen Aroul
    Prodigy 50 points

    Hi. I do that factor mentioned in https://e2e.ti.com/support/data-converters/f/73/t/369445 and i can get like there but i cant get responce from register AFE4400 in spi communication:

    After ensuring the AFE power supplies are fine and setting RESETZ and AFE_PDNZ to logic high, you should measure the following:

    a) 0.75V on TX_REF pin (pin#9) for AFE4490.*

    b) 1V on BG pin (pin#7)

    c) 0.9V on VCM pin (pin#4)

    d) 4MHz clock on CLKOUT pin (pin#30) - assuming there is an external 8MHz crystal on XIN-XOUT pins.

    I send data as datasheet on spi but i can get answer from AFE4400.What I can do?

    Another question,what is SCLK bit rate exactly?because my micro controller can not work on sclk=8Mhz so i need a lower range.Can I set spi sclk on 250kbps ?

    Thanks for attention...

  • 0 in reply to ahmad amini
    TI__Mastermind 49176 points

    Hello Ahmad,

    SCLK can go up to 16MHz. You can set a lower range. 250KHz spi clk should be fine.

    Please check if your SPI timing waveform matches the ones shown in question # 8 in the FAQs. https://e2e.ti.com/support/data-converters/f/73/t/369445

    The host must be configured to latch serial data out on the falling edge so that AFE4400 can sample data in on the rising edge.  Likewise, the AFE4400 will shift data out on the falling edge so MCU can sample data in on the rising edge.

  • 0 in reply to Praveen Aroul
    Prodigy 50 points

    Here is my Altium designer file and psoc creater file. I checked data on MOSI that is fine but I dont know why AFE4400 does not responce.

    Please check my schematic and PCB and PSOC creator file and tell me where is mistake?Is there any power or another mistake?

    My micro controller is Cypress arm cortex M3 part number CY8C5468LTI_LP026

    Thanks for attention...SamaControl - SamaVital - V1.0.zipWorkspace01.zip

  • 0 in reply to Praveen Aroul
    Prodigy 50 points

    I make a signal as said in # 8 in the FAQs. https://e2e.ti.com/support/data-converters/f/73/t/369445

    all of signal is true but i do not know why AFE4400 does not naswer to me?How can i do to find the problem?

    first write to register 0->1 and second try to read regiter 0x30(here is problem I can not get answer from AFE4400. I checked data i oscilloscope to be sure my send data is true.

    at the first all i write RST and PDN pin's high.

    please guide me..

    it is very important for me...

    thanks for attention.

  • 0 in reply to ahmad amini
    TI__Mastermind 49176 points

    Hello Ahmad,

    Please share the voltages you are reading on the following pins: TX_REF, BG, VCM, CLKOUT, RESETZ, and AFE_PDNZ.

    In order to check the SPI write works, write 1 to register 23h (enabling software power-down by setting PDNAFE bit to 1), check BG / VCM voltage. You should read 0 V. Power up the AFE by writing 0 to register 23h. The BG / VCM voltages should ramp up.

    Once you have established SPI write works, you can check SPI read. 

    Pick a register for example register 2 and write a known value first and then read register 2 (after enabling SPI_READ bit).

    Share the oscilloscope SPI timing waveforms (all the SPI signals) of writing to register 2 and register 0 and reading from register 2.

  • 0 in reply to Praveen Aroul
    Prodigy 50 points

    Thanks a lot. Its solved and data read and write do correct.now I want to calculate SPO2 and Heart rate with AFE4400. I want to do that with micro controller Cypress PSOC5. Please guide me to do that and help me how can initialize AFE4400 to the best configuration and how can read SPO2 and Heart to calculate. I want to do that by C language.

    thank you for attention...

  • 0 in reply to ahmad amini
    TI__Mastermind 49176 points

    Hello Ahmad,

    Unfortunately, we do not support HRM and SpO2 algorithms. It is left open for the user to implement based on their requirements.

    However, one simple algorithm for heart rate can be counting the peaks in a given time frame to determine the heart rate.

    For SpO2 calculation, please refer to the app note for some guidance in the implementation.

    https://www.ti.com/lit/an/slaa655/slaa655.pdf

    There is no 1 best configuration to program the AFE with. I suggest that you use the AFE4400EVM's GUI to get the register settings for the AFE configuration. Using the GUI you can configure the timing registers just by entering required PRF and the LED ON time. Similarly, you can use the high-level controls of the GUI to configure AFE parameters such as TIA gain and LED current. Once you configure the AFE, you can save the register setting so then you can port it to your own MCU.