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AFE4490SPO2EVM: Reading registers from python code

Zakie Assad
Prodigy 40 points
Part Number: AFE4490SPO2EVM
Other Parts Discussed in Thread: AFE4490

Hello,

I am currently working on acquiring the PPG (Photoplethysmogram) signal using Python code. Initially, I attempted to achieve this by setting a sampling frequency using timers from Python libraries. In the timer's callback function, I read the LED data registers. However, I encountered issues with precision, as these timers did not provide the necessary accuracy for maintaining a stable sampling frequency.

Subsequently, I decided to read the data registers as quickly as possible to match the board's Pulse Repetition Frequency (PRF) of 500 Hz and ensure a known and stable sampling frequency. I managed to do this successfully in a simpler standalone code. However, I'm facing difficulties when integrating this continuous reading approach into my user interface, where I also need to plot the acquired signal.

My main question is whether there is a way to configure the board to operate in a continuous reading mode, sending data continuously to my PC, rather than periodically reading one value at a time. This would greatly help me in achieving my desired data acquisition setup.

  • 0
    TI__Mastermind 19815 points

    Hi,

    what do you mean by timer and timer's accuracy? Could you explain a bit more?

    when you say "my user interface", are you referring to the host/master or GUI you developed?

    --------------------------------------------------------------------

    Are you still using TI's EVM + MCU on EVM + EVM's GUI?  Or what might be your setup/topology?

    --------------------------------------------------

    What do you mean by " operate in a continuous reading mode"?

    For a host/master to read AFE4490's data registers, the master/host needs to detect&read the ADC_RDY and then read the corresponding value registers 42(2Ah) to 47(2Fh).

    Please refer to the datasheet instructions for these value registers -

    "At the rising edge of the ADC_RDY signal, the contents of all six result registers can be read out"

    "This register contains the digital value of the latest LED sample converted by the ADC.

    The ADC_RDY signal goes high each time that the contents of this register are updated.

    The host processor must readout this register before the next sample is converted by the AFE."

    Thanks

  • 0 in reply to ChienChun Yang
    TI__Mastermind 19815 points

    Hi,

    Since I haven't heard back from you,

    I am closing the ticket.

    Thanks