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Connecting different microcontroller to AFE4490 on AFE44x0SPO2EVM

Mohammad Hosseini1
Intellectual 610 points
Other Parts Discussed in Thread: AFE4490

Dear All,

As you've likely seen from my posts on this forum I have been in the process of building a reflective pulse oximeter using the AFE4490 and a the DCM03 sensor.


Until now I used the AFE4490 which I hand-soldered on a 40-pin QFN breakout board, and then placed that on a breadboard, which I then wired to my Arduino development board's SPI interface.


However, I'm having a hard time debugging my project when it comes to figuring out what is a hardware problem and what is a software problem, since hand-soldering and breadboards could be causing problems.

My new approach is to use the AFE44x0SPO2EVM and connect the AFE4490 on that board to my Arduino board's SPI interface. This means I want to disable/bypass the MSP430 on the EVM. I want the AFE4490 on the EVM to only communicate with my Arduino for reading and writing to the registers, etc.

What is the easiest way of connecting the AFE4490 on the EVM to my Arduino development board?


Thanks!

  • 0
    TI__Mastermind 49176 points

    Hello Mohammad,

    The only way of connecting AFE4490 on the AFE44x0SPO2EVM to your Arduino dev brd is to remove the series resistors on the digital interface and blue wire from the solder pad of the resistors closer to the AFE to the Arduino brd.

    Below are the list of the resistors to remove.

    Signal Series Resistor to remove Comment
    AFE_RESETZ R25 host (MCU) may drive logic high
    ADC_RDY R26
    STE R29
    SIMO R31
    SOMI R33
    SCLK R35
    PD_ALM R37 Optional
    LED_ALM R39 Optional
    DIAG_END R38 Optional
    AFE_PDNZ R42 host (MCU) must drive logic high

    In addition to these signals, connect GND between the two boards.

    Best regards.

  • 0 in reply to Praveen Aroul
    Intellectual 610 points

    Hi Praveen,

    Ok that makes sense. That's what I was planning on doing. Do I then need to add my own 10 ohm resistors between the EVM and the Arduino board? Btw, what do you mean by blue wire?

    In my current code, I'm not even using the ADC_RDY pin. I'm only using the 4 SPI pins. Is it necessary to utilize that pin?

    Also, I have the AFE_RESETZ and AFE_PDNZ connected to pull-up resistors

    Finally, I'm not sure what you mean by connecting the ground (GND) between the two boards. Are you saying to connect one of the GND points on the EVM to my boards GND pin? I'm using the board below.

    http://arduino.cc/en/Main/ArduinoBoardPro

  • 0 in reply to Mohammad Hosseini1
    TI__Mastermind 49176 points

    Blue wire refers to soldering wires on PCBs for patch work.

    I would suggest using ADC_RDY connecting it to an interruptible GPIO of host MCU. ADC_RDY can be used to interrupt the MCU to fetch the AFE data.

    Yes you will need to connect the GND on the AFE4490EVM to the Arduino Board GND.

  • 0 in reply to Praveen Aroul
    Prodigy 100 points
    Hi,

    I am trying to interface AFE4400evm to Arduino Uno. I interfaced R29, R31, R33, R35 to Arduino and I connected AFE_PDNZ to 3.3V using a pull up resistor. I don't see LED in finger sensor powered. Can you please help me out with this?

    Regards
    Likhitha
  • 0 in reply to Likhitha Neelisetty
    TI__Mastermind 18275 points
    There are a number of things that could be wrong. I would suggest looking at other posts of people who were successful using arduino.

    Have you checked the SPI signals to make sure you are getting the correct communication?