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Slow Heart rate unable to read

Joy Tan
Expert 1175 points
Other Parts Discussed in Thread: MSP430FG439

Hello,

I am doing project for Sport watch on heart rate monitoring using MSP430FG439.

I am using the source code from MSP430FG439, C source files ("Heart rate.c", "Heart rate with DAC output.c", and "Heart rate with EKG Demo.c")

I tested the code and design. It is able to work correct when measuring heart rate of 80 to 90. But my design is unable to work when the heart rate is at the range of 40-50.

May I know this is due to the limitation for the source code? which area can I amend on the code? Or do you have other working source code?

Or is this due to the hardware limiation of MSP430FG439 chip? if so I am thinking to change to CC430 + extend Op amp.

Pls advise.

Thanks,

Joy

  • 0
    Expert 1175 points

    Dear all,

    Is there any one have any idea on this?

     

    Thanks,

    Joy

  • 0 in reply to Joy Tan
    Guru 227245 points

    Apparently not.

    If you're usign a TI demo code, you should consider that the code is "only intended to be used for the intended use". That means, it is for exactly the purpose described. It usually does not scale, cannot be moved easily to a different MSP than the one it was originally written to, oten uses programming tricks and implicite side-effects which are not covered in any comment.

    As you said, it works for 80-90 Hz, which is the normal rate for humans. It does not mean that it will work for slower or higher rates that the 'normal' (or whatever was considered 'normal' for the coder). Counters may overflow or generate a division by zero if you leeave the original range.

    The demo codes are just demonstration how this exact problem could be solved. They are not meant to be (or at least usually cannot be used as) base code for own experiments, unless you exactly know what they are doing (and if you finally do, you're better off with your own code then).

    Well, if you finally understand how the code works, you'll also be able to detect why it doesn't work for lower heart rates.

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