MSP430FR50431: Parabolic Interpolation for Absolute ToF Calculations

Boone

Part Number: MSP430FR50431

Hello,

I'm trying to analyze captured ADC data in order to best determine a ratio lobe to peak value in Matlab. How can I implement the parabolic interpolation in Matlab as described in section 2.2.1.1 of SLAA889? I've started with interp1() using the 'spline' method, but I suspect that's quite different from what the firmware actually does.

Thanks!

over 3 years ago

0 Leonardo Estevez over 3 years ago

TI__Genius 12615 points

Hi Boone,

I think you can reference some threads on how to do this from the Matlab forum:

https://www.mathworks.com/matlabcentral/answers/488351-how-to-make-a-parabolic-interpolation

BR,
Leo

+1 Boone over 3 years ago in reply to Leonardo Estevez

Prodigy 185 points

Hi Leonardo,

Thanks for the advice. I'm actually using Octave, not MATLAB, which is mostly the same but doesn't support cftool. I was able to use polyfit with a second order polynomial. I think that's the same thing as a parabolic interpolation, but please let me know if I'm mistaken.

Here's a snippet for how I accomplished finding the X and Y coordinates of the interpolation peak:

polyCoef = polyfit([-1 0 1],[rawADCData(sample_index-1) rawADCData(sample_index) postADCData(sample_index+1)],2);
r = roots(polyder(polyCoef));
lobeY = polyCoef(1)*r.^2 + polyCoef(2)*r + polyCoef(3);
lobeX = sample_index+r;

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MSP430FR50431: Parabolic Interpolation for Absolute ToF Calculations