close all
clear all

% curve fit for sharp gp2d12
% M Holden 4/05

% from data sheet
v = [2.4 1 .63 .5]; % volts
l = [10 30 50 80]/2.54; % inches

figure(1);plot(v,1./l);grid on;

invl = 1./l;

[P, S]= polyfit(v,invl, 1)

vfit = linspace(min(v),max(v),30);
invlfit = vfit*P(1) + P(2);
lfit = 1./invlfit;

figure(1);plot(l,v,'r+',lfit,vfit,'b-');grid on;

% convert to adc units:
slope = P(1)*5/1024;
offset = P(2);

fprintf('const float sensor_slope = %f; // (1/inch) per adc count\n', slope);
fprintf('const float sensor_offset = %f; // (1/inch)\n', offset);

figure(2);plot(l,v*1024/5,1./(vfit*1024/5*slope + offset), vfit*1024/5);