Orb410:
Iset Imeas ADC
4    4.07  12335
12   12.20 37318 
20   20.35 60313

Irec = P0 + P1*ADC

4.07  = P0 + P1*12335
12.20 = P0 + P1*37318

12.20-4.07 = (37318-12335) * P1

P1 = (I1 - I2) / (ADC1 - ADC2)
P0 = I1 - P1*ADC1

P1 = (12.20 - 4.07) / (37318-12335) = 3.25421286474802810e-04
P0 = 4.07 -  3.25421286474802810e-04*12335 = 5.59284313333074934e-02