Convert dual pot "360 endless pot" to angle position

dual_pot_angle.py

# convert a dual pot "360 endless pot" aka sin/cos pot to angle position
# 17 Jun 2023
# JP found these cool dual pots that act like endless rotary encoders, 
#  in a Elektron Samples box.  They have two pots on a single shaft, 
#  one 90º out of phase. e.g. 
# RV112FF-40-15A-0B20K - http://www.taiwanalpha.com/downloads?target=products&id=79
#
# see: https://forum.pjrc.com/threads/59830-Read-Endless-Potentiometer
# answer: float angle = atan2f(potA, potB)
#

import time

# make up some fake "pot value" arrays that hold possible A & B pot values, 0.0-1.0
divs = 50
# A has an up ramp going from 0-180 degrees
a = [ (i/divs) for i in range(0,divs)]
# A then has down ramp from 180-360 degrees
a += [ 1-(i/divs) for i in range(0,divs)]
# B is 90 degrees phase offset from A
b = a[divs//2:] + a[0:divs//2]

# print out our arrays to show we match the datasheet
#print("a:", len(a), ["%.2f" % x for x in a], "\n")
#print("b:",len(b),  ["%.2f" % x for x in b], "\n")

while True:
    for i in range(0,divs*2):
        aval = a[i]
        bval = b[i]

        # convert knob positions aval & bval to angle
        if aval < 0.5:
            angle  = 360 - bval * 180  # here we show degrees to be clear
        else:
            angle  = bval * 180

        # angle = 360 - bval * 180 if aval<0.5 else bval *180

        print( "(%.2f, %.2f, %.2f)" % (aval, bval, angle/360))

Relevant datasheet section:

Output from Mu (with divs=50 so Mu x-axis scaling works better for us, orange is angle output -1-1)

(This is for the math.atan2() version. below for the simple linear solution graph)

Simple linear version (orange is angle output 0-1):