PPR = 1440 * 4   # decoder position steps per revolution


# update position state (absolute position mod 2**32) and determine relative position change
# input: new_position
# state: position
# output: position_delta
position_delta = ( new_position - position ) & 0xffffffff
position_delta |= -( position_delta & 0x80000000 )
position = new_position

# (option 1) convert relative position change to relative change in angle
# input: position_delta
# output: angle_delta
angle_delta = position_delta * 360 / PPR

# (option 2) use relative position change to track absolute angle
# input: position_delta
# state: position_mod_PPR
# output: angle
position_mod_PPR = ( position_mod_PPR + position_delta ) % PPR
angle = position_mod_PPR * 360 / PPR