Incremental Encoder Position Interpolation

An article of manufacture comprising a non-transitory storage medium having instructions stored thereon that, if executed, result in:

• receiving a first signal from an incremental encoder;
• producing a coarse position of the incremental encoder and a lookup address based on the first signal;
• retrieving a lookup value representing an arcsine or an arccosine of a value of the lookup address from a lookup table;
• calculating a fine position of the incremental encoder using the lookup value;
• and
• providing an interpolated position of the incremental encoder based on both the coarse position and the fine position.

An apparatus to provide an interpolated position of an incremental encoder, the apparatus comprising:

• at least one input configured to receive first information related to a first signal and second information related to a second signal;
• a quadrature state machine coupled to the at least one input and configured to track a quadrature relationship of the first signal and the second signal, the quadrature state machine providing a quadrant output and counter control lines;
• a coarse position counter coupled to the counter control lines and configured to increment and decrement under control of the quadrature state machine;
• address calculation circuitry, coupled to the at least one input and the quadrant output of the quadrature state machine, and configured to generate a lookup address output;
• a memory having an address input coupled to the lookup address output and storing arcsine or arccosine values of corresponding lookup addresses;
• and
• circuitry to generate the interpolated position of the incremental encoder based on both an output of the coarse position counter and an output of the memory.