Embodiments are disclosed that relate to touch input detection in a touch sensor. One example provides a method comprising establishing a first reference sequence, starting with a first set of candidate reference sequences each differing from the first reference sequence, reducing the first set of candidate reference sequences by applying a rule set to the first set to derive a relatively smaller second set of candidate reference sequences, for each candidate reference sequence in the second set of candidate reference sequences, calculating a touch detection performance score of a combined reference sequence, and configuring at least a portion of a receive circuit to correlate signals to at least one of the touch detection conditions by using the first reference sequence in a combined correlation operation with at least a selected candidate reference sequence from the second set of candidate reference sequences.