Multi-frequency zero-row-sum code-division-multiplexing (CDM) touch sensing

An input device, comprising:

• a plurality of sensor electrodes, including transmitter electrodes and receiver electrodes;
• and
• a processing system configured to:
• drive the transmitter electrodes using multiple frequencies and multiple zero-row-sum code-division-multiplexing (CDM) drive matrices, wherein respective subsets of the transmitter electrodes are driven with sensing signals at respective frequencies of the multiple frequencies, and wherein each of the zero-row-sum CDM drive matrices corresponds to a respective frequency of the multiple frequencies;
• obtain resulting signals via the receiver electrodes based on the transmitter electrodes being driven with the zero-row-sum CDM drive matrices;
• decode the resulting signals;
• and
• determine presence, location and/or motion of one or more input objects based on the decoded resulting signals;
• wherein each zero-row-sum CDM drive matrix has a/b rows, where a is the number of electrodes of the transmitter electrodes, and b is the number of frequencies of the multiple frequencies.

An input device, comprising:

• a plurality of sensor electrodes, including transmitter electrodes and receiver electrodes;
• and
• a processing system configured to:
• drive the transmitter electrodes using a code-division-multiplexing (CDM) drive matrix;
• obtain resulting signals via the receiver electrodes based on the transmitter electrodes being driven with the zero-row-sum CDM drive matrix;
• decode the resulting signals, wherein decoding the resulting signals includes performing a signal level recovery process;
• and
• determine presence, location and/or motion of one or more input objects based on the decoded resulting signals;
• wherein performing the signal level recovery process comprises:
• for each respective receiver electrode, adding a signal level recovery value to each of a plurality of readings corresponding to the respective receiver electrode;
• and
• wherein the signal level recovery value corresponds to a value less than a median value of a set of readings corresponding to the respective receiver electrode.