Driving sensor electrodes for absolute capacitive sensing

A method of driving sensor electrodes for capacitive sensing, comprising:

• driving the sensor electrodes with a capacitive sensing signal to measure first changes of capacitance between each of the sensor electrodes and at least one input object;
• driving at least one sensor electrode in a first set of the sensor electrodes with a reference signal and at least one sensor electrode in a second set of the sensor electrodes with a capacitive sensing signal to measure second changes of capacitance between the at least one sensor electrode in the second set and the at least one input object;
• and
• determining a capacitive image based at least in part on the first and second changes of capacitance.

An input device, comprising:

• sensor electrodes;
• and
• a processing system coupled to the sensor electrodes, the processing system configured to:
• drive the sensor electrodes with a capacitive sensing signal to measure first changes of capacitance between each of the sensor electrodes and at least one input object;
• drive at least one sensor electrode in a first set of the sensor electrodes with a reference signal and at least one sensor electrode in a second set of the sensor electrodes with a capacitive sensing signal to measure second changes of capacitance between the at least one sensor electrode in the second set and the at least one input object;
• and
• determine a capacitive image based at least in part on the first and second changes of capacitance.