Systems, methods and apparatus for configuring a fingerprint sensor to operate in a capacitive sensing mode and an ultrasonic sensing mode are disclosed. A fingerprint sensor may be configured to operate in a capacitive sensing mode by driving a sensing electrode using a controller. In some implementations, an object positioned on or near the sensing electrode may be detected using the fingerprint sensor in the capacitive sensing mode, and the controller can drive electrodes of the fingerprint sensor differently to configure the fingerprint sensor to operate in an ultrasonic sensing mode. In some implementations, an applications processor may be instructed to authenticate a fingerprint of the object from image data obtained when the fingerprint sensor is operating in the ultrasonic sensing mode. In some implementations, a display of a mobile device containing the fingerprint sensor may be unlocked, or the mobile device may be woken up when the fingerprint is authenticated.