Methods and apparatuses for configuring an implantable device to interface with retina cells are described. The device may comprise an array of pixel units capable of stimulating the retina cells are described. The pixel units may operate in a mode of operation selected from a plurality of modes including a normal mode and a calibration mode. A control circuitry of the device may be configured to switch the mode of operation for the pixel units. In one embodiment, the pixel units may be configured to receive light for stimulating the retina cells during the normal mode to enable perception of the light. During the calibration mode, the pixel units may be configured to adjust amount of stimulation to the retina cells.