Calibration of smartphone light sensors with a near field communication enabled reference

This paper describes a technique for calibrating the internal ambient light sensor (ALS) in smart phones. The calibration process depends on Near-Field Communication (NFC). The system consists of an NFC core implemented in an Field-Programmable Gate-Array (FPGA) development platform featuring the NFC analog front end circuit. In the proposed system, the smart phone interacts directly with a reference ALS through the NFC device The direct communication is possible with the help of a custom NFC command that controls an Inter-Integrated Circuit (I2C) master core in the FPGA. After the calibration process of the ALS in a smart phone is completed, the accuracy of the measurement is greatly improved. This is helpful to obtain precise information on the light intensity in indoor surroundings.