Over-The-Air Programming (OTAP) technology was developed originally to enable device manufacturers and network operators to deliver updated firmware for mobile handset. The growing popularity and complexity of wireless sensor networks implies the importance of usage of such technology (OTAP) the same way it is used in mobile networks. The idea of this work is to enable firmware update of motes and sensor interfaces used in wireless sensor networks in their final locations from a central base station. This work also focuses on the development of PSoC based sensor interface board. The usage of PSoC in sensors interfaces allows for a broad range of sensors to be interfaced. Signal conditioning, filtering and amplification tasks are all preformed on the PSoC chip and can be modified and tuned by means of OTAP. A complete OTAP working flow is detailed to program the developed PSoC sensor interface board. The OTAP of this sensor board is implemented using a very low power CPLD device.