The Lower Atmosphere/Ionosphere Coupling Experiment (LAICE) CubeSat mission includes the payload instruments that generate scientific data by interacting with the flight computer. The LAICE Instrument Interface Board (LIIB) is designed to interface with the payload instruments and the flight computer for efficient operation of the LAICE. The uplink command packet contains commands for regulating power supply to the payload instruments and for interfacing the peripheral, called the thermal knife, with the science instruments. The LIIB is responsible for interpreting these commands in order to execute the associated functions. The architecture of the LIIB is designed such that it not only takes into account all the requirements of the systems and instruments on the LAICE, but also ensures smooth flight data analysis at the ground station end. The approach taken to build the design makes the entire process intuitive and easier to debug. This thesis describes the design and development of the LIIB firmware, to ensure proper functioning of the LAICE. The firmware design is presented first, by initially defining the architecture based on the system requirements and progressing eventually to its development at the system level. End-to-end testing with the payload instruments and thermal knife setup verifies the operation of the LAICE LIIB firmware and electronics, thus qualifying the instrument for deployment within the LAICE.