The JEM-EUSO (Extreme Universe Space Observatory on-board the Japanese Experiment Module) international space mission is designed to observe UHECRs by detecting the UV fluorescence light emitted by the so-called Extensive Air Shower (EAS) which develop when UHECRs interact with the Earth's atmosphere. While this "fluorescence technique" is routinely used from the ground, by operating from space, JEM-EUSO will, for the first time, provide high-statistics on these events. In preparation for JEM-EUSO is a set of pathfinder experiments with a common set of electronics, consisting of one Photo-detection Modules (PDMs) identical to the 137 that will be present on the JEM-EUSO focal surface. In this presentation, I will describe each instrument, present the details of the design and the fabrication of the PDM and PDM control board, as well as the EUSO-TA and EUSO-Balloon integration tests. I will report on the EUSO-Balloon campaign and results, including a specific analysis developed to search for global variations of the ground UV emissivity, and apply a similar analysis to data collected at the site of Telescope Array. Finally, I will present the implementation and testing of the first-level trigger (L1) within the FPGA of the PDM control board.