The Large Hadron Collider (LHC) at the CERN laboratory was designed to study the elementary particles and forces and search for new physics.  Detectors at LHC were designed to observe proton-proton collisions with center of mass energies up to 14 TeV, seven times higher than previously possible. One of the largest of these is the general purpose detector ATLAS. After almost 20 years of planning and construction, LHC and its detectors were finished in 2008. Since then ATLAS has produced valuable data, which contributed to the discovery of the 1964 postulated Higgs-particle and thus to the Nobel prize in physics in 2013. To expand the searches, LHC and its detectors will undergo several upgrades to the increase luminosity at least by a factor of 5 and to exploit the full potential of the machine. In order to adapt the detector to the resulting increasing event rates and radiation levels, new electronics have to be developed. This thesis describes the development process of a new upgraded digital readout system for one of the sub-detectors in ATLAS, the scintillating Tile Calorimeter (TileCal), and more specifically one of its key components, the high-speed data link DaughterBoard. Starting from the idea of transferring all recorded information of the detector using high speed serial optical links and the concept of using re-programmable logic for the readout electronics, completely new on-detector electronics were designed to be used as a core component for communication, control and monitoring. The electronics was tested, electrical characterized and proven to work in a setup similar to the upgraded readout electronics. The DaughterBoard is the Stockholm University contribution to the ATLAS upgrade in 2023.