The ATLAS hadronic Tile Calorimeter (TileCal) will undergo major upgrades to the on- and off-detector electronics in preparation for the high luminosity program of the LHC in 2026, so that the system can cope with the HL-LHC increased radiation levels and out-of-time pileup. The on-detector electronics of the upgraded system will continuously digitize and transmit all photo-multiplier signals to the off-detector systems at a 40 MHz rate. The off-detector electronics will store the data data in pipeline buffers, produce digital hadronic tower sums for the Level-1 calorimeter trigger system, and read out selected events. The modular front-end electronics feature radiation-tolerant commercial off-the-shelf components and redundant design to mi...