After the high-luminosity upgrade of the LHC, the electromagnetic calorimeter and the hadron calorimeter of CMS Barrel must cope with an increase in the number of interactions per bunch crossing and an increase in radiation levels. CMS implements a sophisticated two-level triggering system composed of the Level-1, instrumented by custom-designed hardware boards, and a software High-Level-Trigger. To this end, the off-detector electronics have been redesigned with increased capabilities, exploiting increased granularity of both calorimeters at Level-1. The paper focuses on this new off-detector electronic board design.