The High-Luminosity Large Hadron Collider will increase the sensitivity of the ATLAS experiment to rare physics processes. In order to cope with a 10 times higher instantaneous luminosity compared to the LHC, the trigger system of ATLAS needs to be upgraded. The ATLAS experiment plans to increase the maximum rate capability of the 1st trigger level to 1 MHz at 10 µs latency. This requires new on- and off-chamber electronics for its muon spectrometer. The planned upgrade of the on-chamber electronics for the ATLAS Muon Drift-Tube (MDT) chambers is de-
scribed in this proceedings.