  At the end of the Large Hadron Collider's Run 2, CERN's Proton Injector Linac
2, commissioned in 1978, delivered its final beam in December 2018. For Run 3,
from March 2021, a new H$^{-}$ will take over the role: Linac4. The machine has
been producing test beams since 2013 and in 2016 it reached its design 160 MeV
energy with 20 mA beam current. Since then several improvements have been made
which enhance the LLRF performance and stability. In this paper the structure
of the machine and the control system are presented. Problems arising from
different RF station types are described and our solutions explained, along
with new features recently added to the LLRF. An Adaptive Feed Forward
implemented as a flexible hybrid hardware-software solution is described, and
first results of this application running on a laboratory test stand are
presented. Addition of the set point modulation needed for longitudinal
phase-space painting is discussed. Finally, software tools for automation of
setting up, monitoring and operations are described. As the hardware and
low-level software are still reaching maturity, these are only briefly
introduced here.
