  This work describes the architecture of a digital LLRF system for heavy-ion
acceleration developed under the specification of the projected future
heavy-ion accelerator facility in Huelva, Spain. A prototype LLRF test bench
operating at 80MHz in CW mode has been designed and built. The core LLRF
control has been digitally implemented on a PXIe chassis, including an FPGA for
digital signal processing and a real time controller. The test bench is
completed with a good quality signal generator used as master frequency
reference, an analog front end for reference modulation and signal
conditioning, small RF components completing the circuit, as well as a tunable
resonant cavity at 80 MHz, whose RF amplitude, phase and frequency are
real-time controlled and monitored. The presented LLRF system is mainly
digitally implemented using a PXIe platform provided by National Instruments,
and is based on IQ modulation and demodulation. The system can be configured to
use both direct sampling and undersampling techniques, resulting thus in a high
performance and versatile RF control system without the need of excessive
computational resources or very high speed acquisition hardware. All the system
is programmed using the LabVIEW environment, which makes much easier the
prototyping process and its reconfigurability.
