The RFSoC-based electronics readout system for the BULLKID-DM experiment: sub-GeV dark matter detection with MKIDs

We present the readout and data acquisition (DAQ) system for BULLKID-DM, a cryogenic dark-matter experiment employing Kinetic Inductance Detectors (KIDs) to probe below 1 GeV dark matter candidates. The system is built around an AMD RFSoC (ZCU216) platform that synthesizes densely spaced probe tones, performs frequency demultiplexing and amplitude demodulation, and executes real-time triggering and background suppression across up to 16 readout lines with 145 resonators per line in the 700 MHz to 950 MHz band. A fully automated calibration flow integrates vector-network-analyzer (VNA) functionality, resonator-circle acquisition with in-firmware phase rotation for maximum trigger sensitivity, and an energy calibration scheme based on LED illumination via a mezzanine board on the FMC+ connector. We summarize architecture, firmware, preliminary phase-noise studies, and the status of the detector demonstrator. The system is ready for scale-up to the full BULLKID-DM detector at the Laboratori Nazionali del Gran Sasso (LNGS).