A methodology for the closed-loop automatic tuning of an event-based PI controller is proposed in this article. In particular, the technique consists of performing two relay feedback experiments with a symmetric send-on-delta (possibly roughly tuned) PI controller already in place. The evaluation of the process variable allows for the determination of the parameters of a first-order-plus-dead-time process transfer function that is eventually employed to tune the controller parameters. Simulation and experimental results demonstrate the effectiveness of the methodology.