A microgrid (MG) is a cyber-physical system with coupled power and communication networks. The centralized secondary control of MGs with periodical communications restricts system efficiency and resilience. This article proposes a distributed event-triggered secondary control scheme in islanded MGs with its cyber-physical implementation. The proposed control scheme operates with the reduced frequency of communications depending on the MG states change "events" (e.g., load variations and communication failures). Besides, the secondary control objectives, including frequency/voltage regulation and accurate real/reactive power sharing, are decoupled into two timescales. Instead of designing event-triggering conditions (ETCs) for each secondary control functions, only ETCs for power sharing control in slower timescale are designed. Thus, the communication burden is significantly reduced since communications among neighbor controllers are only needed at the event-triggered time. The proposed controller has been tested on a hardware-in-the-loop (HIL) platform, where the physical system is modeled in the OPAL-RT and the cyber system is realized in Raspberry Pis. The control effectiveness is validated by the HIL results.