Yoyo dynamics are discontinuous and highly nonlinear, and dynamic parameters are difficult to estimate precisely. Some parameters even change their sign at the loop bottom of yoyo’s trajectory. Humans predict parameter change timing visually and sense yoyo dynamics through the fingers. Designing a robot that plays with a yoyo is difficult due to a lack of sensors and dynamic equations for sensing yoyo movement. We propose eventbased formulation for this based on an energy balance model and event-driven control. Simulations and experiments verified the validity of formulation and controller design.