To achieve the swift development of heterogeneous designs, designers reuse existing hardware components to reconfigure their systems. However, current hardware design languages either require tremendous efforts to customize designs or sacrifice quality for simplicity. In this paper, we introduce SimpleChisel—a new Chisel extension that provides high-level semantics to efficiently generate heterogeneous designs. SimpleChisel standardizes the interface for better reusability and supports control-free specification with flexible data type conversion, which saves designers from the busy-work of interconnecting modules. Our results show that SimpleChisel considerably improves reusability and reduces design complexity for heterogeneous designs while maintaining high design quality.