In recent years wireless body area sensor networks (WBASN) has gained a lot of attention from researchers for its promising application in medical care and health care field. However, previous studies are typically involved in the deployment and performance of WBASN, and most research has barely considered the details of the hardware and software platforms. Furthermore, few existing platforms can meet the need of the practical application for their larger physical size, higher power consumption, etc. In this paper, a hardware-software platform (HSPF) is presented, which is especially designed for the application in WBASN. HSPF provides a “core” of the WBASN solution, which puts the most required hardware and software in a small package (24.8×19.0 mm). We discuss how the hardware components are selected to achieve the design goals: low power consumption and small size. Meanwhile, the current consumption of the hardware module of HSPF is evaluated. In addition, the architecture of the software module of HSPF and the design of the integrated star network transport (SNT) protocol are detailedly described. HSPF has been successfully used in our recent research project.