A Plug-and-play Approach Based on the I2C Standard

Plug-and-play architectures can reduce the timeline for constructing complex systems by automating the connections between components. While plug-and-play technologies have been successfully applied to aerospace systems, the overhead of the interface circuitry is a concern affecting its widespread use, particularly in smaller satellites. In this paper, we discuss a “minimalist” plug-and-play interface based on the popular inter-integrated circuit (I2C) standard, leading to dramatic simplifications of the interface circuitry necessary to be plug-and-play compliant. This concept, referred to as “mini-plug-and-play” (the space-qualified version is called “SPA-1”), has been created as a direct product of an international cooperative program between the United States and Sweden. At the simplest level, mini-PnP/SPA-1 is a protocol layer over I2C, readily implemented with existing devices that already support this ubiquitous standard. Using gateways, networks of mini-PnP/SPA-1 devices can connect to legacy forms of plugand-play (e.g., SPA-U and SPA-S). Like these other legacy interfaces, SPA-1 devices support key features of plugand-play, including electronic datasheets, automatic enumeration, and are readily integrated into plug-and-play software. This paper describes the development and demonstration of COTS and rad-tolerant versions of SPA-1 interface modules along with current status of the international program.