A low cost and flexible open source communications framework for temporally aligned sampling in distributed sensing systems

The ability to understand phenomena in environmental systems is reliant on the ability to measure data about the system. In this realm, a high degree of non-homogeneity can exist between adjacent measurement points. The barrier to increased spatial sampling is device cost. Newer low-cost sampling platforms enable increased spatial sampling allowing for a better understanding of phenomena. Many sensing applications also require temporal synchronization across distributed devices to understand phenomena. This work presents a novel, low cost and flexible communications framework built on open source technologies with a sample application. It allows for multiple devices to be connected via a bus topology and controlled and addressed from a single master device. A time synchronization strategy is presented that allows for low cost devices to be used for temporally aligned sampling without the need for complex and expensive time synchronization equipment. The wired system is based on the proven and robust RS-485 physical layer, and addresses numerous issues that are often encountered with other technologies. The sample application of low range differential pressure measurements demonstrates the functionality of both hardware and software components. This paper describes the design and implementation of the communications framework that can be used to measure distributed sensors with low cost, temporal alignment of data. The communications framework is available at https://github.com/sensingFramework.