Serial Transmission Based on Pulse Width: Application to Water Bodies Monitoring

In this paper, a novel communications protocol, based on pulse width is presented, which is able to transmit data frames with bytes encoded in ASCII using a single transmission line. It is possible to transmit data between different embedded systems in the same electronic board or in different electronic boards. The computational cost is low and permits to transmit information in lengths up to 30 m. The protocol was tested in a system for measuring physichochemical parameters of water, composed of a floating body, a submerged probe to measure variables at different depths and a graphical user interface to receive and save data in a server. The floating body and the submerged probe are two independent embedded systems, interconnected with the proposed protocol; the system was implemented in a small water body, to cope with a relevant environment. The results show a good performance of the protocol in the transmission of data frames with high robustness, since in a period of 37 h the data were transmitted and received regularly, with a sample time of 5 minutes. The complexity of the algorithm was compared with other well-known protocols, resulting in fewer machine cycles, implemented in an eight-bit microcontroller.