The Research Of The Interface Of Hydrological And Meteorological Data Acquisition Based On Open Bus

Marine hydrological and meteorological data acquisition systems usually containseveral sensors for multiple observation items. The current structure of system is that datalogger connected each sensor with a dedicated channel. It causes multiple problems suchas make connect the wire complex, make the system bad expansibility and so on. In orderto solve this problem, this article introduces open bus technology that applied tohydrometeorological data acquisition system, and designs SDI-12bus and NMEA2000bus interfaces after researching these buses communication protocol deeply. All thesesensors are communicated with data logger by these buses which simplify the structure ofthe system. In addition, SDI-12bus interface can be changed to other communicationprotocols such as RS-232, RS-485and RS-422controled by software which expand thefunction of the interface.This article introduces the method of realizing the bus interface from hardware andsoftware respectively. The hardware respect is designing hardware interface circuit ofSDI-12bus and NMEA2000bus in order to achieve physical layer signals transceiver.Chip selection and schematic design of each module are introduced. The software respectis realizing data link layer and the upper layer protocol of SDI-12bus and NMEA2000bus which contain receiving and transmitting frame, parsing packets and managing buses.The software development environment is Keil and RTX real-time operating system. Thispaper describes the operating system and multi-task design in this platform. The programis designed in module in order to be maintenanced easily in the future, each module has adetailed flow chart instructions.Finally, a number of hydrological and meteorological sensors are connected to theSDI-12bus and NMEA2000bus in order to verify the performance.The result shows that hydrological and meteorological data acquisition interfacebased on open bus can collect data correctly. It makes the data acquisition system havemany advantages such as good expansibility, simply hardware circuit, easy connectingthe wire, easy installation and so on.