Design And Research On Reprogramming In WSN Nodes Based On Contiki

Ever since the concept of wireless sensor network has been proposed, variety of field has been developed such as MAC protocol, router protocol, power management, networking. And the technology has been applied in industry field monitoring, auto meter reading, intelligent building, smart house. Different from the nodes that in design stage, once the nodes is distributed into the actual application scenarios, the require will be changed by either the environment or man-made factor, while the replacement of device is difficult and costly. Thus the lifetime of software is shorted either. Research on reprogramming in distributed nodes has been more and more important.With the development of embedded system’s developing method, the great attention has been given to WSN OS. Firstly, various kinds of WSN operate systems, serial reprogramming methods and wireless code distributing method is analysised and compared in this thesis. An event-driven OS named Contiki is the main research object, the prototype of its protothread thread is analysised in this thesis. Apart from that, we introduce the other libraries in Contiki OS including Rime communicating protocol, tiny file system Coffee baesd on flash memory, and simple TCP/IP protocol uIP that can be distributed in 8-bit MCU.Secondary, two kind of reprogramming methods have been designed baesd on specific hardware. One is the enrire reprogramming, which is similar to LAP reprogramming. This method can replace the old binary files in rom aera with binary files that is produced by building tools entirely. Another is dynamic loading reprogramming, which parses, loading and run the relocatable target module with ELF loader tools in Contiki. Solutions have been implemented in K64F platform in above two ways, and software frame is designed and tested. By comparing the fractionation and depth of two reprogramming method, the second method is the better choice to be used in practical situations. Besides, the thesis considers security of file transporting and data integrity in reprogramming, which improves the fault tolerance of image updating.And at last the thesis conclude some problems and shortage in the implemention. The dynamic loading now can’t be ported to the CPU that don’t support ELF files, this will be the next research subject.