Research On Efficient Adaptive System Based On Direct Bitstream Evolution

Adaptive systems based on Evolvable Hardware(EHW)can adapt to the external environment by changing their structure and parameters,thus providing a good solution for electronics in aerospace.In view of the problems in mainstream EHW design methods caused by the coarse evolution granularity and the inability to generate bitstreams online(such as excessive system size,cost,resources,time and power consumption,as well as limited adaptability),in this paper,the idea of parsing and modeling the relationships between FPGA's resource and its configuration bitstream,and then generating the bitstream online based-on the models built,has been proposed.Thereafter,the framework and design scheme of the efficient adaptive system based on direct bitstream evolution are given.Finally,the proposed system architecture and design method have been verified by taking a 2-bit multiplier and an adaptive image filter as examples.And in these two cases,gate-level evolution and function-level evolution methods are utilized respectively.The main research contents of this paper are as follows:(1)The related works in EHW research has been introduced.And the the disadvantages of existing reconfiguration methods,evolution granularity,as well as bitstream parsing methods are analyzed.In view of these problems,the design method of evolution by modifying the bitstream file directly online has been proposed.Then the software and hardware paltforms needed are introduced briefly,and the information of FPGA resources and its configuration bitstream has been analyzed.(2)The method to parse the relationships between FPGA's resource and its configuration bitstream is given,and the configuration information of bitstream file has been analyzed systematically,and then the mapping relationships have been modeled.The corresponding online bitstream generation algorithms have also been designed for routing resources,logical resources,and the error correction code.Thereafter,the framework and design scheme of the adaptive system based on direct bitstream evolution is proposed,in which the chromosome coding approach of Cartesian genetic programming has been adopted,Block RAM is designed to cache the bitstream,and the bitstream file is directly modified by the models built.By this way,arbitrary evolution of logic functions and routing connections can be implemented.(3)Taking the 2bit multiplier as an example,an adaptive system based on direct bitstream evolution is built on the ML507 development board to verify the gate-level evolution method.The designs method of system software and hardware is given.The performance of the system is evaluated and analyzed.And the advantages of the proposed method over traditional methods is analyzed.Taking image filtering as an example,an online evolution system is built on the ML507 development board,to verify the function-level evolution method.The design methods of system hardware and software,and the filtering effects as well,are given.The experimental results show that the proposed method has lower resource cost,less storage space cost and higher evolution speed.It is not only suitable for the design of logic circuits using gate-level evolution,but also for complex circuits' s design using function-level evolution.