Research On PCIe-Camera Link Image Signal Generator Based On FPGA

With the development of space technology,meteorological observation,geography mapping and other space tasks need to obtain high-resolution images through aerospace CCD camera.In order to ensure the normal operation of the on-board image acquisition and processing unit in the orbit,it needs to be adequately tested on the ground.Aerospace CCD camera is expensive and easily damaged,it also is difficult to flexibly output the test images with different resolution and specific content.Therefore,using aerospace CCD camera in the test of on-board image acquisition and processing unit is inappropriate.According to a on-board image acquisition and processing unit ground test equipment development requirements,this paper designed a image signal generator based on PCIe-Camera Link,and researched the key technologies such as high-speed data transmission and caching.The image signal generator received the image data from the host computer through PCIe,then output the image data in the Camera Link standard by data buffer,protocol conversion and level conversion.Firstly,according to the function and specification requirements of the image signal generator,the overall design scheme of the system was proposed.To reflect the modular,versatile and scalable design principles,hardware system design of image signal generator was divided into FPGA main control board,high-speed transmission interface board and Camera Link output board.FPGA main control board contained FPGA chip and DDR3 memory chips,high-speed transmission interface board contained PCIe,SFP port and other common transmission interfaces,Camera Link output board contained Camera Link driver chips and interfaces,the three independent boards were interconnected through high-speed connectors.Secondly,the FPGA program design of image signal generator was introduced.The FPGA program included the PCIe data receiving unit,the image data buffer unit and the Camera Link image output unit.The PCIe data receiving unit received the image data through the PCIe DMA,the image data buffer unit carried on the image data caching through DDR3 chips,Camera Link image output unit achieved the image to Camera Link format output.Finally,a design scheme was proposed for the overall test on image signal generator.The host computer software was designed.The PCIe data receiving unit,the image data buffer unit and the Camera Link image output unit was separately tested.Then,using the image acquisition board,this paper built a closed-loop test loop of "computer-image signal generator-image acquisition card-computer",and a whole test of image signal generator was carried out.The test results showed that,this design can totally realize the predetermined functions and meet the technical requirements.The image signal generator source could support a variety of resolution,arbitrary content of the image output,and flexible choice of different Camera Link configuration modes.This design used the whole FPGA implementation,and achieved high-resolution image real-time output.The design of this paper was applied to the ground test of a on-board image acquisition and processing unit,which could greatly enhance the flexibility,comprehensiveness and reliability of the test,improve the test efficiency,reduce the CCD camera damage risk and test cost.