具備USB 2.0 UVC裝置之嵌入式影像擷取系統設計

在目前的居家保全與在行車影像紀錄器的應用上，即時影像顯示的需求越來越多。同時，各種可攜式的webcam影像擷取裝置亦陸續被開發與設計。但其中，webcam輸出介面是不統一或是需要另外設計的電路去連接到webcam元件上，因此，使得webcam在設計開發上極為不便利。隨著USB UVC(USB Video class)群組規範的提出，讓USB webcam的應用越來越廣泛。但是USB webcam相關的應用大多是以PC主機或是筆記型電腦為主。因此，本研究主要是以USB 2.0為架構，去設計一個USB UVC數位影像擷取裝置，以及將影像顯示在Android作業系統的嵌入式影像擷取系統上。其中，USB UVC數位影像擷取裝置是使用OV7670 COMS IC (OmniVision)，並結合Cyclone II FPGA開發板(Altera)。此外，USB UVC裝置則是採用EZ-USB FX2 USB 2.0晶片組(Cypress)以設計出一個符合UVC群組規範的USB 2.0裝置。FX2 USB 2.0晶片組可以控制SCCB匯流排以擷取到OV7670所感測到的數位影像資料。其中，OV7670的輸出影像格式為YUV422，可以方便使用者轉換與進一步做影像資料分析處理。而透過V4L2視訊驅動程式在嵌入式影像擷取系統後，即可連接所自行開發的USB UVC數位影像擷取裝置，並實現即時影像的擷取與顯示。本研究所開發的技術，未來可廣泛應用在各種可攜式平台的應用上。

關鍵字

USB ； UVC ； Embedded System ； Android ； webcam

並列摘要

The demand of real-time video display functions in home security and vehicle video recorder ‘applications are rising. A variety of portable webcam image capturing device has been developed and designed in succession. However, the webcam’ interface is not standardized or it still requires additional circuit design to connect to other webcam components. Therefore, it is inconvenient for develop and design. With USB UVC (USB Video Class) class specification is proposed, the USB webcam is applied more widely. Though most USB webcam-related applications are based on the PC host or notebook based, therefore, this study is mainly to design a USB UVC digital image capturing device based on USB 2.0 architecture. The digital image is displayed on the embedded image acquiring system with Android operating system. Meanwhile, the OV7670 COMS IC (OmniVision) and Cyclone II FPGA development board (Altera) are adopted and combined in the USB UVC digital image capturing device. The EZ-USB FX2 USB 2.0 chipset (Cypress) is utilized to design and meet with USB 2.0 devices of UVC specification. The EZ-USB FX2 USB 2.0 chipset can control the SCCB bus to retrieve the OV7670 sensed digital image data. The output image format from OV7670 is YUV422 and users can easily convert image data for further analysis and processing. The V4L video driver is porting in the embedded video capturing system to connect USB UVC digital image capturing device to achieve real-time image capture and display. The development of current study can be further widely used in the application of various portable platforms.