[ Abstract ]: This paper briefly describes the VGA interface and its display principle, and introduces the specific method of implementing the VGA interface using the SM501 graphics acceleration chip in an ARM-based embedded system. [ Keywords ]: Embedded VGA interface, SM501 Introduction Embedded products generally use two display methods: LCD and VGA (Video Graphics Array). Currently, most embedded development platforms in China use LCD screens for graphics display. Typically, LCD screens only support a maximum resolution of 800*600. Even with a VGA interface (through an adapter), it cannot smoothly play MPEG1 and MPEG4 multimedia files at high resolutions (1024*768*32). For some special industry applications, this cannot meet user needs. VGA, essentially an analog interface, is somewhat outdated in the digital age. However, in many industrial settings, VGA is generally chosen as the display method due to the following factors: 1. Industrial-grade LCDs are relatively expensive, and various LCD interfaces differ. 2. As a long-standing industry standard, the VGA interface is the standard interface for all display devices. This paper, in the process of developing a motion controller based on the S3C2440 embedded platform, successfully utilizes the technology from Taiwan's Silicon... Motion's high-performance 2D graphics acceleration chip, the SM501, combines the high-efficiency processing power of the S3C2440 with the graphics acceleration capabilities of the SM501. Through Microsoft's Windows CE 4.2 operating system, it can drive VGA interface displays. Considering the design requirements of embedded systems, this article only introduces the display specification with the lowest bandwidth: 640×480@60Hz. 2. Schematic Design The SM501 supports three different system configurations. Two of these are Unified Memory Architecture (UMA) modes, where system memory and frame buffer share memory resources. Figure 1 shows these possible configurations: Configuration A is the non-UMA mode, offering the highest performance. In this mode, system memory and frame buffer each have separate memory resources. The SM501 acts as a slave device controlling SDRAM, and it can also act as a master device accessing system memory. Configuration B is the UMA mode, where system memory and frame buffer share system memory resources, and the SM501 connects to the host as a slave device. It can also request the system bus and access the system SDRAM as a master device. However, this method has limited performance because the SM501 and the host need to time-share access to the system memory. Configuration C is a better option among UMA methods. In this mode, the local SDRAM contains system memory and frame buffers; the SM501 connects to the host as a slave device. When the local SDRAM runs at a 150MHz clock speed, the bandwidth of Configuration C is higher than that of Configuration B. [align=center]Figure 1 Hardware connection method between SM501 and the host[/align] Based on the above description, this system adopts the third scheme, which has the simplest hardware connection while meeting performance requirements. The connections between the SM501 and S3C2440 are relatively few. The main circuit is shown in the figure below: The hardware design of the VGA interface is as follows. Considering that the VGA interface is frequently plugged and unplugged while hot during use, a protection circuit needs to be added. The author uses a general Schottky diode to connect the BAV99-A7 to the three RGB lines: [align=center] Figure 3 VGA interface circuit diagram[/align] At the same time, some configuration pins of SM501 must be configured properly, otherwise SM501 will not work properly. The main pins that need to be configured are as follows: Local SDRAM row address size. When reset, it is determined by GPIO6 and GPIO5, but it can be changed by software. GPIO7 determines whether to reset the frequency divider. The level of GPIO12 determines whether to drive the MCS# pin. GPIO[15:13] determines the size of local memory (minimum 2MB, maximum 64MB). GPIO31, GPIO29 determine the host clock input source 3. Silicon Motion provides the SM501 software dynamic link library (including ARM, MIPS, x86, and other CPU architectures) for Windows CE, along with the corresponding source code and application documentation. In Samsung's Windows CE BSP based on the S3C2440, the default display device is the S3C2440A's on-chip LCD interface. Therefore, this default device needs to be removed and replaced with the SM501 dynamic link library. Using the SM501 in Windows CE requires the following steps: 1. Copy the SM501 dynamic library binary file to the directory "$(_WINCEROOT)\public\common\oak\DRIVERS\DISPLAY\SMIVGX\". 2. Import the VoyagerGX driver feature's CEC file into the PLATFORM BUILDER. 3. Add this feature to the generated Windows CE operating system project file. 4. Delete the driver description for the S3C2440A's on-chip LCD from the platform.reg and platform.bib files, and replace it with the driver description for the SM501. Compile the above steps; more detailed descriptions are available in Silicon Motion's documentation. Note that to add logo support during WinCE startup, the corresponding SM501 code needs to be added to the WinCE bootloader. 4. Summary After thorough experimentation, the following conclusions were drawn: The VGA interface graphics system based on S3C2440A+SM501 achieves 640×480@60Hz and can smoothly play various videos at up to 1024x768@85Hz without flickering, meeting system requirements. References [1] He Zongjian. WINDOWS CE Embedded System [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2006 [2] Wang Bing, et al. EVC Advanced Programming and Its Application Development [M]. Beijing: China Water Resources and Hydropower Press, 2005 Authors' Profiles : Xiao Yong: Male, Master of Mechanical Manufacturing and Automation, School of Manufacturing Science and Engineering, Sichuan University, Research Direction: Computer Numerical Control Technology Li Xianglong: Male, PhD in Mechanical Manufacturing, Associate Professor and Postgraduate Supervisor, School of Manufacturing, Sichuan University, Research Direction: Computer Monitoring and Industrial Equipment Automation, Computer Numerical Control Technology Zhang Yong: Male, Master of Mechanical Manufacturing and Automation, School of Manufacturing Science and Engineering, Sichuan University, Research Direction: Computer Monitoring and Industrial Equipment Automation