Abstract: This paper discusses the development of an OSD tool for digital television on the Hexin embedded operating system. EZCOM technology is used to build the OSD middleware, and an OSD development tool based on the SDA55XX chip is designed and implemented. Taking this chip as an example, the design concept, architecture, and OSD development method of the digital television OSD development tool are introduced in detail. Keywords: Embedded operating system, digital television, OSD tool. The biggest feature of digital television services is that, in addition to supporting traditional audio and video services, it also provides value-added television services, such as video-on-demand, data broadcasting, personalized interactive television, distance education, Internet, triple play, television e-commerce, and daily information integrated services. All value-added television services are built on strong software development capabilities. Among the many elements of digital television, the On Screen Display (OSD) system is the main thread running through the entire digital television application and value-added services. All value-added services and digital television control are presented to the user through the OSD. Therefore, OSD development is the most critical element in digital television software development. Currently, the operating systems and OSD development tools on these systems, bundled with chips and provided by foreign manufacturers, are commonly used in China. Due to the closed nature of foreign operating system technologies, domestic manufacturers will find it difficult to conduct independent development and must rely heavily on the technical support of foreign manufacturers. To better develop China's digital television industry, on the one hand, it is necessary to adopt operating systems with independent intellectual property rights; on the other hand, it is also necessary to accelerate the research and development of related technologies for digital television software platforms. Hexin Embedded Operating System is a research result of the 863 project "Networked Embedded Support Technology" and is an operating system with independent intellectual property rights. This project is part of the 863 project "Internet Operating System Based on Component and Middleware Technology and Cross-Operating System Component and Middleware Runtime Platform". Therefore, the research on the development of Hexin digital television OSD software in this paper not only has important theoretical significance but also broad application prospects. 1. Hexin Embedded Operating System and its Component Technology The Hexin Embedded Operating System technology system includes ezCOM component technology, component runtime platform technology, and the integrated development environment required for developing application software, forming a complete component-oriented application software development platform. Hexin is a 32-bit embedded operating system. The operating system is based on a microkernel and has characteristics such as multi-process, multi-threaded, preemptive, and thread-based multi-priority task scheduling. It provides a FAT-compatible file system and can boot from floppy disks, hard disks, Flash ROMs, and networks. The system is small and fast, suitable for most embedded information devices in the network era. The Hexin operating system is entirely component-based, with all functional modules based on ezCOM component technology, making them removable components. Application systems can be tailored and assembled as needed, or necessary components can be dynamically loaded at runtime. From the perspective of traditional operating system architecture, the Hexin operating system can be seen as consisting of a microkernel, component support modules, and a system server. 2. Introduction to the SDA55xx Chip The SDA55xx microcontroller is a television chip produced by Micronas, primarily used for television control and providing graphic image display. The SDA55xx not only provides decoding of the World System Teletext (WSrl) function but also supports decoding of other systems such as the Video Programming System (VPS), Program Delivery Control (PDC), and Widescreen Signalling (WSS) for PAL-plus (European New Television Broadcasting System). The SDA55xx data splitter and display section support a wide range of television standards, including PAL, NTSC, and the aforementioned VPS, WSS, PDC, TTX, and Closed Caption Data. 3. Design of the DTV OSD Tool 3.1 Design Philosophy The DTV OSD Developer is a visual development tool built on the DIV middleware platform. Based on the characteristics of digital television software development, it encapsulates frequently used objects in interface design into controls for easy user access. The user interface framework seen during development is essentially the same as the interface during program execution. This allows software design to be completed without a physical device, avoiding the need for extensive time spent repeatedly downloading programs to the chip and frequent power-on debugging, thus improving software development efficiency. 3.2 System Architecture The embedded operating system and the DTV software development platform middleware constitute the development and operation environment for a digital television system based on an embedded operating system. The upper-level application interface of the embedded real-time operating system and devices controls the corresponding devices through drivers and provides system services to the middleware. In digital television software systems, the DTV software platform middleware provides runtime support for application software based on the operating system. Simultaneously, it appropriately encapsulates the device control interfaces provided by the operating system. This new interface decouples the high degree of coupling between different application providers and specific hardware and software details in different digital televisions, thus enabling content to be created only once and run "anywhere." The DTV software development platform adopts a three-dimensional hierarchical structure, running as a system component on the operating system middleware platform. Since the interaction between the component and external applications and the operating system is entirely through interfaces, it ensures that the implementation details of the component do not affect the programs using it, allowing it to continuously add new functions and requirements based on functional needs and supported application types. Its hierarchical structure is shown in Figure 1. 3.3 OSD Development Based on SDA55xx In OSD development based on SDA55xx, since the only development materials available were the detailed datasheet and development environment for SDA55xx provided by Miemnas, including a Windows integrated development environment (WINIDEA) and an emulator device, all development started from scratch. To develop an OSD system based on SDA55xx, one must be familiar with the DATASHEET, master the functions of its internal special registers, the allocation of internal XRAM, the structure of DRCS, and the construction method. Based on these conditions, the author designs the OSD development based on SDA55xx as follows: (1) OSD design stage. The main focus is on OSD interface design. The OSD interface designed at this stage is the final interface presented to the user, so it has high requirements for aesthetics and practicality; (2) Module design stage. Based on the OSD interface designed in the OSD design stage, the main elements included are analyzed, and then the drawing of each element is encapsulated into modules. The main tasks of this stage are: to clarify the elements in the style OSD interface, define the structure of each module, etc.; (3) Specific implementation stage. This stage mainly implements the drawing function of each module. Its work is to allocate XRAM, construct DRCS, and configure special registers. After the module drawing function is implemented, the main program calls the drawing module to complete the OSD menu system. Figure 2 is the basic system structure. In this structure, both the OSD interface and module design are very important, but the main work is the final construction of DRCS, the allocation of XRAM, and the assignment of special registers. 3.4 System Composition DTV Visual Developer mainly consists of four workspaces: (1) OSD TreeView: This is the main place for editing menu states. The menu states are represented by a tree structure, and the relationship between parent and child menus is simulated through the relationship between parent and child nodes. (2) Menu Designer: This is the workspace for user interface design. The user interface framework designed here is basically the same as the graphical interface when the program is running. It provides functions for adding, deleting, and adjusting the shape and position of controls. (3) Window: Each item corresponds to a menu state. It contains all controls in this menu state, whether the control is visible or invisible. (4) Properties Window: This allows editing various properties and behaviors of the selected control. In addition, DTV Visual Developer also provides user-friendly functions such as variable tables, string tables, and color tables. At the same time, this integrated development environment is also configurable. For example, the types of controls, the properties of each control, and the font library used in the program can all be customized according to the user's needs. This ensures the flexibility and adaptability of the development tools. 3.5 Design Considerations for DTV OSD Developer In DTV OSD Developer, all menu states are abstracted as tree nodes in an OSD TreeView, with each state corresponding to a unique number. Except for the last two digits, each subsequent two digits represent a menu level. For example, "01FFFFFF01" indicates a maximum menu depth of four levels in this program, while the last two digits represent the channel corresponding to this menu state, such as 01 for TV, 02 for AV, etc. The first few digits of the submenu state number should match the corresponding digits of the parent menu state number. For example, the first submenu number of menu state "01FFFFFF01" should be "0100FFFF01". This allows for convenient scheduling when the program jumps between menu states using their state numbers. Each menu state is encapsulated into an enumeration structure. For example, the main menu state under the TV channel can be represented by the following structure: When the main program searches for a menu state, it can locate an array structure through the state number, and then find the memory address and number of the corresponding substate based on this structure. For example, the main menu array structure under the TV channel is as follows: 4. Digital TV Software Development Method Based on DTV OSD Developer In the process of developing digital TV software using the visual development tool DTV OSD Developer, all DTV applications are abstracted into a control set + resource set pattern, as shown in Figure 3. This development model means that the implementation of software functions is no longer marked by the implementation of individual functional modules, but rather follows the process of "creating a user interface – setting the properties of control objects – writing event response code". This not only greatly improves the efficiency of software development, but also makes the developed applications more logical and easier to maintain. This paper, combined with the 863 project "Internet Operating System and Cross-Operating System Component and Middleware Runtime Platform Based on Component and Middleware Technology", develops an OSD middleware based on ezCOM on the Hexin embedded operating system, ultimately forming an OSD development method under a five-layer system architecture: OSD application, OSD middleware, Hexin component runtime platform, Hexin operating system, and hardware platform, and implementing a fully component-based system architecture. By using the OSD software system for development, many specific implementation details are isolated, allowing for the customization of unique OSD software in a simple way. This improves development efficiency, reduces development costs, keeps pace with technological advancements, makes application development more convenient, and enhances the openness and portability of products.