Abstract: Miniaturization, modularization, and remote control capabilities of electrical systems are the requirements for the further development of photoelectric tracking equipment. This paper mainly introduces a remote control system based on DSP and embedded X-BOARD processor, constructed using an Ethernet + embedded system mode. The paper focuses on the software design, hardware composition, and implementation method of real-time data exchange and control with the DSP via Ethernet. Based on this, a miniaturized, modular, and remotely controllable control system was developed. The system consists of a DSP real-time control module and an embedded interface submodule. The former connects to the data acquisition path and PWM driver stage, while the latter, under the VxWorks real-time operating system, completes the transmission and reception of Ethernet data and the exchange of real-time data with the DSP. Verified on a tracking control platform, the system meets the requirements for remote control and has significant advantages. Keywords: Remote control; Embedded processor X-BOARD; Ethernet; Photoelectric tracking 1 Introduction With the development of embedded computing technology, embedded processors and real-time operating systems have been widely used. Control systems not only place further demands on miniaturization, modularity, and real-time data processing, but also often require the ability to achieve remote control. Ethernet’s advantages such as long-distance transmission and high data transmission bandwidth have led it to gradually enter the traditional control field. Embedded systems, with their small size, multiple functions, and high reliability, have become a new hot spot in the industrial control field. VxWorks is a real-time operating system launched by Wind River Corporation of the United States. It is widely used in high-precision technology and high real-time fields such as communication, aviation, and aerospace, such as satellite communication and aircraft navigation, due to its good reliability and excellent real-time performance. X-BOARD is a next-generation embedded processor module launched by Kontron Corporation of Germany. It is very powerful and integrates almost all the application interfaces needed today, such as USB, Ethernet, PCI, LPC, etc. [1]. Its excellent embedded characteristics are reflected in low power consumption, small size, no need for external heat dissipation devices, considerable openness to various architecture CPUs, and easy performance upgrades. Photoelectric tracking control system is a typical embedded system application. Research on its remote control is of great significance. This paper adopts a client and server mode and realizes real-time communication and control between the remote master computer and the DSP based on the embedded X-BOARD<861> processor and VxWorks real-time operating system. 2 Control System Composition The remote control system is based on a photoelectric tracking control platform, and its system structure is shown in Figure 1: Figure 1 Remote Control System Structure In the entire remote control system, the client program runs on the remote master computer, which performs DSP dynamic program loading, system operation status monitoring, real-time control parameter transmission, and network connection reporting via Ethernet; the server program runs on the embedded submodule, which is responsible for real-time data exchange between the remote master computer and the DSP; the DSP adopts the low-power high-speed DSP TMS320C5416 from TI, with a working frequency of up to 160MHz. In order to ensure the real-time operation of the entire system, the following mechanism is adopted: the real-time control algorithm runs on the DSP, while the embedded submodule and the remote master computer only perform system background operation. The fast reflector is a precision tracking technology. It, together with the spindle system of the large inertia frame structure, constitutes a composite axis tracking system, which is mainly used to correct the tracking error of the spindle system and the line-of-sight jitter caused by wind torque, foundation, frame and atmospheric interference [5,6]. The position information of the fast reflector is obtained by sampling the voltage output value of the eddy current sensor, and the rotation of the fast reflector is driven by the voice coil motor. From the above discussion, we can see that the embedded submodule design is the key to the whole remote control system. Its hardware structure principle is shown in Figure 2: Figure 2 Embedded submodule structure The X-BOARD<861> embedded processor module has 128Mbyte SDRAM and uses AMD Geode SC1200 CPU. The CPU is based on the X86 architecture and has a main frequency of 266Mhz, which provides a good guarantee for the timely response of the system. After actual testing, it only takes about 750ns from the interrupt initiated by the FPGA to the interrupt response, and it can handle up to 20KHz interrupts under the VxWorks operating system. X-BOARD expands the bus through the PCI 9054 bridge chip, and the FPGA is the PCI local terminal. Due to the inconsistency between the PCI bus and the DSP interface speed, all data exchange is buffered through the dual-port SRAM defined inside the FPGA. 3 Software design Socket is an interface defined by BSD UNIX for applications to use the TCP protocol. Many operating systems, including VxWorks, use the socket interface [3]. This remote control system employs the reliable data stream SOCK_STREAM based on the TCP protocol. It provides ordered bidirectional byte streams and out-of-band data transmission capabilities. Each complete transmission involves establishing a connection, using the connection, and terminating the connection, thus ensuring data transmission reliability. Besides determining the underlying network transmission protocol, the client and server software should also design their own data transmission protocols to parse complex control commands, debug parameters, program loading data, and control parameters. In this system software design, all data is transmitted in 1001-byte packets, with the last 1000 bytes being valid data and the first byte being a control word. When a data packet is received, the first byte is extracted, and the appropriate processing method for that frame is determined. The software design primarily focuses on the client and server software. The client software development was completed in the VC++ 6.0 integrated development environment, and its software structure design is shown in Figure 3. A child thread receives data sent from the server and passes it to the main thread via a message queue. The main thread processes local commands and data passed from the child thread. Local commands refer to commands issued by operators through the client's human-machine interface, mainly including DSP program loading, reset control, PWM blocking and unlocking, control parameter adjustment, and background data recording. Taking the DSP program loading process as an example, this section details how the client and server interact with commands and data. First, the loading file is read into the buffer, and then the data is packaged and sent to the server. After receiving the data packet, the server first extracts the control word, identifies it as a program loading data packet, and then loads the DSP program through the handshake signals XF and BIO. The data packets received by the sub-thread mainly include four channels of debugging parameters and four channels of error data. After receiving the data packets transmitted by the sub-thread, the main thread also first extracts the control word and then determines what operation to take. Figure 3 shows the client software design flowchart. The server-side software development was completed in the VxWorks integrated development environment Tornado 2.2. Compared to the client software, the server-side software needs to perform more tasks, such as interrupt handling, PCI driver, protocol parsing, and handshake with the DSP. However, due to the powerful functions of the Tornado 2.2 development tool, all requirements can be easily developed. The server-side software structure design is shown in Figure 4. [align=center]Figure 4 Server-Side Software Design Flowchart[/align] As shown in Figure 4, the server-side software is based on a multi-task design. The main task first initializes the PCI driver and network, and then accepts client connections in a cyclical manner, hatching corresponding data reception and transmission subtasks. The data reception subtask receives data and commands from the client, processes them accordingly after protocol parsing, and the PCI interrupt service routine only performs semaphore release operations to notify the data transmission subtask to read data from the dual-port RAM and send it to the client. 4 Actual Control Experiment Figure 5 is a schematic diagram of the experimental platform structure. After actual control verification, this system can achieve point-to-point data transmission over a distance of approximately 20 meters, with network data traffic reaching 1.25 Mbps during operation. The background can record up to 30 MB of running data at a time for post-event analysis. The client can simultaneously monitor four debugging parameters, four error data, and the network data traffic trend, and can adjust four control parameters in real time. [align=center]Figure 5 Schematic diagram of the test platform[/align] Figure 6 shows the closed-loop process of the fast reflector's X-direction position via the eddy current signal, plotted based on data recorded by the remote control system client. The upper part of the figure shows the eddy current variation curve, and the lower part shows the control quantity variation curve. After testing at a 10K sampling rate, the system operated stably with no packet loss in data transmission. [align=center]Figure 6 Closed-loop test of the fast reflector's position[/align] 5 Conclusion The innovation of this paper lies in fully utilizing the high real-time performance of the VxWorks operating system, the small size and high performance of the KONGChuang X-BOARD<861> embedded processor module, and the long-distance, high data transmission bandwidth characteristics of traditional Ethernet to construct a complete remote control system, generating approximately 500,000 yuan in economic benefits annually. The paper details the hardware and software design of the entire system and the subsequent test platform architecture, and presents the actual control results. This system has good versatility and can be easily applied to most situations requiring remote control. After testing and verification, the system can fully meet the current control requirements, ensure the realization of various functions, and provide a new way for the further miniaturization and modularization of photoelectric tracking equipment. References: [1] X-board 861 Manual R120 [Z], 2004, Kontron. [2] VxWorks network programmers guide 5.5 [Z], 2003, WindRiver System Inc. [3] Li Fangmin, Advanced VxWorks Programming [M]. Beijing: Tsinghua University Press, 2004. [4] Li Feng, Ying Hong, Zhang Jun. Using TCP/IP to realize communication between Windows and VxWorks [J]. Microcomputer Information, 2006, Vol. 22, No. 5: 21-23. [5] Ma Jiaguang, Basic technical problems of capture, tracking and aiming system [J]. Optoelectronic Engineering, March 1989, Vol. 16, No. 3: 1-41. [6] Fu Chengyu, Jiang Lingtao, Ren Ge, et al. Fast reflector imaging and tracking system [J]. Opto-Electronic Engineering, March 1994, Vol. 21, No. 3: 1-8.