Abstract: This paper designs a gyroscope measurement and control system based on a 32-bit ARM chip S3C44B0X and a Clinux operating system. The system performs functions such as measurement, transmission, display, modification, and fault alarm of various gyroscope parameters, realizing the monitoring and control of the gyroscope. Keywords: measurement and control system; ARM; gyroscope; Clinux 1 Introduction Embedded systems are dedicated computer systems that use embedded computers as their core technology. They are user-, product-, and application-oriented, with customizable hardware and software, and are suitable for applications with strict requirements on functionality, reliability, cost, size, and power consumption. With the continuous development of information technology, embedded systems have been widely used in various industries such as scientific research, engineering design, military technology, and people's daily lives. This design selects an embedded system as the measurement and control system for a gyroscope, which greatly improves the system's accuracy, flexibility, ease of operation and program modification, and also provides a good solution for further improving the system's functions in the future. 2 Introduction to the Design Scheme of the ARM-based Gyroscope Measurement and Control System [align=center] Figure 1 System Design Scheme Diagram[/align] The entire measurement and control system is divided into two major hardware modules (as shown in Figure 1), namely the ARM-based parameter measurement and control module and the ARM-based human-machine interaction module. The parameter measurement and control module realizes the acquisition and correction of various parameter values, adjusts the output control voltage according to the measured gyroscope rotor frequency data, responds to user input control parameters, adjusts commands, and automatically diagnoses faults. The rotor frequency requires high measurement accuracy in the measurement and control system, so FPGA is used for frequency measurement. The human-machine interaction module realizes the display of parameters, the input of control parameters, and fault alarms. The human-machine interaction computer needs to receive system status information sent by the control host and display it in graphical or textual form. Meanwhile, the control host adjusts the system according to the control parameters transmitted by the human-computer interaction computer. Communication between the two computers is completed through a serial communication interface. The embedded operating system Clinux provides a high-performance software running platform for advanced applications. 3 System Hardware Design The hardware platform of this design adopts an embedded system based on the S3C44B0X. The S3C44B0X is a 32-bit embedded processor with an ARM7 core, which internally has 8 channels of 10-bit A/D, 71-pin general purpose input/output ports, 2 asynchronous serial ports, an on-chip calendar, an on-chip 16-bit PWM timer, a watchdog timer, an LCD controller, and a JTAG debugging interface. Combined with peripheral memory, power supply, and other chips, it constitutes a complete embedded system. The gyroscope parameters to be measured in this system mainly include the gyroscope rotor frequency, voltage and current signals, and the internal temperature of the gyroscope. Since the stability of the gyroscope rotor frequency affects the gyroscope accuracy, the XC3S200 chip is used as the core device of the frequency measurement circuit to specifically complete the accurate measurement of the rotor frequency. The XC3S200 is an FPGA chip manufactured by Xilinx, featuring high precision and stability, meeting the system design requirements. Voltage and current parameter measurements are acquired by the S3C44B0X's 8-channel 10-bit on-chip A/D converter and sent to the CPU. The voltage signal, being bipolar, is limited and shifted by operational amplifier OP07 to obtain a unipolar signal of 0–2.5V, meeting the A/D acquisition requirements. The current signal is first converted into a voltage proportional to the current by a Hall effect sensor, then sent to the analog-to-digital converter via operational amplifier circuitry. The internal temperature of the gyroscope is measured using a bridge amplifier circuit. The outputs of the bridge are amplified to obtain the output voltage, which is then input to the S3C44B0X's built-in A/D converter. The human-machine interface module includes the S3C44B0X microprocessor, memory, serial communication interface, a 320×240 resolution LCD display, a 6×6 keypad with status indicators, and a buzzer. This module allows monitoring of the gyroscope's operating status and adjustment of control parameters at any time. According to the system design requirements, the control host and the human-machine interface computer are some distance apart. To ensure data reliability and circuit simplicity between the two computers, a serial port is used for data exchange. The serial port circuit consists of a serial port controller, an RS232 serial communication adapter chip MAX232, and a serial port connector. 4 System Software Design The system software includes the device drivers included with the operating system, the operating system runtime environment, user-defined device drivers, a middleware interface program that encapsulates the low-level drivers, and high-level application programs. In the software design, the entire application is divided into different layers, implemented in the driver layer, middleware layer, and high-level application layer programs respectively. 4.1 Operating System The operating system of this system uses the embedded operating system Clinux. Clinux is derived from the Linux kernel, with appropriate trimmings and optimizations based on the standard Linux. Clinux has advantages such as easy configuration, small size, stability, good portability, complete support for various file systems, support for drivers of common embedded chips, and a rich set of standard APIs. Developing custom applications based on this foundation can further improve efficiency and offer excellent portability. Given these advantages, and considering the actual situation of this system, choosing Clinux as the operating system is quite suitable. 4.2 Device Drivers In the design and development of this system, in addition to the device drivers provided by the operating system, custom device drivers need to be written to add new external devices to meet the system's design requirements, enabling the devices to be supported by the operating system. In this system, custom drivers were written for character devices such as A/D, D/A, and serial ports. Device drivers are the interface between the operating system and hardware devices; the kernel uses this interface to request the driver to control the device's I/O operations. Device management in Clinux uses the concept of device files to unify the device access interface. Therefore, users access any device just like ordinary files; users can open and close device files and perform data reading, writing, and other operations. The device driver interface looks the same as the file system interface, i.e., the structure `file_operations{}`. For character devices, `file_operations{}` is the only function interface. When writing custom device drivers, only interface functions that are meaningful to the user need to operate the device. Taking the custom A/D device driver in this system as an example, the basic structure of `file_operations{}` is as follows: `struct file_operations ADC_fops = { llseek: NULL, //lseek read: NULL, //read write: NULL, //write readdir: NULL, //readdir poll: NULL, //poll ioctl: ADC_ioctl, //ioctl mmap: NULL, //mmap open: ADC_open, //open release: NULL, //release fsync: NULL, //fsync fasync: NULL, //fasync };` When the system calls these operations, it will automatically use the corresponding functions in the `file_operations{}` structure to implement the specific operations such as `open` and `ioctl` on the A/D device. In addition, another important aspect of writing a device driver is driver initialization. int init_ADC(void) { int result; result = register_chrdev(252,"ADC",&ADC_fops); if (result<0) printk("(ERROR):Register ADC device failed!\n\n\n"); printk("(Devices):Register ADC device succeed!\n"); … } The function register_chrdev() registers the character device, after which normal device access can be performed. 4.3 The intermediate layer interface program encapsulates the underlying driver. The serial communication module encapsulates the communication protocol and mainly realizes data exchange between two computers. This module is built on the operating system driver and further adopts multi-process technology to buffer the data received from the serial port driver, cut it into a custom protocol encapsulation form, and finally assemble it into a format that is convenient for high-level applications to use, providing application programming interface (API) functions for high-level applications. The serial port module program flow is shown in Figure 2. [align=center]Figure 2 Serial Port Module Program Flow[/align] The serial communication module transmits data in the form of data frames, which are then packaged and sent and received. The definition of a frame is the data format of the sending and receiving ends, ensuring that the receiving end can accurately retrieve valid data. Struct UartDataFrame { Char StartFlag; Char Index; //Data frame sequence number Char Dealed; //Whether this group of data has been processed (sent or interpreted) Char Type; //Frame data type char Data[DATA_CONTENT_SIZE]; //Original data char Reserved; char EndFlag; } This serial port underlying transceiver encapsulation program module uses a three-level circular buffer: the first level is used to store each received single character; the second level is a circular buffer composed of bytes, which places the data received from the first level buffer in the order of reception; the third level cuts the data in the second level buffer into frames and stores them, and also provides supporting functions for accessing frame data. Serial communication appears as an independent module in the system. The serial port API provides a clear functional interface for high-level applications, offering three functions for serial port initialization, data extraction, and data transmission. During initialization, the high-level application calls the initialization function to initialize the serial port module, putting it into working condition. The serial port module combines and organizes the received data, storing it in a buffer. The high-level application then calls the data extraction function, retrieving the data from the buffer for processing. Correspondingly, the high-level application populates the fields of the `struct UartDataFrame` variable and passes the pointer to this variable to the serial communication module. The serial communication module buffers the data to be sent and sends it out in a queue. 4.4 High-Level Applications 4.4.1 High-Level Applications for the Control Host The control host primarily performs parameter measurement and gyroscope control. Due to the need to manage various devices and implement complex logic control functions, the design of the high-level applications draws on object-oriented programming methods. Based on the module functions of the high-level application layer, they are abstracted into program objects. Each object has its own resources and can perform the functions of a specific module. Communication between objects enables collaborative work between modules. The program defines the following classes: CLASS_Freq_Measurement //Frequency measurement module; CLASS_DAC_Module //D/A conversion module; CLASS_Control_Module //Control module; CLASS_System_State_Module //System state module; CLASS_Alert_Module //Alarm module. The advanced application is centered on the control algorithm, with multiple tasks serving the control. The serial data communication module employs multi-process technology to ensure timely and smooth communication. The system kernel periodically measures each channel in a time-division manner and passes the measured data to the advanced application through callback functions. The advanced application only needs to perform simple operations to extract the data and perform corresponding subsequent operations. 4.4.2 Implementation of the Advanced Application Based on Microwindows Graphical Interface The advanced application of the human-computer interaction module is a graphical interface application based on Microwindows. Microwindows is an open-source embedded GUI software designed to bring a graphical window environment to small platforms running Linux. It allows designers to easily incorporate various display devices, mice, touchscreens, and keyboards while utilizing less RAM and file storage space; the application code can be implemented in C language, offering excellent portability; and it supports ARM-based processor chips. The basic structure of a high-level application based on Microwindows consists of initialization, window and resource creation, and message loop entry. In this system's graphical interface high-level application, the message loop includes the function `PeekMessage()` to retrieve messages from the message queue, a serial port receive buffer query function, and a keyboard buffer query function. After application initialization, these three functions are executed repeatedly, and message processing functions are executed upon receiving a message. 5. Conclusion The innovation of this paper lies in the research and design of an ARM-based gyroscope measurement and control system. This system, based on an S3C44B0X microprocessor and a Clinux operating system, completes the measurement, transmission, display, modification, and fault alarm functions for various gyroscope parameters, realizing the monitoring and control of the gyroscope. Furthermore, the system has a user-friendly human-machine interface, facilitating monitoring and operation, and provides a good solution for further system function improvement and expansion. This system has undergone long-term continuous operation experiments and works normally, meeting the design requirements. References: [1] Li Shanping, Chen Wenzhi, et al., "LINUX Kernel Guide", Hangzhou: Zhejiang University Press, 2002 [2] Samsung, "S3C44B0 Microprocessor - Product overview" [3] Zhou Ligong, Chen Mingji, Chen Yu, et al., "ARM Embedded Linux System Construction and Driver Development Examples", Beijing: Beijing University of Aeronautics and Astronautics Press, 2006 [4] (US) Charlie Calvert, "21 Days to Windows Programming", Beijing: Electronic Industry Press, 1995 [5] Zhang Jin, Wang Yongliang, Frequency Data Acquisition and Sharing in Embedded Systems Based on ARM7, [J] Microcomputer Information, No.11: 82-83, 2006