Design Of Portable Digital Oscillograph Based On ARM

With the development of the electronic measuring technology, the demand for measurement technique is higher and higher, so the traditional electronic oscillograph can hardly satisfy the need for real works. Measuring technology is geared to automated, intelligent and network directions. Digital storage oscillograph as the important measuring apparatus is widely used in various fields.The design of digital storage oscillograph is based on the embedded systems. In recent years, the rapid development of digitization technology centering on computer, chip technology and software engineering, greatly boosts the research of embedded technology. Powerful embedded processor and excellent embedded operating system have been developed successively, which makes the application of embedded system more and more widespread and contains each aspect of national economic construction.Embedded systems include embedded processor and embedded operating system. Embedded processors and the related functional expansion of the system's circuit structure the hardware platform. Embedded operating systems include the bottom-driven software associated with hardware, system kernel, device driver, communication protocols, a graphical interface, standardization browser and so on. Embedded operating system runs on the embedded processor. Embedded operating system administers the processor and other hardware equipment in the bottom of processor, and it operates all application procedures. It shields the bottom of the details to provide a unified user interface. Application developers only need to split system development into several independent modules. This has greatly simplified the application design and shortened the development cycle, reduced repeating work, improved the efficiency of product development and improved the efficiency of knowledge innovation.Now the technology of digital storage oscillograph is more advanced overseas, and occupies the great majority of market. So it is indispensable to develop digital storages oscillograph ourselves. However, with the development, it can't meet the need of modern manufacture more and more. As a result, a handhold digital storage oscillograph is studied. According to these requirements, the portable digital oscillograph which can replace the general digital oscillograph is designed and realized in this paper.General application of ARM processor and development of embedded operating system provide new ideas for oscillograph design.The portable digital oscillograph designed in this paper is based on the embedded Linux OS and adopts Intel XScale PXA255 processor. It integrates the functions of signal collecting, data calculation, data communication, data storage and signal display. The system design is based on the cooperation of the hardware and the software. The system design and implementation process can be divided into the following steps :1. This system makes use of the Intel XScale PXA255 processor. We have designed the interface circuit of PXA255 processor and Flash, SDRAM, LCD and the touch screen A/D ADS7843 interface. Synchronously, I have designed the data collecting system hardware and realized the hardware platform of digital storage oscillograph system. Intel XScale PXA255 is a high-powerful embedded ARM processor introduced by Intel Corporation. It supports virtual memory management with MMU, pipelining, cache and the highest working frequency can be up to 400MHz; LCD do the terminals'display; Touch Screen Module uses AD7843; Terminal uses 32M bytes of FLASH and 64M bytes of SDRAM to store date and operate procedures, and the type are E28F128J3A and K4S281632C.2. This embedded system adopts Linux2.4.18 as the EOS (Embedded Operation System). Linux is organized with layer structure and opens its source code. Its network is power. And it supports many kinds of file systems and can operate on many kinds of embedded processors, including PXA255 processor.The embedded Linux OS is the heart of the whole system which controlls the operation of the whole system, and distributes the whole resource. The building of the embedded OS is the most important and complicated step which involves whether the whole system could operate reliably.After studying the boot process of Linux OS and the particularity of the embedded system, this system decides to use host/target cross-platform development mode. In this mode, the host takes charge of building cross-platform development environment and completes most of the development work. At last, the binary code is downloaded to the target platform and run.Besides, this system uses U-boot1.1.2 as the boot loader and makes JFFS2 (Journaling Flash File System) to be root file system. In software development, NFS (Network File System) is used to share file with PC. The above parts construct the basic embedded system software platform for software development and debugging.3. After the building of the software platform, I begin to program the applications for the digital storage oscillograph system. The applications mainly achieve the signal collecting, data storage and signal display functions. The study of application is based on the MiniGUI, and the next step is transplanting MiniGUI into the terminal platform to realize the GUI of it.Through debugging and testing, the hardware and embedded Linux operating system run stably, the GUI is friendly, the system carries out a good result of signal display and ultimately reaches the design request. The applications based on the embedded Linux OS are great transplantable, so we can transplant the applications of this system into other hardware platform. The system can be further expanded in terms of software and hardware to use in many other occasions.