Study On The Operation System Used In The Measurement Instrument Based On Embedded Linux

With the development of the measurement technology, more and more instruments are requested to install operating system. At present, operating systems for instruments can divide into two categories: the operating system for desktop computer to use and embedded operating system.The former is mainly Windows serious, the later is commonly some commercial embedded operating systems, for example, Vxworks, WindowCE and so on.They often need to be paid of high license cost, which increase products'cost. Linux abided by GPL (General Public License).Having the advantage of open-code, free-cost, supporting different I/O, modularization and good network performance, it attracted more and more developers, Linux had been widely used in embedded systems.This dissertation is devoted to show the research and practice on the subject. The main contributions of the paper are shown below:To improve the real time performance of Linux. The dissertation analyzes the real-time disadvantages in Linux. Fortunately, most of Instruments is belong to soft real time system. We realize a new preemption kernel by adding preemption points in the kernel. The experimental result demonstrates that the real-time performance is effectively improved.Schedulability Test for periodic tasks with partial order constraint.The schedulability of real time processes not only depends on the scheduling algorithm, but also on the priority set of tasks. Static scheduling algorithm has the advantage of less payload, but it also has disadvantage of less flexibility. Dynamic scheduling algorithim need more payload, but it's schedulability is better than static scheduling algorithim, which demonstrate by examples. To our best knowledge, static scheduling is adopt by most embedded systems. There are many non-periodic tasks and hyper-period tasks with partial order constraints in measurements field, we put forward a schedulability test algorithm for these tasks in the system.To improve the network performance of linux. Two technologies are adopted to decrease the copy times between the kernel zone and the user zone: special static network communication resources allocating, as well as memory remapping mechanism to eliminate the data copies when receiving a packet.The security of instrument based Linux network. The paper discuss access control and auditing for instrument, Both of them is based on LSM(Linux Security Module). We improve LSM to realize light and contralable auditing. The architechture of 3G signal generator based on network is also designed.The software design of AV1486 Wave Signal Generator based on Linux. The main content included: modeling the AV1486's hardware, implementation of keyboard driver, implementation of YTO driver, realization of dot-frequency signal output, the design of GUIs. The result of experimental demonstrates that Linux may effectively support Wave Signal Generator.Measurement of the profile curve with CMM based on Linux. A method is advanced with which the operation can start to test a cam at any position. The cam profile is scanned only once and all sampling data is used to determine the work piece coordinate system, which make the error objective function minimum. A metrology method to revise the radius of switch probes is also put forward.