基于ARM的串行端口通信翻译

基于ARM的串行端口通信翻译 职场大变样社区(www.zcdby.com):下载毕业成品 全套资料，全部50元以下 英文原文 Characteristics 1. Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real-time performance constraints that must be met, for reasons such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs. 2. Embedded systems are not always standalone devices. Many embedded systems consist of small, computerized parts within a larger device that serves a more general purpose. 3. The program instructions written for embedded systems are referred to as firmware, and are stored in read-only memory or Flash memory chips. They run with limited computer hardware resources: little memory, small or non-existent keyboard or screen. Processors in embedded systems Secondly, embedded processors can be broken into two broad categories: ordinary microprocessors (μP) and microcontrollers (μC), which have many more peripherals on chip, reducing cost and size. Contrasting to the personal computer and server markets, a fairly large number of basic CPU architectures are used; there are Von Neumann as well as various degrees of Harvard architectures, RISC as well as non-RISC and VLIW; word lengths vary from 4-bit to 64-bits and beyond (mainly in DSP processors) although the most typical remain 8/16-bit. Most architectures come in a large number of different variants and shapes, many of which are also manufactured by several different companies. Ready made computer boards PC/104 and PC/104+ are examples of standards for ready made computer boards intended for small, low-volume embedded and ruggedized systems, mostly x86-based. These are often physically small compared to a standard PC, although still quite large compared to most simple (8/16-bit) embedded systems. They often use MSDOS, Linux, NetBSD, or an embedded real-time operating system such as MicroC/OS-II, QNX or VxWorks. Sometimes these boards use non-x86 processors. However, most ready-made embedded systems boards are not PC-centered and do not use the ISA or PCI busses. When a System-on-a-chip processor is involved, there may be little benefit to having a standarized bus connecting discrete components, and the environment for both hardware and software tools may be very different. Peripherals Embedded Systems talk with the outside world via peripherals, such as: , Serial Communication Interfaces (SCI): RS-232, RS-422, RS-485 etc. , Synchronous Serial Communication Interface: I2C, SPI, SSC and ESSI (Enhanced Synchronous Serial Interface) , Universal Serial Bus (USB) , Multi Media Cards (SD Cards, Compact Flash etc.) , Networks: Ethernet, LonWorks, etc. , Fieldbuses: CAN-Bus, LIN-Bus, PROFIBUS, etc. , Timers: PLL(s), Capture/Compare and Time Processing Units , Discrete IO: aka General Purpose Input/Output (GPIO) , Analog to Digital/Digital to Analog (ADC/DAC) , Debugging: JTAG, ISP, ICSP, BDM Port, BITP, and DP9 ports. Tools As with other software, embedded system designers use compilers, assemblers, and debuggers to develop embedded system software. However, they may also use some more specific tools: , In circuit debuggers or emulators. , Utilities to add a checksum or CRC to a program, so the embedded system can check if the program is valid. , Custom compilers and linkers may be used to improve optimisation for the particular hardware. , An embedded system may have its own special language or design tool, or add enhancements to an existing language such as Forth or Basic. , Another alternative is to add a real-time operating system or embedded operating system, which may have DSP capabilities like DSPnano RTOS. , Modeling and code generating tools often based on state machines Software tools can come from several sources: , Software companies that specialize in the embedded market , Ported from the GNU software development tools , Sometimes, development tools for a personal computer can be used if the embedded processor is a close relative to a common PC processor As the complexity of embedded systems grows, higher level tools and operating systems are migrating into machinery where it makes sense. For example, cellphones, personal digital assistants and other consumer computers often need significant software that is purchased or provided by a person other than the manufacturer of the electronics. In these systems, an open programming environment such as Linux, NetBSD, OSGi or Embedded Java is required so that the third-party software provider can sell to a large market. Debugging Embedded debugging may be performed at different levels, depending on the facilities available. From simplest to most sophisticated they can be roughly grouped into the following areas: , Interactive resident debugging, using the simple shell provided by the embedded operating system (e.g. Forth and Basic) , External debugging using logging or serial port output to trace operation using either a monitor in flash or using a debug server like the Remedy Debugger which even works for heterogeneous multicore systems. , , An in-circuit debugger (ICD), a hardware device that connects to the microprocessor via a JTAG or Nexus interface. This allows the operation of the microprocessor to be controlled externally, but is typically restricted to specific debugging capabilities in the processor. , An in-circuit emulator (ICE) replaces the microprocessor with a simulated equivalent, providing full control over all aspects of the microprocessor. , A complete emulator provides a simulation of all aspects of the hardware, allowing all of it to be controlled and modified, and allowing debugging on a normal PC. Because an embedded system is often composed of a wide variety of elements, the debugging strategy may vary. For instance, debugging a software- (and microprocessor-) centric embedded system is different from debugging an embedded system where most of the processing is performed by peripherals (DSP, FPGA, co-processor). An increasing number of embedded systems today use more than one single processor core. A common problem with multi-core development is the proper synchronization of software execution. In such a case, the embedded system design may wish to check the data traffic on the busses between the processor cores, which requires very low-level debugging, at signal/bus level, with a logic analyzer, for instance. 英文翻译 嵌入式系统的特点: 1.嵌入式系统设计的目的是做一些特定的任务，而不是一个多任务的通用计算机。有的还必须满足的实时性的约束，如安全性和可用性;其它的可能有比较低或无特殊的性能要求，从而使系统硬件得以简化，降低成本。 2.嵌入式系统并不总是独立的设备。许多嵌入式系统是由一个服务于其它目的的较大设备中的计算机化的小部分组成。 3.嵌入式系统的程序通常被称作固件，并存储在只读存储器中或闪存芯片。他们运行在有限的计算机硬件资源上:内存小，很小或不存在键盘或屏幕 嵌入式系统的处理器: 其次，嵌入式处理器，可分为两大类:普通微处理器(μP)，微控制器(μC)，其中微控制器的芯片上有很多外设以降低成本和尺寸。个人电脑和服务器市场对比鲜明的是，嵌入式系统的微处理器应用了相当多形势的CPU基本架构;有冯•诺伊曼，以及不同程度的哈佛架构，RISC的以及非RISC，VLIW字长从4位到64位甚至更多(虽然最典型的是64位)。及以后的(主要是在DSP处理器)保持8/16-bit。最架构来在大量不同的变种，形状各异，其中有许多是由几个不同的公司生产的...... 准备好制造的电脑主板 PC/104和PC/104 +作为一个的例子，是旨在为小型，低容量，嵌入式和坚固耐用的，大多是基于x86的系统服务的电脑板。这些往往是小到可以和一个标准的PC相比，尽管和简单的嵌入式系统相比还是相当大。他们经常使用的MSDOS,Linux，NetBSD，或一个嵌入式的实时操作系统，例如MicroC/ OS-II，QNX或VxWorks等。有时，这些板使用非x86处理器。 然而，最容易实现的嵌入式系统板并不是以PC为中心的，并且不使用ISA或PCI总线。当系统具有一个单芯片上的系统处理器时，有一个标准化总线连接分立元件可能并没有什么那么大的好处，，并且硬件和软件工具的环境可能有很大的不同。 外围设备 嵌入式系统通过外围设备跟外界交流，如: , 串行通信接口(SCI):RS-232，RS-422，RS-485等。 , 同步串行通信接口:I2C，SPI，SSC和ESSI(增强型同步串行接口) , 通用串行总线(USB) , 多媒体卡(SD卡，闪存等) , 网络:以太网，LonWorks技术等。 , 现场总线:CAN总线，LIN总线，Profibus等。 , 计时器:PLL(S)，捕获/比较和时间处理单元 , 离散IO:又名通用输入/输出(GPIO) , 模拟到数字/数模转换器(ADC / DAC的) , 调试:JTAG接口的ISP，的ICSP的BDM端口，BITP，和DP9端口 工具 至于与其他软件，嵌入式系统设计师使用编译器，装配和调试，以开发嵌入式系 统软件。然而，他们也可以使用一些更具体的工具: , 的调试器或仿真器。 , 可以添加CRC校验程序的设备，所以嵌入式系统可以检查程序是有效的。 , 自定义的编译器和连接器可用于为特定的硬件改善优化。 , 嵌入式系统可能有自己特殊的语言或设计工具，或在现有的语言的基础上 添加增强功能，。 , 另一种方法是添加具有如DSPnano RTOS的DSP功能的实时操作系统或 嵌入式操作系统。 , 建模和代码生成工具往往是基于状态机。 软件工具有如下几个来源: , 在嵌入式市场运转的软件公司 , 从GNU软件开发工具移植过来 , 有时，当嵌入式处理器和一个普通的PC机处理器相近时，个人电脑的开 发工具可以被借鉴过来。 随着嵌入式系统复杂性的增长，更高级别的工具和操作系统迁移到商业将很有意义。例如，手机，个人数字助理和其它消费电脑经常需要购买，由个人而不是电子制造商提供重要的软件。在这些系统中，开放式的编程环境如Linux，NetBSD的，OSGi或嵌入式Java将变得很重要，以便于第三方软件供应商有一个更大的市场。 调试 嵌入式调试可在不同层次进行，这取决于提供的服务和设施。从最简单到最复杂的，他们大致可以分为以下几个方面 , 互动的居民调试，使用简单的shell提供的嵌入式操作系统 , 外部调试通过显示器或调试异构多核系统的服务器，使用记录或串口输出来跟踪操作。 , 电路调试器(ICD)，是通过JTAG或Nexus接口连接到微处理器的硬件设备。这使得可以从外部对微处理器进行控制操作，但通常被限制在调试处理器某个具体的功能。 , 电路仿真器(ICE)的取代模拟功能相当于一个微处理器，它可以提供对微处理器的有方面的全面控制。 , 一个完整的仿真器具有模拟硬件所有方面的能力，可以控制和修改硬件，并允许在一个普通的电脑上进行调试。 由于嵌入式系统往往由多种元素组成，调试的策略可能会有所不同。例如，调试以软件(或微处理器)为中心的嵌入式系统和调试依靠外围设备处理信息的嵌入式系统(DSP，FPGA协处理器)是不同的。今天越来越多的嵌入式系统使用超过一个处理器核心。多核心发展的一个普遍的问是正确的同步软件执行。在这种情况下，嵌入式系统的设计常常希望查看处理器内核之间的总线，这需要在数据流量层面的非常基础的调试检查，例如逻辑分析仪。