PDA intelligent terminal

PDA intelligent terminal  Products for medical and retail industries

    Generally speaking, intelligent terminal is a kind of embedded computer system equipment, so its architecture framework is consistent with the embedded system architecture; At the same time, as an application direction of the embedded system, the intelligent terminal has a clear application scenario setting. Therefore, its architecture is more clear and more granular than the ordinary embedded system, and it has some characteristics of its own.

  Intelligent terminal architecture

    Generally speaking, intelligent terminal is a kind of embedded computer system equipment, so its architecture framework is consistent with the embedded system architecture; At the same time, as an application direction of the embedded system, the intelligent terminal has a clear application scenario setting. Therefore, its architecture is more clear and more granular than the ordinary embedded system, and it has some characteristics of its own. The intelligent terminal architecture is divided into hardware architecture and software architecture.

    In terms of hardware, intelligent terminals generally adopt the classic computer architecture - the von Neumann architecture, which is composed of five major components, namely, the calculator (also called ALU), the controller (Controller), the memory (Memory), the input device and the output device, The arithmetic unit and controller constitute the core part of the computer - the Central Process Unit (CPU). Generally speaking, due to the increasing number of communication protocol stacks, multimedia and information processing are becoming more and more complex. Some general applications are often processed in independent processing units, thus forming a loosely coupled master slave multi computer system.

  Multi computer System Architecture of Intelligent System

   Each processing unit can be regarded as a separate computer system, running different programs. Each slave processing unit communicates with the application processing unit in a certain way, receives instructions from the application processing unit, performs corresponding operations, and returns results to the application processing unit. These specific processing unit chips often appear in the form of ASICs, but in fact, they are still computer systems on a chip. For example, the commonly used 2.5G baseband processing chip actually relies on the built-in ARM946 core execution program to implement the processing of GSM, GPRS and EDGE protocols.

  software structure

   As we know, computer software structure is divided into system software and application software. In the software structure of intelligent terminal, the system software mainly includes operating system and middleware. The function of the operating system is to manage all resources (including hardware and software) of the intelligent terminal, and it is also the core and cornerstone of the intelligent terminal system. The operating system is a huge management control program, which roughly includes five management functions: process and processor management, job management, storage management, device management, and file management. Common intelligent terminal operating systems include Linux, Windows CE, Symbian OS, iPhone OS, etc. Middleware generally includes function library and virtual machine, which makes the upper application independent of the lower hardware and operating system to some extent. The application software provides functions for users to use directly to meet their needs. From the level of providing functions, it can be understood that the operating system provides the underlying API, the middleware provides the high-level API, and the application program provides the interface to interact with users. In some software structures, applications can skip middleware and directly call some underlying APIs to use the underlying services provided by the operating system. Take the Android intelligent terminal software platform led by Google as an example, Linux is the operating system level. On the middleware level, it can also be subdivided into two layers, the lower layer is the function library and the Dalvik virtual machine, and the upper layer is the application framework, through which the services published by an application can be used by other applications. The top application uses the services provided by the bottom layer to ultimately provide users with application functions.

  Intelligent terminal hardware system

   The composition of intelligent terminal hardware system, abstractly speaking, takes the main processor core as the core, and divides the intelligent terminal hardware system into three levels to describe, namely, the main processor core, SoC level devices, and board level devices. The main processor core and SoC level devices are interconnected by on-chip bus, while the board level devices are generally connected to the system through SoC level devices.

   CPU and internal bus constitute a general computer processor core, which provides core computing and control functions. Considering the cost and reliability of the system, some commonly used devices and processor cores are generally integrated on a single chip, such as Flash controller, Mobile DDR controller, UART controller, memory card controller, LCD controller, etc. The board level equipment is generally connected with the main CPU through the communication interface, which is usually some processing units with independent functions (such as mobile communication processing units, GPS receivers) or interactive devices (such as LCD displays, keyboards, etc.).

   Board level devices are other devices that are not on the same chip as the processor core. It is called a board level device, mainly from the perspective of the relationship with the main processor core. From the perspective of architecture, it may also be a complete computer system. For example, the GPS receiver is also integrated with an ARM core to calculate the current position through the received satellite signals. Board level devices usually use data interfaces to connect with the main processor. For example, GPS receivers generally use UART interfaces to exchange data with the main processor. Board level devices are very rich, mainly including the following categories: memory chips, Flash chips, etc; Mobile communication processing section; The mobile communication processing part mainly provides mobile communication support, including baseband processing chip and RF chip. The baseband processing chip is used to synthesize the baseband signal to be transmitted or decode the received baseband signal. The baseband processing chip is generally a microprocessor+digital signal processor structure, which is connected to the main processor using UART interface. The RF chip is responsible for sending and receiving baseband signals.  Communication interfaces such as Bluetooth controller, infrared controller, WiFi network card, etc. Interaction; Such as speakers, microphones, keyboards, LCD displays, etc. Sensors; Such as camera, acceleration sensor, GPS, etc.

  Intelligent terminal processor and its technical characteristics

   Intelligent terminal processor is one of the core devices of intelligent terminal, and its function and efficiency have a great impact on the performance of the entire system. In the intelligent terminal hardware architecture described above, the intelligent terminal processor is equivalent to the collection of the core and SoC devices, and generally appears in the form of a single SoC chip. The basic requirements of intelligent terminals for processors are as follows:

   (1) High performance intelligent terminals are developing rapidly, and new applications are emerging one after another. Many applications require intelligent terminals to have high performance. Therefore, intelligent terminal processors are required to have high performance in order to provide users with complete functions and better experience.

   (2) The highly integrated intelligent terminal is very sensitive to size, so the processor is required to have a high degree of integration and be able to integrate more devices on a smaller size. This can not only control the whole terminal size, but also reduce the complexity of the design and improve the reliability of the system.

   (3) Most low-power intelligent terminals are battery powered, so the system power consumption is very sensitive. Therefore, the processor is required to have low power consumption. Some of the above three points complement each other. For example, high integration often means high performance; Some are contradictory, for example, the improvement of performance often leads to the increase of power consumption. This requires designers to consider the relationship between the three according to the application scenario and make reasonable design to achieve balance.