Application Prospect of FPGA in Embedded System

FPGA is a device that realizes various functions through logic combination and can perform almost any type of processing. For commonly used digital signal processing, some FPGAs also provide DSP modules to achieve acceleration; FPGA's parallel processing architecture is very suitable for image processing, Digital signal processing and other computationally intensive applications; when a chip cannot meet requirements, it can also provide higher processing power by using an FPGA chip with the same package and larger capacity, so that pin compatibility can be maintained. No need to modify the PCB; FPGA programmability allows design engineers to modify the design at any time, even after the product is deployed to correct design errors; FPGA can not only complete the MCU and DSP functions, but also based on Need to generate new functions, or allocate resource ratios among various functions, so that the same hardware circuit design can meet different application requirements; FPGA can also use off-the-shelf processor cores to directly generate soft processors, and in Run the operating system.

Since FPGAs implement their functions through logic combinations, their power consumption and cost are generally higher than those of MCUs and DSPs. A few years ago, FPGAs gave people the impression that prices were always high. In addition to a few industries such as communications, aerospace, military, and industrial, FPGAs are playing more of a role in prototype verification and development, and in the broader market such as consumer electronics. The situation has not been opened yet.

As Xilinx and Altera compete for new manufacturing processes, the price of the unit's gates is falling faster than ASICs, and prices are no longer an obstacle in many applications. Especially in some applications that require specific functions, designers cannot find devices on the market that meet the requirements. They must develop their own ASIC chips or use FPGAs to design. However, the costs and risks of developing ASICs are constantly increasing, even exceeding the future benefits. Using FPGAs has become a very practical choice.

Development Process Evolution

The development process of traditional embedded systems is generally to do a good hardware platform first, and then use the embedded system development tools to develop software on the hardware platform. The result of this is that the software developer must work after the hardware design is completed, or use various simulation tools to develop on the virtual hardware platform.

When developing with FPGA, the developer must first design the input (FPGA vendor-specific tools + language / schematic + IP CORE), then compile the simulation (FPGA vendor tools + simulation tools), and then board-level debugging (test board production + Logic analyzer) If you find a problem, recycle the above link.

This design model has many problems: poor design portability, lack of language and high cost of IP CORE, system simulation reliability and speed bottlenecks, the need to create a dedicated test board, the limitations of external test equipment, test board repeat production Lead to an extended development cycle.

In addition, from the schematic design, logic verification and simulation, circuit board design, development and debugging of embedded software, to the final comprehensive debugging, different tools from multiple vendors are used throughout the entire process. Not only do developers need to learn The use of software and techniques are just a matter of significant expenditure on capital investment. In addition, files are often called from one software source to another. Although each manufacturer claims that its software can guarantee compatibility, the increasingly complex functions and growing code of software make it difficult to completely assure compatibility.

Is there an integrated development environment that can complete the entire FPGA embedded system design? Yes, this is Altium Designer6.0. The predecessor of this software is Protel, which is widely known by electronic engineers. Until now, there are a large number of engineers using Protel for PCB board design. Altium Designer consists of three parts: Foundation is the front end of electronic product design, including schematic input, circuit simulation and verification, PCB and CAM document data browsing functions; Board Implementation can achieve traditional board-level circuit design, verification and CAM document editing functions; Embedded Intelligence Implementation is a digital circuit design based on large-scale programmable logic device (FPGA/CPLD), on-chip programmable embedded system software development and digital circuit real-time verification.

Altium Designer broadens the traditional boundaries of board design, integrates FPGA and PCB design, supports both schematic input and HDL hardware description input modes, and supports VHDL-based design simulation, mixed-signal circuit simulation, and layout pre/post signals Integrity analysis. The layout in the PCB layout design adopts a completely regular drive mode, and the gridless Situs topological logic autowiring function is used in the PCB layout; at the same time, the editing of the complete CAM output function is combined.

Altium Designer supports bi-directional synchronization of PCB and FPGA pins, provides comprehensive mixed-signal simulation, signal integrity analysis before and after routing, and provides interactive routing of high-density packages (such as BGA).

In the schematic part, Altium Designer's new features include: file management functions, multi-level, multi-channel principle design, automatic tagging of components, FPGA pin configuration import, PCB rule definition in the schematic environment, rich integration Library, improved editing, querying, and visualization.

The FPGA pin configuration import function allows pin-constraint files. The pin definitions can be directly derived from the FPGA device vendor's pin-constraints file, while providing support for pin name and electrical type definitions; no emphasis must be placed on the Altium Designer environment. Completion of integrated system design including FPGA internal logic circuit design.

Provides a complete rule-driven PCB design environment in the PCB section; supports high-speed design, has a mature post-route signal integrity analysis tool; supports differential pair routing; supports escape-fanout function of BGA packaged devices; Supports network optimization for any configurable pin-defining device; file import and export capabilities of Orc ad, PADS, AutoCAD, and other software; complete ODB++/Gerber CAM-system allows users to redesign existing designs to compensate for designs The difference between manufacturing and manufacturing. The PCB section also supports layout optimization, routing function optimization, 3D display of the PCB board, comprehensive FPGA coordination, and CAM output.

The embedded emulation software of Altium Desigenr is compatible with the XSPICE/PSPICE circuit simulation model. It can display the simulation results as waveforms, and can perform mixed circuit simulation and simulation waveform display, and supports multiple simulation models. In the signal integrity analysis section, anti-reflection and crosstalk analysis functions are provided,

In Altium Designer, users can use graphical methods to complete the entire design process. The system automatically invokes the tools provided by FPGA vendors for placement and routing. The centralized process control and monitoring capabilities in the design environment enable information to be fed back in time for interactive execution. Design and debugging.

Using "virtual instrument" components, engineers can connect "virtual instruments" to the design at the schematic level; after FPGA programming, they can be controlled from the outside; they can observe what happens in the FPGA in real time; use the JTAG boundary scan to verify the FPGA signal during debugging; Communicate with the Nexus protocol and virtual instrument and debug the design.

Altium Designer also provides a large number of common pre-verified IP Cores, support for the design of generic IP Cores, and support for third-party IP Cores. With the combination of the Nanoboard NB1 System Verification Board, real-time design is possible, enabling FPGA designs that are independent of the target device.

This kind of design method of Altium Company, the hardware, software and programmable hardware and other fields are all unified in a single development system, can completely control and synchronize the entire design process from the concept idea to the completion of the implementation.

The disadvantage of this integrated development process is that although it is very convenient and easy to use, all parts of the software cannot fully lead in performance and functionality, and are weaker than some professional ones in terms of verification, functional design, and PCB design. FPGA manufacturers' own software, Altium Designer may not be the best choice when it is necessary to perform very detailed optimizations for the device to achieve the best performance.

Locate different hardware development boards

Different from the software positioning, the current market positioning of numerous hardware development circuit boards is also different. The mainstream FPGA manufacturers have all launched their own development boards. In order to meet the needs of marketing and sales, they also cooperate with some large distributors to launch development boards, making it easier to use the advantages of distributors in terms of price and channels.

Xilinx's main distributor, Avnet, has developed many FPGA development boards that are more feature-rich and more flexible in pricing and promotion. For example, Avnet introduced the Virtex-4 FX PCI Express development kit and the Virtex-5 LX development kit.

Finding an FPGA development board that exactly meets the needs of the developer is very difficult, and adding a daughter board to the board is a good idea. Avnet's EXP expansion standard allows designers to add multiple functions through the daughter card during prototyping to meet the different requirements of the FPGA development board and is provided free to the design engineer to customize the basic board and expansion module. The benefits of using the EXP module are low cost, high flexibility, and ease of prototype creation. Structurally, the half-length EXP module provides 84 user I/Os, 32 single-ended signals, 22 differential signals, single-ended clock inputs and outputs, differential clock inputs and outputs, and the highest frequencies of single-ended and differential signals, respectively It is 200MHz and 700MHz.

The EXP modules provided by Avnet include: Video Preprocessing Modules, High-Speed ​​ADC Modules, High-Speed ​​DAC Modules, and Analog Devices' EXP Adapter Modules. It is available in both full-length (126mm x 80mm) and half-length (108mm x 80mm) sizes, using Samtec's high-performance QTE/QSE connectors.

The video preprocessing module's input is compatible with DVI, VGA, S-Video, and the output supports DVI, VGA, LCD, with image sensor, audio input and output. The high-speed ADC EXP module uses TI's 12-bit, 50MS/s ADC with a 14-bit LVDS interface and supports dual channels with two cards. The high-speed DAC module uses TI's dual-channel, 16-bit resolution, sampling rate of 1GS/s, DAC with 16-bit LVDS interface. There are also EXP adapter modules that support ADI devices that can be easily connected to more than 90 ADC evaluation boards, support LVDS and parallel interface evaluation boards, and connect to Virtex-4, Virtex-5, and Spartan-DSP substrates.

Altium's NanoBoard development board supports a wider range of FPGA models, including Xilinx, Altera, Actel, etc., and FPGAs form a reconfigurable system design verification platform; NanoBoard communicates with user PCs via a print cable interface, supporting Hardware design downloads and Live design verification features. The NanoBoard also supports pluggable FPGA daughter boards that can be used to debug different FPGAs by changing daughter boards.

NanoBoard's on-board resources include: CAN bus interface, serial port, VGA interface, display chain input and output, external memory, I2C interface, connection to user development board interface, socket to connect FPGA daughter board, system clock, JTAG interface, PS2 keyboard And mouse mouse interface, multi-user I/O interface. The user can complete the development and verification of the entire system on a single board. By changing the daughter card, different manufacturers of different devices can be tried to find the most cost-effective device without having to purchase the development board repeatedly.

As the FPGA manufacturing process progresses toward 65nm, 45nm, and more advanced processes, the device cost of FPGAs will become lower and lower. In order to achieve a differentiated competitive advantage, system vendors must develop unique product features, but the use of ASSPs and ASICs can only provide fixed limited functionality, while the huge cost and risk of developing ASICs make ASICs only a few large companies. select. FPGAs with declining costs have become the best choice for most system vendors, but the lack of synchronization between software and hardware in the traditional design flow, the need to cross-use multiple software, and the limited support of the hardware development board may become an obstacle to more adoption of FPGAs. The problem. Altium’s Altium Designer is the industry’s first development tool to provide an integrated design environment. If more manufacturers are involved in the development of similar software tools and continue to improve ease of use and performance, then this design concept can be truly promoted. A broader application area.

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