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Embedded System Design And History

Embedded System Design And History. Outline. Introduction History Embedded System Design Embedded Microprocessor Embedded Operating System Embedded Linux Distributions Embedded Application. What is Embedded System?.

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Embedded System Design And History

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  1. Embedded System Design And History

  2. Outline • Introduction • History • Embedded System Design • Embedded Microprocessor • Embedded Operating System • Embedded Linux Distributions • Embedded Application

  3. What is Embedded System? • An embedded system is a special-purpose system in which the computer is completely encapsulated by the device it controls. • An embedded system performs pre-defined tasks, usually with very specific requirements. • Mobile phones, MP3 Players, Digital Cameras are very common embedded systems in our life.

  4. What is Embedded System? • Since the system is dedicated to a specific task, design engineers can optimize it and reduce the size and cost of the product. • Power Constrain, Performance requirements. • Embedded systems are often mass-produced, so the cost savings may be multiplied by millions of items.

  5. Outline • Introduction • History • Embedded System Design • Embedded Microprocessor • Embedded Operating System • Embedded Linux Distributions • Embedded Application

  6. History • Apollo Guidance Computer (AGC), 1963 [1] • The first recognizably modern embedded system. • Developed by Charles Stark Draper at the MIT Instrumentation Laboratory . • Used in real-time by astronaut pilots to collect and provide flight information. • Automatically control all of the navigational functions of the Apollo spacecraft. • The Apollo flight computer was the first to use integrated circuits (ICs). • The computer's RAM was magnetic core memory (4K words) and ROM was implemented as core rope memory (32K words). Source: The Computer History Museum

  7. History • D-17 Guidance Computer, 1961 ~ 1966 [1] • The first mass-produced embedded system developed for Minuteman missile. • Built from discrete transistor logic and had a hard disk for main memory. • When the Minuteman II went into production in 1966, the D-17 was replaced with a new computer that was the first high-volume use of integrated circuits. • This program alone reduced prices on quad NAND gate ICs from $1000/each to $3/each, permitting their use in commercial products.

  8. History • Intel 4004, [1] • The first microprocessor. • Which found its way into calculators and other small systems. • Required external memory and support chips. • 8-bit Microprocessor, 1971-1974 • 8008, 8080, 8085, 6800, 6502, Z-80, Ti, NS • Hundred if not thousand vendors rushed into this market. • The 6502 was used by Apple Co. to design Apple-II, which sparked the Personal computer era.

  9. History • 16-bit CPU • 8088, 8086, 80286 Z-800. 68000 • About 20 companies had released their products. • Why did the 16-bit CPU not make any significant impact in the market? • IBM PC Era began from 1979 • 8088 was used in PC and PC/XT, 80286 was used in the PC/AT. • This adoption of Intel CPU plus the OS supplied by Microsoft created two biggest PC Giants (Monsters) rule the world up to this day. • 80286 is used in IBM PS/2 personal computer system . • M$ intentional persuaded the IBM to use assembly to implement the OS/2 so that caused a long delay of the OS/2-286 release. During that time, Bill Gate secretly develops the Windows to emulate the Mac’s OS. • Single chip microcontroller (8051 MCU) series which was developed by Intel in 1980 for use in embedded systems .

  10. History • 32-bit CPU • 68020, 80386, NS32032, Z8000, Japan TRON CPU . • Only a handful manufacturer would be able to reach the 32-bit CPU market. Why ? • The era of the RISC • the era RISC Reduced Instruction Set Computer comes. (RISC vs. CISC) But the battle turned out to be the CISC(x86)'s big victory. • The code density for RISC is poor compared to the CISC. • The large installed X86 PC software base is a big hurdle to the RISC machines to overcome.

  11. History • Simple history of RISC • Even the RISC idea (around 1980) was rebutted by the computer architects during its early development. • For at that time, most computer architects tried to enhance the performance of CPU by adding more complex instructions . • RISC is simply against the intuition. Why RISC prevails? • X86 vs. RISC ... This is a big question!

  12. History • Notable RISC CPUs • MIPS, PPC, M88000, PA-RISC, DEC-Alpha, Clipper, ARM • Architecture Design • Instruction, Register set, memory model, pipelined architecture, Superscalar, simultaneous multithreading, multi-core. • Does RISC really reduce the instruction set? • So what is the key to the 32-bit RISC? A Big design Team is needed.

  13. History • Architecture is far too complex for a small company to handle. Compiler tool chain support, OS, middle ware, development kit... • (FPAG + CPU==> NIOS-II, Microblaze, ARM and PPC, from Altera, Xilinx...) • Their costs range from USD$3-4 to 30-40 or more. Power problem... The X86 CPU reached 4 GHz around 2001. But no fast CPU was made to the market.

  14. History • RISC vs X86 • In the performance with application base game, the RICS failed miserably to the Intel’s X86 architecture. • So the RISC company had to find the alternative market and focused on the embedded system. • The tide has been changing now, the RISC power player ARM strikes back. In low-power application the X86 is no match to the ARM.

  15. ARM history ARM0: Acorn Computers Ltd used 6502 (which powered Apple-II then) to design BBC Micro computer. • ARM1 ARM 2: (Inspired by Berkley RISC project) • The official Acorn RISC Machine project started in October 1983. • VLSI Technology, Inc was chosen as silicon partner. • VLSI produced the first ARM silicon on 26 April 1985 – it worked the first time and came to be termed ARM1 by April 1985. • The first "real" production systems named ARM2 were available the following year.

  16. ARM History • ARM Family ARM Architecture ARM Core Feature Cache (I/D), MMU Typical MIPS @ MHz • ARM1 ARMv1 ARM1 First implementation None • ARM2 ARMv2 ARM2 ARMv2 added the MUL (multiply) instruction None 4 MIPS @ 8 MHz • 0.33 DMIPS/MHz • ARMv2a ARM250 Integrated MEMC (MMU), Graphics and IO processor. ARMv2a added the SWP and SWPB (swap) instructions. None, MEMC1a 7 MIPS @ 12 MHz • ARM3 ARMv2a ARM3 First integrated memory cache. 4 KB unified 12 MIPS @ 25 MHz • 0.50 DMIPS/MHz • ARM6 ARMv3 ARM60 ARMv3 first to support 32-bit memory address space (previously 26-bit) None 10 MIPS @ 12 MHz • ARM7TDMI ARMv4T ARM7TDMI(-S) 3-stage pipeline, Thumb none 15 MIPS @ 16.8 MHz • 63 DMIPS @ 70 MHz • ARM9TDMI ARMv4T ARM9TDMI 5-stage pipeline, Thumb none

  17. ARM Key Architecture The ARM architecture includes the following RISC features: • Load/store architecture. • No support for misaligned memory accesses (now supported in ARMv6 cores, with some exceptions related to load/store multiple word instructions). • Uniform 16 × 32-bit register file. • Fixed instruction width of 32 bits to ease decoding and pipelining, at the cost of decreased code density. Later, the Thumb instruction set increased code density. Now Thumb-2 ISA • Mostly single-cycle execution.

  18. ARM architecture To compensate for the simpler design, compared with contemporary processors like the Intel 80286 and Motorola 68020, some additional design features were used: • Conditional execution of most instructions, reducing branch overhead and compensating for the lack of a branch predictor. • Arithmetic instructions alter condition codes only when desired. • 32-bit barrel shifter which can be used without performance penalty with most arithmetic instructions and address calculations. • Powerful indexed addressing modes. • A link register for fast leaf function calls. • Simple, but fast, 2-priority-level interrupt subsystem with banked register banks.

  19. ARM Cortex • Application Profile-A8, A9, A15, A7 • Real-time Profile Cortex-R4 • MCU profile M3, M4 (Low power of M : NXP's Cortext-M3 0.05mW/MHz, M4 0.06mW/Mhz. NXP-LPC430 ==> M0 + M4 running at 150MHz consumes only 9mW)

  20. A glance of Cortex A8 • Key features of the Cortex-A8 core are: • * Frequency from 600 MHz to 1 GHz and above • * Superscalar dual-issue microarchitecture 13-stage superscalar pipeline • * NEON SIMD instruction set extension (optional) • * VFPv3 Floating Point Unit (optional) • * Thumb-2 instruction set encoding • * Jazelle RCT • * Advanced branch prediction unit with >95% accuracy • * Integrated level 2 Cache (0-4 MB) • * 2.0 DMIPS / MHz

  21. VFP and (for floating point) • NEON (SIMD) Instruction Set. (For Multimedia applications)

  22. Amazon Kindle: FreeScale i.MX508, Cortex-A8 • Xilinx's Zynq : Dual core A9 MPcore(hard core CPU) + FPGA (235K--30K Logic cells), USB, Gbps ethernet, 10.315 Gbps serial

  23. ARM Entering the Server Market • SAN JOSE, Calif. -- Startup Calxeda (Austin) has released a few details about its unannounced ARM-based processor aimed at low power servers. • Calxeda's initial reference design will be based on a quad-core Cortex A9 SoC that consumes 5W including associated DRAM. The chip includes a fabric that acts as an interconnect to other processors, enabling OEMs to pack as many as 120 SoCs in a 2U-sized chassis. • (Rackmount 19 inches wide 1U 1.75 inches)

  24. ARM Entering the Server Market • SAN JOSE, Calif. – Marvell will try to thrust ARM into servers and networking gear with a 1.6 GHz quad-core Cortex A9 chip debuting at the ARM Technology Conference. The Armada XP aims at a broad range of systems from low power Web servers for business to network-attached storage and media servers for the digital home. • The Armada XP delivers up to 16,600 Dhrystone MIPS at 10W. It includes up to 2 Mbytes L2 cache and supports a 64-bit interface to DDR2/3 memory running at up to 800 MHz.

  25. Outline • Introduction • History • Embedded System Design • Embedded Microprocessor • Embedded Operating System • Embedded Linux Distributions • Embedded Application

  26. Embedded System Design • Components of embedded system: • Hardware • Processor, memory, ASIC, controllers, peripherals… • Firmware/software • Boot loader, embedded OS, device drivers, applications… • Design and Development Skills: • HDL: Verilog, VHDL … • I/O, analog and digital interfacing, peripherals … • Development kits: Compiler, linker … • Firmware design: Assembly and Low-level C language • Device driver design • Embedded operating system design or porting • System programming: System calls, IPC, Socket … • Application software design: JAVA, C++ …

  27. Embedded System Design • Example: Digital camera hardware block diagram Processor Core DSP LCD Controller Image De/Encoder SPI USB Controller Memory Interface PIO Interface ADC RTC SRAM SDRAM Flash SoC

  28. Embedded System Design • Example: Digital camera firmware/software Image Capturer Image Processing System Configure File Manager GUI Several Tasks Embedded OS Device drivers: LCD, Sensor, SD Card … Low level initializing code (Boot loader)

  29. Embedded System Design Issues • Cost and Performance • Lowering the cost affects the speed of embedded system. • Most often speed issue doesn’t matter and one achieves the task at lower cost. • Simplifying the hardware allows cost reduction. • Specifications and User Constraints • Specifications define that what task is to be achieved. • The constraints help the designer to select appropriate hardware and software setup to develop an embedded system. The selection of an embedded system depends upon the requirement specifications.

  30. CPU Architecture ARM or MIPS or … ? Storage Size and Speed SDRAM or DDR ? RAM, ROM, Flash memory size ? Interfaces PIO or RS232 or …? Touch screen or keypad ? Development kits GNU tools or others ? Embedded OS Real-time or not? Kernel size ? Multi-task supported ? Easy to port ? Embedded Applications Implement with C, C++ or JAVA … ? GUI: Microwindows or MiniGUI or … ? Embedded System Design Issues • Selection of hardware and software of an embedded system

  31. Embedded Hardware Design • Hardware Design Technology • System on a Chip (SoC) • Integrating all components of a computer or other electronic system into a single chip. • System on a Programmable Chip (SoPC) • SoPC is a family of mixed-signal arrays made by Cypress Semiconductor, featuring a microcontroller and integrated analog and digital peripherals.

  32. Embedded Hardware Design Figure: SoC Design Flow (Top-half) Source: Wikipedia, the free encyclopedia [1]

  33. Embedded Hardware Design Figure: SoC Design Flow (Bottom-half) Source: Wikipedia, the free encyclopedia [1]

  34. Embedded Hardware Design • Hardware Description Language (HDL) • VHDL and Verilog • The two most widely-used and well-supported HDL varieties used in industry. • Others include • ABEL (Advanced Boolean Expression Language) • AHDL (Altera HDL, a proprietary language from Altera) • JHDL (based on Java) • Lava (based on Haskell) • MyHDL (based on Python) • PALASM • RHDL (based on Ruby)

  35. Embedded Hardware Design • Design, Synthesis Tools • Altera • Max-plus II, Quartus II, SoPC Builder • Xilinx • ISE • Synplicity • Synplify • Simulation Tools • Model Technology • ModelSim

  36. Embedded Software Design • Software Architecture Definition • This is the first stage of embedded software design. • Here the software team understands the system that is being designed. • The team also reviews at the proposed hardware architecture and develops a very basic software architecture. • This architecture definition will be further refined in co-design. • The complexity of embedded software depends on the application of your system.

  37. Embedded Software Design • Common types of embedded software • Single-tasking or multi-tasking • Only one task needs to be performed at one period of time  Single-tasking • Several tasks need to be performed at one period of time  Multi-tasking A finished B finished Task A Task B time A finished Task A Task A C finished B finished Task B Task B Task C Task C time

  38. Embedded Software Design • Single-tasking example • ATM • Multi-tasking example • Multimedia phone Withdraw money Transfer accounts Show account info time Play MP3 … … JAVA Game time

  39. Embedded Software Design • Non-real-time system or real-time system • Non-real-time system • A non-real-time system is one for which there is no deadline, even if fast response or high performance is desired or even preferred. • Real-time system • Hardware and software systems which are subject to a "real-time constraint" — i.e. operational deadlines from event to system response. • A real-time system may be one where its application can be considered (within context) to be mission critical.

  40. Embedded Software Design • Real-time system example • Anti-lock Brakes System (ABS) • A system on motor vehicles which prevents the wheels from locking while braking. • Real-time constraint • The short time in which the brakes must be released to prevent the wheel from locking. • Real-time computations are not completed in the time-period after the event before the deadline relative to the event  have failed.

  41. Embedded Software Design • Hard and Soft real-time system • Hard real-time system • The correctness of an operation depends not only upon the logical correctness of the operation but also upon the time at which it is performed. • Hard real-time systems are typically found interacting at a low level with physical hardware, in embedded systems. • Example: Car Engine Control System • A delayed signal may cause engine failure or damage. • Other examples • Nuclear power stations • Car airbags

  42. Embedded Software Design • Soft real-time system • Soft real-time systems are typically those used where there is some issue of concurrent access and the need to keep a number of connected systems up to date with changing situations. • Example1: The flight plans management system • The software that maintains and updates the flight plans for commercial airliners. • These can operate to a latency of seconds. • Example2: Live audio-video systems • Violation of constraints results in degraded quality, but the system can continue to operate.

  43. Embedded Software Design • It is important to note that • Hard versus soft real-time does not necessarily relate to the length of time available. • A processor does not turn on cooling within 15 minutes  machine may overheat (hard real-time). • A network interface card is not read within a fraction of a second  may lose buffered data but the data can be resent over the network if needed (soft real-time). • Real-time ≠ high performance • For Anti-lock Brakes System • Has been designed to meet its required deadlines. • No further performance gains are necessary.

  44. Embedded Software Design • Development Kits • GNU Tools • Free software, easy to get for developing.(Free as in Freedom) • Abundant in documents, manuals and lots of developing societies, easy to learn. • Fully support the GNU-based software such as Linux, Linux-based software, simplify the porting process. • Multiple platform supported, such as x86, ARM, MIPS, NIOS, PowerPC … • Operate in command line mode. • Basic tools • C/C++ Compiler: gcc, g++ • Assembler: as • Linker: ld • Debugger: gdb • Others: objcopy, objdump, nm, ar, strip, ranlib …

  45. Embedded Software Design • Integrated Development Environment (By ARM’s example) • ARM Software Development Tools (ARM SDT) • Provided by ARM company. • Basic tools • C/C++/THUMB Compiler: armcc, tcc • Assembler: armasm • Linker: armlink • Debugger: armsd • ADS is the newer version of SDT. • ARM Developer Suite (ADS) [2] • An Integrated Development Environment for Windows, Linux and Solaris. • GUI development environment and debugger. • Support for families of processors including ARM7, ARM9, ARM9E, ARM10, StrongARM and Intel XScale. • Real-time Debug and Trace support. • On-line documentation.

  46. Embedded Software Design • Software Porting • Porting is often a necessary process of designing a complex embedded system. • What kind of software can we port from existing software ? • Boot loader  U-Boot, LILO … • Embedded OS  uClinux, uCOS-II … • Applications  mplayer, microwindows • Software selection issues for porting • Software complexity ? • Software is well-ported ? • What is the development tool that the software based on ?

  47. Embedded Software Design • Example: U-Boot (The Universal Boot Loader) • A GPL'ed cross-platform boot loader shepherded by project leader Wolfgang Denk. • Supports for hundreds of embedded boards and a wide variety of CPUs including PowerPC, ARM, MIPS, NIOS, and x86 ...etc. • Easily configure to strike the right balance between a rich feature set and a small binary footprint. • Allowing you to focus on the core of your embedded application. • Can easily add support for new hardware or add a special feature in U-Boot.

  48. Hardware/Software Co-Design [3] • Current methods for designing embedded systems require to specify and design hardware and software separately. • Designers often strive to make everything fit in software, and off-load only some parts of the design to hardware to meet timing constraints. • The problems with these design methods are: • Lack of a unified hardware-software representation • Leads to difficulties in verifying the entire system. • A priori definition of partitions • Leads to sub-optimal designs. • Lack of a well-defined design flow • Makes specification revision difficult, and directly impacts time-to-market.

  49. Hardware/Software Co-Design • Hardware/Software co-design can be defined as the cooperative design of hardware and software. • Co-design research deals with the problem of designing heterogeneous systems. • One of the goals of co-design is to shorten the time-to-market while reducing the design effort and costs of the designed products.

  50. Hardware/Software Co-Design Figure: The design flow of the general co-design Source: [4]

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