CS 244 Introduction to Embedded Systems and Ubiquitous

CS 244 -Introduction to Embedded Systems and Ubiquitous Computing Instructor: Eli Bozorgzadeh Computer Science Department UC Irvine Winter 2012

Introduction to Embedded Systems n Suggested Textbooks: q q q n Embedded System Design, by F. Vahid and Givargis, Wiley, 2002 Embedded System Design, by P. Marwedel, Kluwer Academic, 2003 Embedded System Design, by Gajski, Abdi, and et. al. , Springer, 2008 Other sources q q Lecture notes handouts Winter 2010 - CS 244 2

Course outline n Lectures q n n Mon-Wed-Fri: 3: 00 -3: 50 p. m. Office hours: Friday 10 -11 a. m. Grading policy: q q 25%: reading assignments + quizzes (2 -3) 25%: homework and project assignments (2 -3) 25%: literature survey (group of 2 -3) 25%: Final Winter 2010 - CS 244 3

Outline n n What are embedded systems? Embedded System Components q n n Hardware/software Embedded System applications Model, languages and tools Hardware/software co-design and synthesis Real time Operating systems Copyrighted Material adapted from slides by Peter Marwedel, Frank Vahid, Tony Givargis, Dan Gajski, and Nikil Dutt Winter 2010 - CS 244 4

What’s an Embedded System? n Embedded systems = q n Two types of computing q q n Desktop – produced millions/year Embedded – billions/year Non-Embedded Systems q n information processing systems embedded into a larger product PCs, servers, and notebooks The future of computing! q Automobiles, entertainment, communication, aviation, handheld devices, military and medical equipments. 5

Embedded Systems n Devices other than desktop PCs, servers, and notebooks q q n n n Electricity running through Perform something intelligent Hardware/software which form a component of a larger system, but are concealed from user Computers camouflaged as non-computers The future of computing! 6 6

An Example Embedded System Digital Camera Block Diagram 7

ES: Simplified Block Diagram actuators 8

Course Outline Hardware Components Concept Specification Hardware HW/SW Partitioning Estimation Exploration Software Components gn i s De ) t, … u ayo L , sis e nth y S ( De sig n (C om pil ati on , …) Software Validation and Evaluation (area, power, performance, …) 9

Components of Embedded n. Systems Analog Components q n Digital Components q q n n Sensors, Actuators, Controllers, … Processor, Coprocessors Memories Controllers, Buses Application Specific Integrated Circuits (ASIC) Hardware Converters – A 2 D, D 2 A, … Software q q Application Programs Exception Handlers Software 10

Hardware Components

Hardware Components of Embedded Systems- an example Memory Controllers Interface Software (Application Programs) Coprocessors Processor ASIC Converters Analog Digital 12 Analog

Processors n What is a processor? q q n General-purpose (GP) processors: q q q n Artifact that computes (runs algorithms) Controller and data-path Variety of computation tasks Functional flexibility and low cost at high volumes (maybe) Slow and power hungry Single-purpose (SP) processors (or ASIC) q q q One particular computation task Fast and power efficient Functional inflexibility and high cost at low volumes (maybe) 13 13

GP/SP Processor Architecture Status Data Input Data-Path Data Output Controller Control 14 14

General-purpose processors n Programmable device used in a variety of applications q n q Program memory General datapath with large register file and general ALU User benefits q q n Datapath Control logic and State register Register file Features q n Also known as “microprocessor” Controller Low time-to-market and NRE costs High flexibility IR PC Program memory General ALU Data memory Assembly code for: total = 0 for i =1 to … Examples q Pentium, Athlon, Power. PC 15

Application-specific IS processors (ASIPs) Programmable processor optimized for a n n particular class of applications having common characteristics q Compromise between general-purpose and ASIC (custom hardware) Features q Program memory q Optimized datapath q Special functional units Benefits q Some flexibility, good performance, size and power Examples q DSPs, Video Signal Processors, Network Processors, . . Controller Datapath Control logic and State register Registers IR PC Program memory Custom ALU Data memory Assembly code for: total = 0 for i =1 to … 16

Application-Specific ICs (ASICs) n Digital circuit designed to execute exactly one program q n Features q q n coprocessor, hardware accelerator Contains only the components needed to execute a single program No program memory Controller Datapath Control logic index total State register + Data memory Benefits q q q Fast Low power Small size 17

Application Specific Circuits (ASIC) n. Custom-designed circuits necessary if ultimate speed or energy efficiency is the goal and large numbers can be sold. n. Approach suffers from long design times and high costs. 18

GP vs. SP Processors GP: n Programmable controller q q n n Control logic is stored in memory Fetch/decode overhead Highly general data-path q ASIC: q q n Typical bit-width (8, 16, 32, 64) Complete set of arithmetic/logic units Large set of registers High NRE/sale-volume Hardwired controller Highly tuned data-path q q q n No need for program memory and cache No fetch/decode overhead Custom bit-width Custom arithmetic/logic units Custom set of registers Low NRE/sale-volume 19 19

Storage n What is a memory? q q n Write-ability q n ability of memory to hold stored bits after they are written Many different types of memories q n Manner and speed a memory can be written Storage-permanence q n Artifact that stores bits Storage fabric and access logic Flash, SRAM, DRAM, etc. Common to compose memories 20 20

Write-ability n Ranges of write ability q High end n n q Middle range n n q Processor writes to memory, but slower E. g. , FLASH, EEPROM Lower range n n q Processor writes to memory simply and quickly E. g. , RAM Special equipment, “programmer”, must be used to write to memory E. g. , EPROM, OTP ROM Low end n n Bits stored only during fabrication E. g. , Mask-programmed ROM 21 21

Storage-permanence n Range of storage permanence q High end n n q Middle range n n q Holds bits days/months/years after memory’s power source turned off E. g. , NVRAM Lower range n n q Essentially never loses bits E. g. , mask-programmed ROM Holds bits as long as power supplied to memory E. g. , SRAM Low end n n Begins to lose bits almost immediately after written E. g. , DRAM 22 22

Storage-permanence Memory Types Mask-programmed ROM In-system programmable Ideal OTP ROM EPROM EEPROM Flash NVRAM Nonvolatile SRAM/DRAM Write-ability 23 23

Communication n What is a bus? q q n An artifact that transfers bits Wires, air, or fiber and interface logic Associated with a bus, we have: q Connectivity scheme n n n q Protocol n n n q Serial Communication Parallel Communication Wireless Communication Ports Timing Diagrams Read and write cycles Arbitration scheme, error detection/correction, DMA, etc. 24 24

Serial Communication n A single wire used for data transfer One or more additional wires used for control (but, some protocols may not use additional control wires) Higher throughput for long distance communication q n n Often across processing node Lower cost in terms of wires (cable) E. g. , USB, Ethernet, RS 232, I 2 C, etc. 25 25

Parallel Communication n Multiple buses used for data transfer One or more additional wires used for control Higher throughput for short distance communication q q n n Data misalignment problem Often used within a processing node Higher cost in terms of wires (cable) E. g. , ISA, AMBA, PCI, etc. 26 26

Wireless Communication n Infrared (IR) q Electronic wave frequencies just below visible light spectrum Diode emits infrared light to generate signal Infrared transistor detects signal, conducts when exposed to infrared light Cheap to build q Need line of sight, limited range q q q n Radio frequency (RF) q q q Electromagnetic wave frequencies in radio spectrum Analog circuitry and antenna needed on both sides of transmission Line of sight not needed, transmitter power determines range 27 27

Peripherals n n Perform specific computation task Custom single-purpose processors n n Designed by us for a unique task Standard single-purpose processors n n “Off-the-shelf” pre-designed for a common task 28 28

Timers n Timers: measure time intervals q q q n To generate timed output events To measure input events Top: max count reached Basic timer Clk 16 -bit up counter 16 Cnt Top Reset Range and resolution 29 29

Counters n Counter: like a timer, but counts pulses on a general input signal rather than clock q q e. g. , count cars passing over a sensor Can often configure device as either a timer or counter Timer/counter Clk 2 x 1 mux 16 -bit up counter Cnt_in 16 Cnt Top Reset Mode 30 30

Watchdog Timer n n Must reset timer every X time unit, else timer generates a signal Common use: detect failure, self-reset 31 31

UART n UART: Universal Asynchronous Receiver Transmitter q q n n n Takes parallel data and transmits serially Receives serial data and converts to parallel Parity: extra bit for simple error checking Start bit, stop bit Baud rate q q Signal changes per second Bit rate, sometimes different 32 32

Pulse Width Modulator (PWM) n n Generates pulses with specific high/low times Duty cycle: % time high q n Square wave: 50% duty cycle Common use: control average voltage to electric device q q Simpler than DC-DC converter or digitalanalog converter DC motor speed, dimmer lights 33 33

LCD n n n Liquid Crystal Display N rows by M columns Controller build into the LCD module Simple microprocessor interface using ports Software controlled 34 34

Keypad N 1 N 2 N 3 N 4 k_pressed M 1 M 2 M 3 M 4 4 key_code keypad controller N=4, M=4 35 35

Stepper Motor Controller n Stepper motor: rotates fixed number of degrees when given a “step” signal q n n In contrast, DC motor just rotates when power applied, coasts to stop Rotation achieved by applying specific voltage sequence to coils Controller greatly simplifies this 36 36

5. 0 V 4. 5 V 4. 0 V 3. 5 V 3. 0 V 2. 5 V 2. 0 V 1. 5 V 1. 0 V 0. 5 V 0 V 1111 1110 1101 1100 1011 1010 1001 1000 0111 0110 0101 0100 0011 0010 0001 0000 proportionality 4 4 3 3 analog output (V) Vmax = 7. 5 V 7. 0 V 6. 5 V 6. 0 V 5. 5 V analog input (V) Analog-to-Digital Converter 2 1 t 2 0100 t 3 t 4 time 1000 0110 0101 Digital output Analog to Digital (A/D) 2 1 t 1 0100 t 2 t 3 1000 0110 Digital input t 4 time 0101 Digital to Analog (D/A) 37 37

Summary n Hardware: Information Processing q q Processors Memories Communication Peripherals 38