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CSE 91 Fall 2009 Embedded Systems

CSE 91 Fall 2009 Embedded Systems. Rajesh K. Gupta Computer Science and Engineering University of California, San Diego. Topics We Will Discuss. What are embedded systems? How do computers ‘interface’? What has that got to do with computers and ‘chips’?

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CSE 91 Fall 2009 Embedded Systems

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  1. CSE 91 Fall 2009Embedded Systems Rajesh K. Gupta Computer Science and Engineering University of California, San Diego. 2009 R. Gupta, UCSD

  2. Topics We Will Discuss • What are embedded systems? • How do computers ‘interface’? • What has that got to do with computers and ‘chips’? • Hands-on Exercise: Do It Yourself Computing • How do we connect different components? • How do we program embedded systems? Keywords: Embedded Computer Programmable Systems Systems on Chip PSOC I2C, Serial, USB, ASCII ISA 2009 R. Gupta, UCSD

  3. "Embedded Everywhere" 2009 R. Gupta, UCSD

  4. The Computing Experience • The Computer Center • Mainframe computing • The Personal Computer • Desktop, laptop, palm top computing • The Ubiquitous Embedded Computer • Mobile, purpose-built. 2009 R. Gupta, UCSD

  5. CPU Memory Address Controller DataPath control enables selects R/W Data data conditions Hardware Architecture & Organization • Computer Architecture is how a builder/user sees it • How do you see your house? This building? • Instruction Set Architecture (ISA), Memory System Architecture • Computer Organization refers to the structure of a computer: 2009 R. Gupta, UCSD

  6. Application Compiler Assembler Micro-operations Hardware Software ‘Architecture’ Embedded Software And Configuration 2009 R. Gupta, UCSD

  7. A Personal Computer (PC) • Uses commodity components and standard interfaces to build the machine • Choose different components for performance, capacity, cost • Faster hard drive, processor, memory, interfaces 2009 R. Gupta, UCSD

  8. PC Components • Case: • desktop, minitower, mid case, mid tower, full tower, large tower • include a power supply (typically 200 watts) • CPU and CPU fan • sold as a chip • Motherboard • single-board computer • contains place holders for CPU and Memories • Memory modules • Interfaces • Video (card and monitor) • Others: (I/O card) “Floppy, CD-ROM, Keyboard, Hard drive, Sound card, Speakers, Modem, Tape/zip , Mouse” 2009 R. Gupta, UCSD

  9. 168-pin SDRAM The Stuff at Fry’s 184-pin DDR-SDRAM 2009 R. Gupta, UCSD

  10. Not at Fry’s Yet! Mani Srivastava, UCLA 2009 R. Gupta, UCSD

  11. CPU MEM BUS Personal Computing • “Low cost and general purpose” CPU DATA INST BUS 2009 R. Gupta, UCSD

  12. CPU MEM BUS Devices Devices Devices Computer Organization 1 3 2 4 Drives Input devices Output devices Networking Interface 2009 R. Gupta, UCSD

  13. CPU MEM BUS Devices Devices Devices Memory 2-3 GHz 50 ns SIMM PC2-5300 667 MHz DIMM 2009 R. Gupta, UCSD

  14. Controller DataPath control enables selects data conditions select CPU – Memory Interaction Clock 200 ns CPU Memory Address clock R/W addr VALID Data 500 ns • CPU controlled by a clock pulse. • Memory is controlled by R/W control signals. • CPU must synchronize its memory read, write operations with respect to its internal clock. • Example: 5 MHz clock, 500 ns access time. R/W’ data VALID WRITE CYCLE 2009 R. Gupta, UCSD

  15. A Processor’s Interfaces 2009 R. Gupta, UCSD • Two basic types • Communicate ‘via’ memory • Sender writes to a memory location • Receiver reads from that memory location • Communicate directly • Sender and receivers connected by ‘ports’ • How do we measure goodness of an interface? • Maximum data-rate of transfer? Bits or bytes per second?

  16. What is this connector? A “Serial” Port 9-pin RS232C: DE-9 2009 R. Gupta, UCSD

  17. Then What Are These? 2009 R. Gupta, UCSD

  18. From RS232c to USB • “D-Sub” connectors • A: 15 pin • B: 25 pin • C: 37 pin • D: 50 pin • E: 9 pin • RS232 was DB25 • RS232c was DE9 • Specified by EIA in 1969 • Electricals (voltage levels) • Signaling rate, timing, slew-rate • Mechanicals • But not: character encoding, character framing, protocols Question 1: How many keys on your keyboard? Question 2: How many bits it will take to encode these? 2009 R. Gupta, UCSD

  19. What is ASCII? • American Standard Code for Information Interchange • Published in 1963, revised 1967, 1986 • 128 characters, incl. 33 non-printing or control • 94 printable characters: 26 + 10 + 11-25 symbols • Is SPACE printable? • 8-bit extension by MAC OS Roman • Unicode and Universal Character Set (UCS) • UTF-8, UTF-16, UTF-32 2009 R. Gupta, UCSD

  20. 2009 R. Gupta, UCSD

  21. Interface Basics • Who/Where to send/receive information? • Ports: mechanicals, electrical • What information to send? • Signals and Packets: Electrical signaling, logical encoding • How to send the information? • Protocols: synchronous, asynchronous How do we measure goodness of an interface? 2009 R. Gupta, UCSD

  22. 1. Ports • Which door to knock at or open? • All processors already have one door: memory • Memory-mapped IO • They may have additional I/O ports • How are these ports identified? • How are devices connecting to these ports identified? • Mechanically, Electrically, or at a ‘higher level’ • Memory-mapped versus dedicated IO • What happens to CPU when I/O operation is in progress? 2009 R. Gupta, UCSD

  23. 2. Signaling • How many wires? What do they carry? • Serial signaling: Send one bit at a time • Direction of signaling: Half and Full Duplex • Synchronous versus Asynchronous • Asynchronous serial communication • Send a START signal prior to each byte • And a STOP signal after each byte • Generally use more than 8-bit to transmit a byte (10 to 12) • UART: Universal Asynchronous Receiver Transmitter • Again, no shared clock. The RX must lock onto data and detect individual bits • TX is a Parallel-to-Series converter • RX is a Series-to-Parallel converter 2009 R. Gupta, UCSD

  24. 3. Protocols • Request/Acknowledge Handshakes • RTS = Request to Send: Transmitter (TX) asserts RTS • CTS = Clear to Send: Receiver (RX) asserts CTS • This gives you flow control • i.e., data transfer can proceed at a rate that is acceptable • Let us examine two protocols • I2C and USB 2009 R. Gupta, UCSD

  25. I2C: inter-integrated circuit 2009 R. Gupta, UCSD • Two-wire • A microcontroller can control a network of devices with just two general-purpose IO pins and software. (upto a few meters) • Connects multiple devices on a multi-drop bus • Devices can be attached or detached without affecting other devices • 7-bit address space, 16 reserved, 112 nodes maximum • 10 kbps (low), 100 kbps, 400 kbps (fast), FM+ 1 Mbps, HS 3.4 Mbps • 2008 R. Gupta, UCSD

  26. I2C Wires 2009 R. Gupta, UCSD • Two bidirectional wires • SDA: Serial Data • SCL: Serial Clock • ‘Open drain’: normally high when not in use • MASTER node issues the SCL and addresses SLAVES • SLAVE node receives the SCL and the address • “Wired AND” logical function. • 2008 R. Gupta, UCSD

  27. So, how do we write or read? 2009 R. Gupta, UCSD • Normally, both SDA and SCL are ‘high’ • “sense” before you drive a line • A device that wants to write pulls SDA low • Followed by SCL going low • So, everyone else knows that a transmission is starting • 2008 R. Gupta, UCSD

  28. START, Data, Data,…,Data, STOP! 2009 R. Gupta, UCSD

  29. Putting it together 2009 R. Gupta, UCSD • Start Condition: With SCL low, SDA goes HL • Bits are ‘sampled’ on the rising edge of SCL • Stop Condition: With SCL high, SDA goes LH • 2008 R. Gupta, UCSD

  30. Standardizing the Standard: USB • RS232C was not standard enough • Too much flexibility (on data rate, parity, flow control) • USB: standardized the door and the lane • Software takes care of the data, information side • The ‘OS’ is aware of the device interface • Up to 127 devices. One standard cable. • Devices identify themselves. Not the interface. • USB 1.1: 12 Mbps (Normal), 1.5 Mbps (Low) • USB 2.0: 480 Mbps (High) • USB 3.0: 4.8 Gbps (Super) 2009 R. Gupta, UCSD

  31. USB • Shielded 4-wire cable • One host in a network: host controller • Upstream versus downstream connection and connectors (A versus B) • Host controller either directly connects to device (star) or through a hub (tiered star) • Because of the connectors, no device-to-device connections • When a device is attached to the network • Based on its identification, the host OS determines the software driver to be used, • device is assigned a unique address and • host requests its internal configuration. 2009 R. Gupta, UCSD

  32. Classes of Devices • Host controller know about the following class of devices • Audio • HID • Hub • IrDA • Mass storage: HD, CDROM, DVD • Monitor • Communications • Physical interface device • Power • Printer • Imaging • Common class… 2009 R. Gupta, UCSD

  33. The Chip: A Packaged Part Quad Flat Pack (QFP) Ball Grid Array (BGA) http://education.netpack-europe.org/chipp.php 2009 R. Gupta, UCSD

  34. CypressPSoC I/O Pins(Each port up to 8 bits) 8-Bit CPU CoreWith RAM and ROM Blocks for processingDigital signals Blocks for processingAnalog signals All “Toys” such as ADC’s, Timers, RS232, etc. are madeout of configurable digital andanalog blocks 2009 R. Gupta, UCSD

  35. What can you do with Digital/Analog Blocks? Analog-to-Digital Converters 8- to 14-bit resolution, multiple configurations Digital-to-Analog Converters 6- to 9-bit resolution Timers, Counters, PWMs 8- to 32-bit resolution Serial Interfaces RS232, I2C, SPI Programmable Gain Amplifiers, Filters Random sequences Etc. 2009 R. Gupta, UCSD

  36. PSoC 29x66 Mechanical Characteristics 28 Pin – 3 I/O Ports 44 Pin – 5 I/O Ports 48 Pin – 6 I/O Ports 29x66-Series PSoCs come infive sizes.The primary difference is the number of I/O pins. • PDIP – Plastic Dual Inline Package • SSOP – Shrink Small Outline Package • SOIC – Small Outline Integrated Circuit • TQFP – Thin Quad Flat Pack • QFN – Quad Flat No Leads 100 Pin – 8 I/O Ports 2009 R. Gupta, UCSD

  37. Key PSoC Electrical Characteristics Supply voltage either 3.3V or 5.0V Built in controller (SMP) provides 3.3V from a single 1.5V battery or 5.0V from two 1.5V batteries Clock speed: 930 KHz – 24 MHz Can use internal oscillator or external crystal Power usage (running): 15 – 70 mW AA battery supplies about 2 Watt-Hours Around 80 hours of life on one AA Power usage (sleep): 10 – 70 uW Around 80,000 hours or 10 years of life on one AA 2009 R. Gupta, UCSD

  38. The PSoC CPU Core – M8C System Bus – 8 Bits WidePasses data between the CPU, memory, ports and peripherals Flash Memory – 32K Bytes in 29x66Holds program code (nonvolatile!)Can be used to hold user data. Supervisory ROMHolds boot-up code andcode to read from flash memory. SRAM – 2048 Bytes in 29x66Regular memory for use of CPUand peripherals. 256 bytes easilyaccessible – remainder requires paging. Interrupt ControllerAllows external events to be communicated to the CPU M8C CPU CoreExecutes instructions (arithmetic,logic, data movement, control)Modifies registers and memory Clock Sources 930KHz – 24MHzProvides basic timing for the CPUand peripheral devices. 2009 R. Gupta, UCSD

  39. Hands-on Exercise • Tasks • Design the ‘machine’ • Actually, a ‘circuit’ that connects an LED to a control SWITCH • You build the machine in a schematics editor (PSOC Designer) • Program the ‘machine’ • Write the C-code for the program that will run on the machine. • Build the ‘machine’ • Wire-wrap the connections • Download the configuration and embedded code. VLSI/CAD, Computer Architecture Software, Programming, OS Prototyping In Embedded Systems we do it all, for a given purpose: Purpose Built Machines! 2009 R. Gupta, UCSD

  40. Design the machine: Find Components and Connect in Editor 2009 R. Gupta, UCSD

  41. Program the machine • How do you make sure that the program never dies? • Repeat forever • How do you sample the switch? • Read PORT as a collection of 8-bits • Extractthe bit you want through a mask • How do you turn ON, OFF the LED? • Make calls to LED routines (written in assembly – why?) Where is the Operating System? Where does the code reside? 2009 R. Gupta, UCSD

  42. Build the machine What is a HOST computer? What happens to the ‘programmer’ after the machine is built? 2009 R. Gupta, UCSD

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