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6LoWPAN: The Wireless Embedded Internet Companion Exercise Slides Zach Shelby, Martti Huttunen

6LoWPAN: The Wireless Embedded Internet Companion Exercise Slides Zach Shelby, Martti Huttunen.

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6LoWPAN: The Wireless Embedded Internet Companion Exercise Slides Zach Shelby, Martti Huttunen

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  1. 6LoWPAN: The Wireless Embedded Internet Companion Exercise Slides Zach Shelby, Martti Huttunen This work is licensed under the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA Figures on slides with book symbol from 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann, ISBN: 978-0-470-74799-5, (c) 2009 John Wiley & Sons Ltd

  2. The Book 6LoWPAN: The Wireless Embedded Internet by Zach Shelby, Carsten Bormann Length: 254 pages Publisher: John Wiley & Sons http://www.6lowpan.net Companion web-site with blog, full companion course slides and exercises 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  3. Outline • Introduction • Embedded Devices • Operating Systems • Embedded Development • 6LoWPAN Implementation Issues • Exercise Hardware • Contiki & uIP • Exercises 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  4. Introduction 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  5. Embedded Meets Wireless • Microcontrollers are everywhere in embedded systems • appliances, watches, toys, cameras, industrial control, mobile phones, sensors, cars, automation • Microcontroller vs. microprocessor market • 15 x more microcontroller units sold yearly (8 billion) • 20 billion vs 43 billion USD market by 2009 • Possibilities of wireless are endless • 802.15.4 chips to 150 million unit sales by 2009 • Embedded systems have special characteristics • Academic community very computer science and protocol driven, often ignoring • Physical layer realities • Embedded system operation • Real-time capabilities 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  6. Embedded Devices 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  7. Device Architecture • Microcontroller and program code • Power supply • Power management • Renewable energy? • Memory (RAM, FLASH) • Sensors • Actuators • Communication • Input/output • Part of a larger system? 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  8. Microcontroller • Main processing units of embedded devices • Special purpose and highly integrated • Integrated RAM, ROM, I/O, peripherals • Extremely good power to performance ratio • Cheap, typically 0.25 - 10.00 USD • Executes programs including embedded system control, measurement & communications • Usually time-critical requiring guarantees • Real-time performance a common requirement • Pre-emptive scheduled tasks • Queues and semaphores 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  9. Example: MSP430 • Texas Instruments mixed-signal uC • 16-bit RISC • ROM: 1-60 kB • RAM: Up to 10 kB • Analogue • 12 bit ADC & DAC • LCD driver • Digital • USART x 2 • DMA controller • Timers 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  10. Example: Atmel AVR • Atmel AVR family • 8-bit RISC • RAM: Up to 4 kB • ROM: Up to 128 kB • Analogue • ADC • PWM • Digital • USARTs • Timers 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  11. Memory • Random access memory (RAM) • Included on-board in microcontrollers • Often the most valuable resource • Read-only memory (ROM) • Usually actually implemented with NOR flash memory • Flash • Eraseable programmable memory • Can be read/written in blocks • Slow during the write process • Consumes power of course! • External memory • External memory supported by some microcontrollers • Serial flash always supported 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  12. Common Bus Interfaces • Digital and analogue I/O • Accessed by port and pin number (e.g. P1.3) • Some pins are also connected to interrupts • UART • Asynchronous serial bus • After level translation it is an RS232 bus • Usually kbps up to 1 mbps • SPI (serial peripheral interface) • Synchronous serial bus • Reliable with speeds of several Mbps • I2C (inter-integrated circuit) bus • 2-wire bus with data and clock • Parallel bus • Implemented with X-bit width • X-bit address and clock signals 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  13. Communications • Embedded devices are autonomous but most often part of a larger system • Thus communications interfaces are very important in the embedded world • Wired interfaces • Serial: RS232, RS485 • LAN: Ethernet • Industrial: Modbus, Profibus, Lontalk, CAN • Wireless interfaces • Low-power: IEEE 802.15.4 (ZigBee, ISA100, Wireless HART) • WLAN: WiFi • WAN: GPRS, WiMax 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  14. Transceivers • Modern embedded communications chips are transceivers: they combine half-duplex transmission and reception. • Transceivers integrate varying functionality, from a bare analogue interface to the whole digital baseband and key MAC functions. 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  15. Important Characteristics • Level of digital integration • Power consumption and efficiency • Transition speeds and consumption • Levels of sleep • Carrier frequency and data rate • Modulation • Error coding capabilities • Noise figure and receiver sensitivity • Received signal strength indicator (RSSI) • Support for upper layers • Data and control interface characteristics 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  16. Example: RFM TR1000 • Proprietary radio at 916 MHz • OOK and ASK modulation • 30 kbps (OOK) or 115.2 kbps (ASK) operation • Signal strength indicator • Provides bit interface • Not included: • Synchronization • Framing • Encoding • Decoding 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  17. Example: CC2420 • IEEE 802.15.4 compliant radio • 2.4 GHz band using DSSS at 250 kbps • Integrated voltage regulator • Integrated digital baseband and MAC functions • Clear channel assessment • Energy detection (RSSI) • Synchronization • Framing • Encryption/authentication • Retransmission (CSMA) 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  18. Example: CC2430 • System-on-a-chip solution • Integrated 8051 microcontroller • 32 MHz Clock Speed • ADC, DAC, IOs, 2 UARTs etc. • 8 kB of RAM, up to 128 kB of ROM • Integrated IEEE 802.15.4 radio, like the CC2420 • Power consumption 10-12 mA higher than the CC2420, coming from the 8051 microcontroller • Saves cost, only about 1 EUR more expensive than the CC2420 • Internal DMA makes radio and UART performance better than with a uC + CC2420 solution 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  19. Power Consumption • Radio power consumption critical to consider • Power output level • Limited savings effect • Optimal power difficult • Must be considered globally • Transition times • Each transition costs • Power equal to RX mode • Should be accounted for 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  20. Power Consumption A simple approximation for power consumption: = Time that takes to go from sleep state to awake state = Transmitter setup time, i.e. time it takes for the transmitter to be ready = Time in the Tx state = Receiver setup time, i.e. time it takes for the receiver to be ready = Time in the Rx state = Time in the idle state = Time in the sleep state = Average number of times per frame that the transmitter is used = Average number of times per frame that the receiver is used = Duration of the time frame = Power used in the Tx state = Power used in the Rx state = Power used in the idle state = Power used in the sleep state = Average power used by the transceiver 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  21. Sensors & Actuators • Sensors measure real-world phenomena and convert them to electrical form • Analogue sensors require an ADC • Digital sensors use e.g. I2C or SPI interfaces • Human interface can also be a sensor (button) • IEEE 1451 standard becoming important • Defines standard interfaces and auto-configuration • Also some protocol specifications • Actuators convert an electrical signal to some action • Analogue and digital interfaces both common • A motor servo is a good example 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  22. Operating Systems 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  23. Real-time Operating Systems • Library vs. operating system • Operating system manages all resources • Embedded systems have pre-defined tasks • Designed to optimize size, cost, efficiency etc. • Real-time • Real-time OS provides tools to meet deadlines • Pre-emptive, queues, semaphores • Concurrency • Execution flows (tasks) able to run simultaneously • Threads and processes • Sockets and APIs 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  24. Real-time Issues • Wireless embedded systems usually are real-time • Watch, robot, building sensor, control node • A RTOS only facilitates real-time system creation • Still requires correct software development • RTOS is not necessarily high performance • Can meet general system deadlines (soft real-time) • or deterministically (hard real-time) • Deadlines can be met using • Specialized pre-emptive scheduling algorithms • Proper inter-task design & communication • Semaphores and queues to avoid racing 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  25. Real-time Issues 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  26. Concurrency • Concurrency occurs when two or more execution flows run simultaneously • It introduces many problems such as • Race conditions from shared resources • Deadlock and starvation • OS needs to coordinate between tasks • Data exchange, memory, execution, resources • There are two main techniques • Process based • CPU time split between execution tasks • Embedded systems typically use lighter threads • Event based 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  27. Concurrency • Process based • Event based 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  28. OS Examples • Example embedded operating systems • Contiki (www.sics.se/~adam/contiki) • FreeRTOS (www.freertos.org) • TinyOS (www.tinyos.org) • and thousands of others... • For higher powered MCUs (e.g. ARMs) • VX Works • Microcontroller Linux (Android, Maemo etc.) • Windows CE • Symbian 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  29. Embedded Development 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  30. Embedded Development Objects Binary Compiler Linker Programmer Sources 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  31. Embedded Development • Software resides in system non-volatile memory • External or internal flash/eeprom/prom memories • Modern microcontrollers are capable of writing the internal flash memory run-time and often do not have an external memory bus • Development is done outside the system • Cross-compilers are used to create binary files • Cross-compiler creates binary files for a different architecture than it is running on • Various commercial and free compilers available • System is programmed by uploading the binary • In-system programming tools or external flashers 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  32. Cross-compiler Environments • Integrated development environments (IDEs)‏ • Commercial compilers are usually of this type • Usually dependent on a specific OS (Windows)‏ • Integrate a text editor, compiler tools and project management along with C library • System programmer tool usually tightly integrated • Also open-source IDEs available • Open-source IDEs usually employ “plugin” architecture • General-purpose extensible environments • Include scripting tools for running any command line tools: compilers, linkers, external editors and programmers • Example: Eclipse (implemented in Java) 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  33. Cross-compiler Environments • Command line utilities • Separate compiler/linker, editor and project management tools, architecture-dependent C library • Project management: make • make is an automated software building tool • Based on target-dependency-operation style blocks • Allows use of project templates and separate platform build rules by using “include files” • Most common way of managing open-source software projects • automake and autoconf tools extend functionality to platform-independent software development 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  34. Cross-compiler Environments • Command line compilers • most common is gcc: available for a multitude of microcontroller and -processor architectures • sdcc: Small Device C Compiler: PICs, 8051's etc. • single-architecture compilers • System programming tools • usually specific to a single microcontroller family • vary greatly in their ease of use and interface type • most require some sort of programming cable or a programmer device to upload software • dependent on the microcontroller programming algorithm • standard buses (SPI, UART, JTAG) vs. proprietary buses 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  35. Cross-compiler Environments • Command-line tools vs. (commercial) IDEs • IDEs are easily accessible: single installer, single GUI • Commercial IDEs vary greatly in usability, standards compliance and are (usually) tied to a single architecture -> bad portability • Most commercial IDEs don't really support templates • Programmer must go through various dialogs to create a new project • Often project files can not just be copied (contain directory paths and such) and may be binary format • Command line tools have a steeper learning curve • Once learned, applicable to most architectures • Higher flexibility and ease of duplicating projects 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  36. Cross-compiler Issues • Portability • Header files may not follow standard naming • Hardware-specific header files might not be automatically selected • Most commercial IDEs use different names for each different hardware model -> difficulties in portability • gcc e.g. uses internal macros for model selection -> easier portability via environment variables, no header changes • Hardware register access and interrupt handlers • Interrupt handler declaration is compiler-dependent • Declaration format is not standardized • Can be worked around via macros (in most cases)‏ • Some compilers (and C libraries) require I/O macros • gcc ports implement direct register access modes 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  37. Open-source Tools • Various text editors available: nedit, emacs, vi ... • Project build system: make • Compilers/linkers: binutils & gcc, sdcc • binutils: as, ld, objcopy, size etc. • gcc: c compiler; uses binutils to create binary files • Standard C libraries • Provide necessary development headers and object files for linking and memory mapping • msp430-libc for MSP430, avr-libc for AVR • Programmers • AVR: uisp, avrdude • MSP430: msp430-bsl, msp430-jtag • CC2430: nano_programmer • IDE: Eclipse 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  38. SDCC Compiler • Simple Device C Compiler • http://www.sdcc.org • Specialized in 8051, PIC, HC08 etc. microcontrollers • Has CC2430 and CC2510 support • sdcc application handles both compilation and linking • Uses make build environment • Compatible with Eclipse • Support for banking (needed in 8051 with 64k+ ROM) • Thanks to Peter Kuhar for banking support 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  39. 6LoWPAN Implementation Issues 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  40. Chip Models • How to integrate 6LoPWAN into an embedded device? • Challenges: • Lack of standard interfaces (no USB or PCMCIA) • No standard operating systems (if any!) • Power consumption limitations • Price limitations • Models for integrating 6LoWPAN include SoC, two-chip or network processor • System-on-a-chip model • Everything on one chip + Maximum integration + Minimum price and size - Longer, more difficult development - Little if any portability 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  41. Chip Models • Two-chip solution • Separate radio transceiver + Free choice of uC + More portability - More expensive - App integration with stack • Network processor solution • Network stack on the radio + Free choice of uC + Application independent of the stack + Easy integration - More expensive 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  42. Contiki uIPv6 • Popular embedded OS for small microcontrollers • MSP430, AVR, PIC, 8051 etc. • http://www.sics.se/contiki • Standard C-based • Portable applications • Lightweight protothreads • uIPv6 Stack • Full IPv6 support • RFC4944 + 6lowpan-hc • UDP, TCP, ICMPv6 • Great for research 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  43. NanoStack 2.0 • Sensinode’s commercial 6LoWPAN stack • Network processor model • NAP interface over UART • Optimized for SoC radios • TI CC2430, CC2530 • TI CC1110 • Portable • IPv6/6LoWPAN stack • UDP, ICMPv6 • RFC4944, 6lowpan-hc • 6lowpan-nd • NanoMesh IP routing 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  44. Router Integration • Edge Routers interconnect the IPv6 world and 6LoWPAN • An ER needs to implement: • 6LoWPAN interface(s) • 6LoWPAN adaptation • Simple 6LoWPAN-ND • A full IPv6 protocol stack • Other typical features include: • IPv4 support and tunneling • Application proxy techniques • Extended LoWPAN support • A firewall • Management 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  45. Example Exercise Hardware 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  46. Exercise Hardware • NanoRouter USB 2.4GHz • Serial USB device • NanoStack 2.0 • High-power amplifier • NanoSensor 2.4GHz • Demo sensor node • Rechargeable batteries • 3-axis accelerometer • Light sensor • D-connector for external sensors • Support for either NanoStack or Contiki 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  47. NanoSensor D-connector • Standard 9-pin D-connector for sensor expansion • D-connector pin-out: 1 = 3.3V in/out 2 = Digital I/O or programmer connection 3 = Analog switch control. 1=external I/O in use 4 = Reset 5 = Ground 6 = A/D (Digital I/O). P0_0 7 = Digital I/O (P2_1) or programming connection 8 = UART out (from RC module) 9 = UART in (to RC module) 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  48. Contiki 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  49. What is Contiki? • Contiki is an open-source operating system/protocol stack for embedded systems • Highly portable and reasonably compact • Protocol stack configuration customizable • Originally created by Adam Dunkels, developer of the uIP stack • http://www.sics.se/contiki 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

  50. Contiki processes • Contiki core is event-driven • Interrupts and HW drivers generate events • Events are dispatched to event handlers by the Contiki core • Event handlers must return control to core as soon as possible • Co-operative multitasking • Basic processes are implemented using protothreads • Easier to create sequential operations • An abstraction to avoid complex state-machine programming • In more complex applications, the amount of states may be huge 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

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