David E. Culler University of California, Berkeley

June 2008 WEI L4 - TinyOS Prog 1

Wireless Embedded Inter-Networking

Foundations of Ubiquitous Sensor Networks

TinyOS 2.0 Programing – An IPv6 Kernel Approach

David E. CullerUniversity of California, Berkeley


Example Complete Network Embedded System

MicrocontrollerAbstraction

Interface

Init/

Boo

t

PersistentAttributes &

Event Streams

DeviceAttributes &

Event Streams

Mot

or

Ligh

t

Blo

cks

Vib

ratio

n

Log

s

File

s

DeviceAbstraction

Interface

Core OSInterface

ServiceInterface

Flash Radio Serial Sensor / ActuatorC

omm

and

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Att

ribut

es

Eve

nts

Dis

cove

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NetworkEpidemics and Routing

Mes

sage

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Man

agem

ent

&

Pow

er

Domain-Specific Application Components

Net

Pro

g

Links

Do

ma

in-S

pec

ific

Dev

ice

Dri

vers

Telos micaZ imote2 other

SPI i2cuarttimersched ADC

resource


Outline

• Key TinyOS Concepts

• TinyOS Abstraction Architecture

• A Simple Event-Driven Example

• Execution Model

• Critical system elements– Timers, Sensors, Communication

• Service Architecture


TinyOS 2.0

• Primary Reference: http://www.tinyos.net/tinyos-2.x/doc/

• http://www.tinyos.net/tinyos-2.x/doc/html/tutorial/

• http://nescc.sourceforge.net/papers/nesc-ref.pdf

http://www.tinyos.net/tinyos-2.x/doc/html/tutorial/

http://www.tinyos.net/tinyos-2.x/doc/html/tutorial/


Key TinyOS Concepts

• Application / System = Graph of Components + Scheduler

• Module: component that implements functionality directly

• Configuration: component that composes components into a larger component by connecting their interfaces

• Interface: Logically related collection of commands and events with a strongly typed (polymorphic) signature

– May be parameterized by type argument

– Provided to components or Used by components

• Command: Operation performed (called) across components to initiate action.

• Event: Operation performed (signaled) across components for notification.

• Task: Independent thread of control instantiated within a component. Non-preemptive relative to other task.

• Synchronous and Asynchronous contexts of execution.


TinyOS Abstraction Architecture

• HPL – Hardware Presentation Layer– Components that encapsulate physical hardware units

– Provide convenient software interface to the hardware.

– The hardware is the state and computational processes.

– Commands and events map to toggling pins and wires

• HAL –Hardware Abstraction Layer– Components that provide useful services upon the basic HW

– Permitted to expose any capabilities of the hardware

» Some platforms have more ADC channels, Timers, DMA channels, capture registers, …

– Logically consistent, but unconstrained

• HIL – Hardware Independent Layer– Components that provide well-defined services in a manner

that is the same across hardware platforms.

– Implement common interfaces over available HAL


Illustration


TinyOS – a tool for defining abstractions

• All of these layers are constructed with the same TinyOS primitives.

• We’ll illustrate them from a simple application down.

• Note, components are not objects, but they have strong similarities.

– Some components encapsulate physical hardware.

– All components are allocated statically (compile time)

» Whole system analysis and optimization

– Logically, all components have internal state, internal concurrency, and external interfaces (Commands and Events)

– Command & Event handlers are essentially public methods

– Locally scoped

» Method invocation and method hander need not have same name (like libraries and objects)

» Resolved statically by wiring• Permits interpositioning


Platform is a collection of Chips

• TinyOS 2.x components provide the capabilities of the chips.

• TinyOS 2.x components glue to together those capabilities into a consistent system.

• TinyOS 2.x components provide higher level capabilities and services


Overall System Configuration (std)


TinyOS IPv6 Network Kernel

ActuatorActuatorSensorsSensorsTimer FlashRadio Sensor Actuator

• Network Kernel– Manages communication and storage

– Scheduler (decides when to signal events)

IPv6 Network Kernel DriverDriverDriverDriverDriver Driver

Application


Illustration of TinyOS Programming Concepts


A simple event-driven module – BlinkM.nc

• Coding conventions: TEP3

#include "Timer.h"module BlinkM{ uses interface Boot; uses interface Timer<TMilli> as Timer0; uses interface Leds;}implementation{ event void Boot.booted() { call Timer0.startPeriodic( 250 ); }

event void Timer0.fired() { call Leds.led0Toggle(); }

BlinkM

Timer0Boot Leds

Module

Module name

Interfaces• Boot• Timer• Leds

Internal name of external interface


A simple event-drvien module (cont)

#include "Timer.h"module BlinkM{ uses interface Boot; uses interface Timer<TMilli> as Timer0; uses interface Leds;}implementation{ event void Boot.booted() { call Timer0.startPeriodic( 250 ); }

event void Timer0.fired() { call Leds.led0Toggle(); }

BlinkM

Timer0Boot Leds

Two Event Handlers

Each services external eventby calling command on some subsystem

? ? ?


Simple example: Boot interface

• $tinyOS-2.x/tos/interfaces/

• Defined in TEP 107 – Boot Sequence

• Consists of a single event.

• Hardware and operating system actions prior to this simple event may vary widely from platform to platform.

• Allows module to initialize itself, which may require actions in various other parts of the system.

interface Boot { /** * Signaled when the system has booted successfully. Components can * assume the system has been initialized properly. Services may * need to be started to work, however. * * @see StdControl * @see SplitConrol * @see TEP 107: Boot Sequence */

event void booted();}


Simple example: LEDs interface

• $tinyOS-2.x/tos/interfaces/• set of Commands

– Cause action– get/set a physical attribute (3 bits)

• async => OK to use even within interrupt handlers• Physical wiring of LEDs to microcontroller IO pins may vary=> We will implement a simplified version

#include "Leds.h"

interface Leds { async command void led0On(); async command void led0Off(); async command void led0Toggle(); async command void led1On(); ... /* * @param val a bitmask describing the on/off settings of the LEDs */

async command uint8_t get(); async command void set(uint8_t val);}


Timer

• $tinyOS-2.x/tos/lib/timer/Timer.nc• Rich application timer service built upon lower level capabilities that may be very

different on different platform– Microcontrollers have very idiosyncratic timers

• Parameterized by precision

interface Timer<precision_tag>{ command void startPeriodic(uint32_t dt); event void fired(); command void startOneShot(uint32_t dt); command void stop();

command bool isRunning(); command bool isOneShot(); command void startPeriodicAt(uint32_t t0, uint32_t dt); command void startOneShotAt(uint32_t t0, uint32_t dt); command uint32_t getNow(); command uint32_t gett0(); command uint32_t getdt();}


TinyOS Directory Structure

• tos/system/ - Core TinyOS components. This directory's

– components are the ones necessary for TinyOS to actually run.

• tos/interfaces/ - Core TinyOS interfaces, including– hardware-independent abstractions. Expected to be heavily used not

just by tos/system but throughout all other code. tos/interfaces should only contain interfaces named in TEPs.

• tos/platforms/ - code specific to mote platforms, but chip-independent.

• tos/chips/***/ - code specific to particular chips and to chips on particular platforms.

• tos/lib/***/ - interfaces and components which extend the usefulness of TinyOS but which are not viewed as essential to its operation.

• apps/, apps/demos, apps/tests, apps/tutorials.


Kernel Overlay for this course

• Trunk– Kernel

» Include

» Interfaces

» Lib

» Make

» Src

» Tools

– TOS: TinyOS code that we will work with

» Drivers – abstractions of phyisical hardware• Epic

• Telosb

» Lib – Useful serves

» App*

– Binaries – precompiled tinyos Apps

– Unix


Timers

• Timers are a fundamental element of Embedded Systems– Microcontrollers offer a wide range of different hardware features

– Idiosyncratic

• Logically Timers have – Precision- unit of time the present

– Width - # bits in the value

– Accuracy- how close to the precision they obtain

• TEP102 defines complete TinyOS timer architecture

• Direct access to low-level hardware

• Clean virtualized access to application level timers

#include "Timer.h“

…typedef struct { } TMilli; // 1024 ticks per second typedef struct { } T32khz; // 32768 ticks per secondtypedef struct { } TMicro; // 1048576 ticks per second

http://www.tinyos.net/tinyos-2.x/doc/html/tep102.html


Example – multiple virtual timers#include "Timer.h"

module Blink3M{ uses interface Timer<TMilli> as Timer0; uses interface Timer<TMilli> as Timer1; uses interface Timer<TMilli> as Timer2; uses interface Leds; uses interface Boot;}implementation{ event void Boot.booted() { call Timer0.startPeriodic( 250 ); call Timer1.startPeriodic( 500 ); call Timer2.startPeriodic( 1000 ); }

event void Timer0.fired() { call Leds.led0Toggle(); } event void Timer1.fired() { call Leds.led1Toggle(); } event void Timer2.fired() { call Leds.led2Toggle(); }}


Composition

• Our event-driven component, Blink, may be built directly on the hardware

– For a particular microcontroller on a particular platform

• or on a simple layer for a variety of platforms

• or on a full-function kernel

• Or it may run in a simulator on a PC,

• Or…

• As long as it is wired to components that provide the interfaces that this component uses.

• And it can be used in a large system or application


Configuration

• Generic components create service instances of an underlying service. Here, a virtual timer.

• If the interface name is same in the two components, only one need be specified.

configuration BlinkAppC{}implementation{ components MainC, BlinkM, LedsC; components new TimerMilliC() as Timer;

BlinkM -> MainC.Boot; BlinkM.Leds -> LedsC; BlinkM.Timer0 -> Timer.Timer;}

BlinkM

Timer0Boot Leds

MainCBoot

LedsC

Leds

Timer

Timer

BlinkAppC


A Different Configuration

• Same module configured to utilize a very different system substrate.

configuration blinkC{}

implementation{ components blinkM; components MainC; components Kernel;

blinkM.Boot -> Kernel.Boot; blinkM.Leds -> Kernel.Leds; components new TimerMilliC(); blinkM.Timer0 -> TimerMilliC.Timer;}

BlinkM

Timer0Boot Leds

TimerMillic

Timer

BlinkC

Kernel

Boot Leds


Execution Behavior

• Timer interrupt is mapped to a TinyOS event.– Handled in a safe context

• Performs simple operations.

• When activity stops, entire system sleeps– In the lowest possible sleep state

• Never wait, never spin. Automated, whole-system power management.


Module state

• Private scope• Sharing through

explicit interface only!– Concurrency,

concurrency, concurrency!

– Robustness, robustness, robustness

• Static extent• HW independent type

– unlike int, long, char

module BlinkC {

uses interface Timer<TMilli> as Timer0;

uses interface Leds;

users interface Boot;

}

implementation

{

uint8_t counter = 0;

event void Boot.booted()

{

call Timer0.startPeriodic( 250 );

}

event void Timer0.fired()

{

counter++;

call Leds.set(counter);

}

}


TinyOS / NesC Platform Independent Types

• Common numeric types

• Bool, …

• Network Types– Compiler does the grunt work to map to canonical form

http://nescc.sourceforge.net


Events• Call commands

• Signal events

• Provider of interface handles calls and signals events

• User of interface calls commands and handles signals

module BlinkM {

uses interface Timer<TMilli> as Timer0;

uses interface Leds;

uses interface Boot;

provides interface Notify<bool> as Rollover;

}

implementation

{

uint8_t counter = 0;

event void Boot.booted()

{ call Timer0.startPeriodic( 250 ); }

event void Timer0.fired()

{

counter++;

call Leds.set(counter);

if (!counter) signal Rollover.notify(TRUE);

}

}

BlinkM

Timer0Boot Leds

Rollover

Notify


Examples - Event-Driven Execution

Hardware

Phy

Link

Network

Transport

HplSignal

RadioFlash MCU

Ports ADCTimers

Sof

twar

e

Kernel

HTTP – application protocol

Web Server Application

Drivers

Data Presentation

Hardware

Phy

Link

Network

Transport

HplSignal

RadioFlash MCU

Ports ADCTimers

Sof

twar

e

Kernel



Drivers

Data Presentation

Start

Timer Fire

TCP

Bind

recv

Start

Service request


Split-Phase Operations

• For potentially long latency operations– Don’t want to spin-wait, polling for completion– Don’t want blocking call - hangs till completion– Don’t want to sprinkle the code with explicit sleeps and yields

• Instead,– Want to service other concurrent activities will waiting– Want to go sleep if there are none, and wake up upon

completion

• Split-phase operation– Call command to initiate action– Subsystem will signal event when complete

• The classic concurrent I/O problem, but also want energy efficiency.

– Parallelism, or sleep.– Event-driven execution is fast and low power!


Examples/* Power-hog Blocking Call */

if (send() == SUCCESS) {

sendCount++;

}

/* Split-phase call */

// start phase

…

call send();

…

}

//completion phase

void sendDone(error_t err) {

if (err == SUCCESS) {

sendCount++;

}

}

/* Programmed delay */

state = WAITING;

op1();

sleep(500);

op2();

state = RUNNING

state = WAITING;

op1();

call Timer.startOneShot(500);

command void Timer.fired() {

op2();

state = RUNNING;


Examples - Split-Phase

Hardware

Phy

Link

Network

Transport

HplSignal

RadioFlash MCU

Ports ADCTimers

Sof

twar

e

Kernel



Drivers

Data Presentation

Hardware

Phy

Link

Network

Transport

HplSignal

RadioFlash MCU

Ports ADCTimers

Sof

twar

e

Kernel



Drivers

Data Presentation

Sample

Ready

Read

ReadDone


Sensor Readings

• Sensors are embedded I/O devices– Analog, digital, … many forms with many interfaces

• To obtain a reading– configure the sensor

» and/or the hardware module it is attached to, • ADC and associated analog electronics

• SPI bus, I2C, UART

– Read the sensor data

• TinyOS 2.x allows applications to do this in a platform-independent manner


Read Interface

• Split-phase data acquisition of typed values

• Flow-control handshake between concurrent processed– Hardware or software

• $tinyOS-2.x/tos/interface/read.nc

interface Read<val_t> {

/* Initiates a read of the value.

* @return SUCCESS if a readDone() event will eventually come back.

*/

command error_t read();

/**

* Signals the completion of the read().

*

* @param result SUCCESS if the read() was successful

* @param val the value that has been read

*/

event void readDone( error_t result, val_t val );

}


Example#include "Timer.h"module SenseM{ uses { interface Boot; interface Leds; interface Timer<TMilli>; interface Read<uint16_t>; }}implementation{ #define SAMPLING_FREQUENCY 100 event void Boot.booted() { call Timer.startPeriodic(SAMPLING_FREQUENCY); }

event void Timer.fired() { call Read.read(); }

event void Read.readDone(error_t result, uint16_t data) { if (result == SUCCESS){ call Leds.set(data & 0x07);} }}

• What does it sense?


Temp example configuration

configuration TempDispAppC { } implementation { components SenseM, MainC, LedsC, new TimerMilliC() as Timer, TempC ;

SenseM.Boot -> MainC; SenseM.Leds -> LedsC; SenseM.Timer -> TimerMilliC; SenseM.Read -> TempC;}

SenseM

Timer0Boot Leds

MainCBoot

LedsC

Leds

Timer

Timer

TempDispAppC

Read

TempC

Read


Concurrency

• Commands and event glue together concurrent activities

• Hardware units operate on parallel– Commands used to initiate activity

– Events used to signal completion, etc.

• System software components are very similar– But they don’t have dedicated hardware to keep working on

the command.

– Tasks are used for that

• Decouple execution and leave room for juggling– Use lots of little tasks to keep things flowing

• Preempted by async events (interrupts)– Not other tasks


Tasks – Crossing the Asynch / Synch Boundary

module UserP { provides interface Button; uses interface Boot; uses interface Msp430Port as Pin; uses interface Msp430PortInterrupt as PinInt;}

implementation { event void Boot.booted() { call Pin.setDirection(0); /* Input */ call PinInt.edge(1); /* Rising edge, button release */ call PinInt.enable(1); /* Enable interrupts */ }

task void fire() { signal Button.pressed(); /* Signal event to upper layers */ } async event void PinInt.fired() { post fire(); }}


Examples - Tasks

Hardware

Phy

Link

Network

Transport

HplSignal

RadioFlash MCU

Ports ADCTimers

Sof

twar

e

Kernel



Drivers

Data Presentation

Hardware

Phy

Link

Network

Transport

HplSignal

RadioFlash MCU

Ports ADCTimers

Sof

twar

e

Kernel



Drivers

Data Presentation

Sample

Ready

fired

readDone

serviceReqnotify

fired


Tasks• Need to juggle many potentially

bursty events.• If you cannot get the job done

quickly, record the parameters locally and post a task to do it later.

• Tasks are preempted by lower level (async) events.

– Allow other parts of the system to get the processor.

– Without complex critical semaphores, critical sections, priority inversion, schedulers, etc.

/* BAD TIMER EVENT HANDLER */

event void Timer0.fired() {

uint32_t i;

for (i = 0; i < 400001; i++) {

call Leds.led0Toggle();

}

}

Hardware

Interrupts

even

ts

commands

Tasks

/* Better way to do a silly thing */

task void computeTask() {

uint32_t i;

for (i = 0; i < 400001; i++) {}

}

event void Timer0.fired() {

call Leds.led0Toggle();

post computeTask();

}


Uses of tasks (???)

• High speed sampling

• Filtering

• Queueing

• Smoothing

• Detection

• Classification

• …


Networking

• Traditional TinyOS communication is based on active messages

– Send a structure to <node,handlerId>

– Receive is just a network event that signals the hander with a message

• Earliest TinyOS (0.3) was essentially moving Active Messages and the Threaded Abstract Machine (TAM) from the MPP domain to emdedded devices.

– Parallel Machine communication is internal!

– Sensor networks are networks, not distributed computers

– They connect to OTHER NETWORKS

• Active Messages covered in Appendix– But I don’t use them any more


Transit Network (IP or not)

Access point - Base station - Proxy

Sensor Patch

Patch Network

Data Service

Intranet/Internet (IP)

Client Data Browsingand Processing

Sensor Node

GatewayGateway

Verification links

Other information sources

Sensor Node

Canonical SensorNet Network Architecture


Typical IP Network

InternetInternet

ISP

Company Router / Firewall

externallyaccessible hosts

DMZ

WiFiWiFi

Internal Private networks

ethernet

serial linesleased linkspoint-point links

internally accessible hosts

Stand-alone networks

inaccessiblehosts

WiFIWiFI

External networksVPNtunnels


TinyOS 2x Embedded IP Architecture

GPIO Pins

Ext. INT

ADCSPI, i2c,UART

Low-Power 802.15.4

Vir

tua

lm

s T

imer

s Timer

RTCS

che

dul

er

Fla

shS

tora

ge

arbiters

Pw

r M

gr

UDP/TCP L4Basic Health &Mgmt Services Basic

ConfigurationServices

Sensor Drivers

OTAIP 6LowPAN L2

IP route L3

Higher Level Embedded Web Services


WSNs in an IP context

InternetInternet

Stand-alone embedded networks

monitoring devices

ad hocembedded

network

controllers& analytics

IP-basedembedded

network

monitoring devices

ad hocembedded

network

controllers& analytics

IP-basedembedded

network

Router /Firewall

gatewaycomputer

IP-basedcorporatenetworks

InternetInternet

IP-basedcorporatenetworks

Internally connected embedded networks


Issues in Communication Abstraction• Names

– What are they?– What do they mean? What is their scope?– How are they allocated?– How are they translated into useful properties

» Address? Physical Resource?

• Storage– Transmit

» When can it be reused? How do you know? What do you do when it is full?

– Receive» When is it allocated? Reclaimed? By whom? What

happens when it overflows?– Asynchronous event

» How do you know that something has arrived?

• Many more issues in actually performing the requested communication


Answers: Naming

• TinyOS Active Messages– TOS_local_addr, 16 bits, only within “a network”, allocated at

program download time– Scope limited to TOS_group, within PAN, Channel, and

physical extent.– The standards that try to do it all with IEEE 802.15.4 16 bit

short address are not much better

• IP Architecture– Link name: IEEE 802.15.4 => EUID64 & SA16

» EUID64 globally unique, SA16 assigned to be unique over the PAN

– Net name: IP address» Prefix | Interface Id» Must be unique within routability extent» Several IP address: Link Local, Global, Multicast, …

- Service name: Port- Hostname Translated to IP by DNS


Answers: Storage

• TinyOS Active Messages– Sender app allocates send buffer, OS owns it till sendDone

event

– OS provides App with recv buffer, app must return it or a replacement

• BSD Sockets– Sender app allocate buffer, copied to kernel on send

– Receiver allocates buffer and passes pointer to kernel, kernel copies

– Additional sets of buffer managed within the kernel

• TinyOS Sockets ???


UDP Interface

• Wiring to a UDP interface is enough for sendto• Standard Unix sockaddr_in6_t• Bind – associates the component that uses the interface with the port

– Starts receiving whatever datagrams come in on it

• Sendto sends a datagram from a buf to a IP destination– Neighbor, intra-PAN, inter-network (wherever it needs to go!)– Linklocal address is 1-hop neighbor– Pan-wide routable prefix– Error when not in network or overrun transmit resources

• Recvfrom gets a buffer with a datagram and metadata about it• Able to fill the 15.4 frame without knowing details of header

compression

interface Udp { command error_t bind( uint16_t port ); command uint16_t getMaxPayloadLength( const sockaddr_in6_t *to ); command error_t sendto( const void *buf, uint16_t len, const sockaddr_in6_t *to ); event void recvfrom( void *buf, uint16_t len, sockaddr_in6_t *from,

link_metadata_t *metadata );}


And what about TCP

• UDP is a datagram transport– Essentially the same as AM

– Fits naturally in event-driven model

– Can use NesC platform independent data structure to have unambiguous packet formats without hton / ntoh error prone bit twiddling.

• But TCP is a stream protocol…


TCP Interface

• Transitions of the TCP protocol reflected as events• Recv per segment• Send is NOT SPLIT PHASE !!!

– More on this later

interface Tcp { command error_t bind(uint16_t port, uint8_t *buf, uint16_t bufsize); event bool accept( sockaddr_in6_t *to ); command error_t connect( const sockaddr_in6_t *to, uint8_t *buf,

uint16_t bufsize ); event void connected(); command error_t send( const void *buf, uint16_t len ); event void acked(); event uint16_t recv( void *buf, uint16_t len ); command error_t close( bool force ); event void closed(); }


Example TinyOS Service Architecture

HardwareAbstraction

Layer

Basic OSinterface

ServiceAPI

Flash Radio / Uart Sensor/Actuator

Volumes Buses & ADCsLinks

File

s

Logs

RF

Ligh

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Sou

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Oth

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Com

man

ds

Att

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Dis

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Blo

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OT

A p

rogr

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NetworkM

essa

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Hardware

Man

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Pw

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Application


Permanent Data Storage

• TinyOS 2.x provides three basic storage abstractions: – small objects,

– circular logs, and

– large objects.

• also provides interfaces the underlying storage services and components that provide these interfaces.

• Flash devices– ST Microelectronics M25Pxx family of flash memories used in the

Telos family of motes (tos/chips/stm25p)

– Atmel AT45DB family of flash memories used in the Mica2/MicaZ motes (tos/chips/at45b)

– Special pxa271p30 versions for the Intel Mote2 contributed by Arch Rock. (tos/platforms/intelmote2)

• TEP103


Storage Interfaces and Components

• Interfaces– BlockRead

– BlockWrite

– Mount

– ConfigStorage

– LogRead

– LogWrite

– Storage.h

Components– ConfigStorageC - Configuration Data

» calibration, identity, location, sensing configuration, ..

– LogStorageC

» data

– BlockStorageC

» Code, …

http://www.tinyos.net/tinyos-2.x/tos/interfaces/BlockRead.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/BlockWrite.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/Mount.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/ConfigStorage.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/LogRead.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/LogWrite.nc

http://www.tinyos.net/tinyos-2.x/tos/types/Storage.h

http://www.tinyos.net/tinyos-2.x/tos/chips/stm25p/ConfigStorageC.nc

http://www.tinyos.net/tinyos-2.x/tos/chips/stm25p/LogStorageC.nc

http://www.tinyos.net/tinyos-2.x/tos/chips/stm25p/BlockStorageC.nc


Volumes

• TinyOS 2.x divides a flash chip into one or more fixed-sized volumes that are specified at compile-time using an XML file.


Example – blink period config

Define config storage object

chipname.xml file

Added to the TinyOS configuration

New interfaces for the module

Wire to the new interfaces


On boot – Mount and Read


Config data – done, write, commit


Network Embedded Systems

HardwareAbstraction

Layer

Basic OSinterface

ServiceAPI



File

s

Logs

RF

Ligh

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Com

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Att

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Dis

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NetworkM

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Hardware

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Application


IP/6LoWPAN “Kernel Component”component KernelC { provides interface Boot; provides interface Timer<TMilli> as TimerMilli[ uint8_t id ]; provides interface TaskBasic[ uint8_t id ]; provides interface GlobalTime<TMilli>; /* Global Time – NTP */ provides interface LocalIeeeEui64; /* EUI MAC Address */ provides interface Udp as Udp0; /* Udp */ provides interface Udp as Udp1; provides interface Tcp as Tcp0; /* Tcp */ provides interface Tcp as Tcp1; provides interface IPv6Addresses; /* IPv6 Utility Functions */ provides interface IPv6Notify; /* MCU generated interrupts */ provides interface HplSignal as HplSignalAdc12; provides interface HplSignal as HplSignalPort1; provides interface HplSignal as HplSignalPort2; provides interface HplSignal as HplSignalTimerA0; provides interface HplSignal as HplSignalTimerA1; provides interface HplSignal as HplSignalTimerB0; provides interface HplSignal as HplSignalTimerB1;}


TinyOS IPv6 Network Kernel

ActuatorActuatorSensorsSensorsTimer FlashRadio Sensor Actuator

• Network Kernel– Manages communication and storage

– Scheduler (decides when to signal events)

IPv6 Network Kernel DriverDriverDriverDriverDriver Driver

Application


Network Embedded Systems

HardwareAbstraction

Layer

Basic OSinterface

ServiceAPI



Con

fig

Logs

RF

Ligh

t

Sou

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6LoWPAN Network

Hardware

Man

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Application

ICMP / UDP / TCP

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Our kernelboundary


TinyOS Concepts not yet covered

• Generic Components– Generic modules and generic configurations

– Multiple instances

– Type polymorphism

– Storage and configuration

– Discovery

• Parameterized interfaces– Index array of interfaces to other components

– Dispatch, services

– Virtualization

• Platform independent structs– Replace xdr and all that

– Eliminate error prone bit twiddling


Discussion


Traditional TinyOS Active Messages


Sensor NETWORK

• We have a flexible, low-power, event-driven sensor / actuator platform.

• Let’s add the network

• Send / Receive of information

• Dispatching incoming data to computation processes that will handle it.

– Automate in a systematic fashion

• Parsing the packet– Define the structure, let the compiler do the work.

– Handler knows what it should be receiving


message_t structure• Packet - Provides the basic accessors for the message_t

abstract data type. This interface provides commands for clearing a message's contents, getting its payload length, and getting a pointer to its payload area.

• Send - Provides the basic address-free message sending interface. This interface provides commands for sending a message and canceling a pending message send. The interface provides an event to indicate whether a message was sent successfully or not. It also provides convenience functions for getting the message's maximum payload as well as a pointer to a message's payload area.

• Receive - Provides the basic message reception interface. This interface provides an event for receiving messages. It also provides, for convenience, commands for getting a message's payload length and getting a pointer to a message's payload area.

• PacketAcknowledgements - Provides a mechanism for requesting acknowledgements on a per-packet basis.

• RadioTimeStamping - Provides time stamping information for radio transmission and reception.

http://www.tinyos.net/tinyos-2.x/tos/interfaces/Packet.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/Send.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/Receive.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/PacketAcknowledgements.nc

http://www.tinyos.net/tinyos-2.x/tos/interfaces/RadioTimeStamping.nc


Active Messages - Dispatching messages to their handlers• AM type – dispatch selector

– Frame_type at link layer

– IP Protocol Field at network layer

– Port at Transport layer

• AM_address

• AMPacket - Similar to Packet, provides the basic AM accessors for the message_t abstract data type. This interface provides commands for getting a node's AM address, an AM packet's destination, and an AM packet's type. Commands are also provides for setting an AM packet's destination and type, and checking whether the destination is the local node.

• AMSend - Similar to Send, provides the basic Active Message sending interface. The key difference between AMSend and Send is that AMSend takes a destination AM address in its send command.

http://www.tinyos.net/tinyos-2.x/tos/interfaces/AMPacket.nc


Communication Components

• AMReceiverC - Provides the following interfaces: Receive, Packet, and AMPacket.

• AMSenderC - Provides AMSend, Packet, AMPacket, and PacketAcknowledgements as Acks.

• AMSnooperC - Provides Receive, Packet, and AMPacket.

• AMSnoopingReceiverC - Provides Receive, Packet, and AMPacket.

• ActiveMessageAddressC - Provides commands to get and set the node's active message address. This interface is not for general use and changing the a node's active message address can break the network stack, so avoid using it unless you know what you are doing.


HAL to HIL

• Since TinyOS supports multiple platforms, each of which might have their own implementation of the radio drivers, an additional, platform-specific, naming wrapper called ActiveMessageC is used to bridge these interfaces to their underlying, platform-specific implementations. ActiveMessageC provides most of the communication interfaces presented above.

• Platform-specific versions of ActiveMessageC, as well the underlying implementations which may be shared by multiple platforms (e.g. Telos and MicaZ) include:

– ActiveMessageC for the intelmote2, micaz, telosa, and telosb are all implemented by CC2420ActiveMessageC.

– ActiveMessageC for the mica2 platform is implemented by CC1000ActiveMessageC.

– ActiveMessageC for the eyesIFX platform is implemented by Tda5250ActiveMessageC.


tos/types/message.h.

• Link level concept used throughout the TinyOS research community and industry.

• How does this move forward to IP/WSN?

typedef nx_struct message_t {

nx_uint8_t header[sizeof(message_header_t)];

nx_uint8_t data[TOSH_DATA_LENGTH];

nx_uint8_t footer[sizeof(message_header_t)];

nx_uint8_t metadata[sizeof(message_metadata_t)];

} message_t;


Sending a packet to the neighborhood#include <Timer.h>#include "BlinkToRadio.h"

module BlinkToRadioC { uses interface Boot; uses interface Leds; uses interface Timer<TMilli> as Timer0; uses interface Packet; uses interface AMPacket; uses interface AMSend; uses interface Receive; uses interface SplitControl as AMControl;}implementation { uint16_t counter; message_t pkt; bool busy = FALSE;

event void Boot.booted() { call AMControl.start(); } event void AMControl.startDone(error_t err) { if (err == SUCCESS) { call Timer0.startPeriodic(TIMER_PERIOD_MILLI); } }


Sending a packet to the neighborhood event void Timer0.fired() { counter++; if (!busy) { BlinkToRadioMsg* btrpkt = (BlinkToRadioMsg*)(call Packet.getPayload(&pkt, NULL)); btrpkt->nodeid = TOS_NODE_ID; btrpkt->counter = counter; if (call AMSend.send(AM_BROADCAST_ADDR, &pkt, sizeof(BlinkToRadioMsg)) == SUCCESS) { busy = TRUE; } } }

event void AMSend.sendDone(message_t* msg, error_t err) { if (&pkt == msg) { busy = FALSE; } }

event message_t* Receive.receive(message_t* msg, void* payload, uint8_t len){ if (len == sizeof(BlinkToRadioMsg)) { BlinkToRadioMsg* btrpkt = (BlinkToRadioMsg*)payload; call Leds.set(btrpkt->counter & 0x7); } return msg; }}


Receive – a network event

• Service the incoming message– Automatically dispatched by type to the handler

• Return the buffer– Or if you want to keep it, you need to return another one.

• Overlay a network type structure on the packet so the compiler does the parsing.

event message_t* Receive.receive(message_t* msg, void* payload, uint8_t len) {

if (len == sizeof(BlinkToRadioMsg)) {

BlinkToRadioMsg* btrpkt = (BlinkToRadioMsg*)payload;

call Leds.set(btrpkt->counter);

}

return msg;

}

enum { AM_BLINKTORADIO = 6, };

typedef nx_struct BlinkToRadioMsg {

nx_uint16_t nodeid;

nx_uint16_t counter;

} BlinkToRadioMsg;


Communication-Centric Operating Systems Design Elements• Packets cross between different kinds of machines

– Small Endian vs Large Endian– Representation of data types – int, long, char, …

• Protocols have specific message formats Network Types Overlay network type struct on the packet and let the compiler do the

shifting, masking, and endian conversion Eliminate error-prone parsing code

• Protocols are realized by state machines that advance on message events

– Make external communication events as simple as internal events

• Network stacks involve dispatching on types at several levels

– Frame type, Protocol Number, port number– Provide support for dispatch

• Packet events are intrinsically connected with buffer management

– Make is a robust and simple as possible.


AM_ID – port number#include <Timer.h>

#include "BlinkToRadio.h"

configuration BlinkToRadioAppC {

}

implementation {

components MainC, LedsC;

components BlinkToRadioC as App;

components new TimerMilliC() as Timer0;

components ActiveMessageC;

components new AMSenderC(AM_BLINKTORADIO);

components new AMReceiverC(AM_BLINKTORADIO);

App.Boot -> MainC;

App.Leds -> LedsC;

App.Timer0 -> Timer0;

App.Packet -> AMSenderC;

App.AMPacket -> AMSenderC;

App.AMControl -> ActiveMessageC;

App.AMSend -> AMSenderC;

App.Receive -> AMReceiverC;

}


Indexed interfaces for dispatch

• Clients & Applications have individual view

• Provider has global view

Active Message

Network Stack Implementation

Hardware

SVC x SVC y SVC z SVC w


Active Messages

• Concept – message carries unique identifier of handler that is to process it

– Directly off the link

– Compile time formation and parsing

» It is a Structure

– Bounded storage

» Consume the receive buffer immediately

• Has been the central networking abstraction in all version of TinyOS

– Used for all the multihop routing protocols, …

• Link frame derived from SW usage

• TCP/UDP / IP / 6LoWPAN will cause first serious re-examination of Message_T


Parameterized Wiring

• Active Message clients wire to distinct AM_id– Unique ID of the service handler

• Many other system services provided to multiple clients (independently) but do not need a “protocol id”

• NesC “Unique” allocates new interfaces at compile time

– Relative to a key set

– Whole system compilation => tight resource allocation


Wiring Examples ???

Date post:	14-Jan-2016
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David E. Culler University of California, Berkeley

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