Wireless Embedded Inter-Networking
Foundations of Ubiquitous Sensor Networks
TinyOS 2.0 Programing – An IPv6 Kernel Approach
David E. Culler
University of California, Berkeley
June 2008
WEI L4 - TinyOS Prog
1
Example Complete Network Embedded System
Radio
Serial
Motor
Light
Sensor / Actuator
Management & Power
Flash
Discovery
Events
Attributes
Links
Vibration
Blocks
Network
Epidemics and Routing
Device
Attributes &
Event Streams
Domain-Specific
Device Drivers
Device
Abstraction
Interface
Logs
Files
Core OS
Interface
Messages
Persistent
Attributes &
Event Streams
Net Prog
Init/Boot
Service
Interface
Commands
Domain-Specific Application Components
resource
Microcontroller
Abstraction
Interface
sched
Telos
June 2008
timer
uart
SPI
micaZ
imote2
WEI L4 - TinyOS Prog
i2c
ADC
other
2
Outline
•
•
•
•
•
Key TinyOS Concepts
TinyOS Abstraction Architecture
A Simple Event-Driven Example
Execution Model
Critical system elements
– Timers, Sensors, Communication
• Service Architecture
June 2008
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3
TinyOS 2.0
• Primary Reference: http://www.tinyos.net/tinyos2.x/doc/
• http://www.tinyos.net/tinyos-2.x/doc/html/tutorial/
• http://nescc.sourceforge.net/papers/nesc-ref.pdf
June 2008
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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.
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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
June 2008
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Illustration
June 2008
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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
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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
June 2008
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9
Overall System Configuration (std)
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10
TinyOS IPv6 Network Kernel
• Network Kernel
– Manages communication and storage
– Scheduler (decides when to signal events)
Application
IPv6 Network Kernel
Radio
June 2008
Timer
Flash
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Driver
Driver
Driver
Driver
Driver
Driver
Sensors
Sensors
Sensor
Actuator
Actuator
Actuator
11
Illustration of TinyOS Programming
Concepts
June 2008
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A simple event-driven module – BlinkM.nc
#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();
}
Module
Module name
Internal name
of external
interface
BlinkM
Boot Timer0 Leds
Interfaces
• Boot
• Timer
• Leds
• Coding conventions: TEP3
June 2008
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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();
}
June 2008
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BlinkM
Boot Timer0 Leds
?
?
?
Two Event Handlers
Each services
external event
by calling command
on some subsystem
14
Simple example: Boot interface
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();
}
•
•
•
•
$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.
June 2008
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Simple example: LEDs interface
#include "Leds.h"
interface Leds {
async command void
async command void
async command void
async command void
/*
* @param
*/
val
led0On();
led0Off();
led0Toggle();
led1On(); ...
a bitmask describing the on/off settings of the LEDs
async command uint8_t get();
async command void set(uint8_t val);
}
• $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
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Timer
interface Timer<precision_tag>
{
command void startPeriodic(uint32_t dt);
event void fired();
command void startOneShot(uint32_t dt);
command void stop();
command
command
command
command
command
command
command
bool isRunning();
bool isOneShot();
void startPeriodicAt(uint32_t t0, uint32_t dt);
void startOneShotAt(uint32_t t0, uint32_t dt);
uint32_t getNow();
uint32_t gett0();
uint32_t getdt();
}
•
•
$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
June 2008
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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 chipindependent.
• 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.
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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
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Timers
#include "Timer.h“
…
typedef struct { } TMilli; // 1024 ticks per second
typedef struct { } T32khz; // 32768 ticks per second
typedef struct { } TMicro; // 1048576 ticks per second
• Timers are a fundamental element of Embedded Systems
– Microcontrollers offer a wide range of different hardware features
– Idiosyncratic
• Logically Timers have
– Precision
– Width
– Accuracy
- unit of time the present
- # bits in the value
- 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
June 2008
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Example – multiple virtual timers
#include "Timer.h"
module Blink3M
{
uses interface Timer<TMilli>
uses interface Timer<TMilli>
uses interface Timer<TMilli>
uses interface Leds;
uses interface Boot;
}
implementation
{
event void Boot.booted()
{
call Timer0.startPeriodic(
call Timer1.startPeriodic(
call Timer2.startPeriodic(
}
as Timer0;
as Timer1;
as Timer2;
250 );
500 );
1000 );
event void Timer0.fired()
{
call Leds.led0Toggle();
}
event void Timer1.fired()
{
call Leds.led1Toggle();
}
event void Timer2.fired()
{
call Leds.led2Toggle();
}
}
June 2008
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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
June 2008
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Configuration
BlinkAppC
BlinkM
Boot Timer0 Leds
configuration BlinkAppC
Boot
{
MainC
}
implementation
{
components MainC, BlinkM, LedsC;
components new TimerMilliC() as Timer;
Timer
Leds
Timer
LedsC
BlinkM
-> MainC.Boot;
BlinkM.Leds
-> LedsC;
BlinkM.Timer0 -> Timer.Timer;
}
• 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.
June 2008
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A Different Configuration
BlinkC
BlinkM
configuration blinkC{
}
Boot Timer0 Leds
implementation{
components blinkM;
components MainC;
components Kernel;
Boot
blinkM.Boot -> Kernel.Boot;
blinkM.Leds -> Kernel.Leds;
components new TimerMilliC();
blinkM.Timer0 -> TimerMilliC.Timer;
Timer
TimerMillic
Leds
Kernel
}
• Same module configured to utilize a very different
system substrate.
June 2008
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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, wholesystem power management.
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Module state
module BlinkC {
uses interface Timer<TMilli> as Timer0;
uses interface Leds;
users interface Boot;
}
implementation
• Private scope
• Sharing through
explicit interface only!
– Concurrency, concurrency,
concurrency!
– Robustness, robustness,
robustness
{
uint8_t counter = 0;
event void Boot.booted()
{
call Timer0.startPeriodic( 250 );
• Static extent
• HW independent type
– unlike int, long, char
}
event void Timer0.fired()
{
counter++;
call Leds.set(counter);
}
}
June 2008
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TinyOS / NesC Platform Independent Types
• Common numeric types
• Bool, …
• Network Types
http://nescc.sourceforge.net
– Compiler does the grunt work to map to canonical form
June 2008
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Events
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()
• Call commands
• Signal events
• Provider of
interface handles
calls and signals
events
• User of interface
calls commands
and handles signals
Notify
{
Rollover
counter++;
call Leds.set(counter);
BlinkM
if (!counter) signal Rollover.notify(TRUE);
Boot Timer0 Leds
}
}
June 2008
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Examples - Event-Driven Execution
Web Server Application
Software
Service request
HTTP – application
protocol
Transport
recv
Kernel Fire
Data
Presentation
Network
Link
HplSignal
Phy
Hardware
June 2008
Radio
Flash
Timers
MCU
Drivers
Ports ADC
WEI L4 - TinyOS Prog
29
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!
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Examples
/* Power-hog Blocking Call */
if (send() == SUCCESS) {
sendCount++;
}
/* Programmed delay */
state = WAITING;
state = WAITING;
op1();
op1();
sleep(500);
/* Split-phase call */
// start phase
…
call send();
…
}
//completion phase
void sendDone(error_t err) {
if (err == SUCCESS) {
sendCount++;
}
}
call Timer.startOneShot(500);
command void Timer.fired() {
op2();
op2();
state = RUNNING
state = RUNNING;
June 2008
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Examples - Split-Phase
Web Server Application
Software
HTTP – application protocol
Data
Presentation
Transport
Kernel
Network
Link
HplSignal
Phy
Hardware
June 2008
Radio
Flash
Timers
MCU
Ports
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Drivers
ADC
32
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
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Read Interface
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 );
}
• Split-phase data acquisition of typed values
• Flow-control handshake between concurrent processed
– Hardware or software
• $tinyOS-2.x/tos/interface/read.nc
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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?
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Temp example configuration
configuration TempDispAppC {
}
implementation {
components SenseM, MainC, LedsC, new TimerMilliC() as Timer,
TempC ;
SenseM.Boot
SenseM.Leds
SenseM.Timer
SenseM.Read
->
->
->
->
MainC;
LedsC;
TimerMilliC;
TempC;
}
SenseM
TempDispAppC
Boot Read Timer0 Leds
MainC
June 2008
Boot
WEI L4 - TinyOS Prog
Read
Timer
Leds
TempC
Timer
LedsC
36
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
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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();
}
}
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Examples - Tasks
Web Server Application
serviceReq
notify
Software
HTTP – application protocol
Data
Presentation
Transport
Kernel
Network
Link
fired
HplSignal
Phy
Hardware
June 2008
Radio
fired
readDone
Flash
Timers
MCU
WEI L4 - TinyOS Prog
Ports
Drivers
ADC
39
Tasks
/* BAD TIMER EVENT HANDLER */
event void Timer0.fired() {
uint32_t i;
for (i = 0; i < 400001; i++) {
call Leds.led0Toggle();
• 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.
}
}
/* Better way to do a silly thing */
task void computeTask() {
Tasks
uint32_t i;
for (i = 0; i < 400001; i++) {}
event
s
}
event void Timer0.fired() {
commands
call Leds.led0Toggle();
post computeTask();
Interrupts
}
Hardware
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Uses of tasks (???)
•
•
•
•
•
•
•
June 2008
High speed sampling
Filtering
Queueing
Smoothing
Detection
Classification
…
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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
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Canonical SensorNet Network Architecture
Patch
Network
Sensor Node
Sensor Node
Sensor Patch
Gateway
Gateway
Transit Network
(IP or not)
Access point
- Base station
- Proxy
Client Data Browsing
and Processing
Intranet/Internet (IP)
Verification
links
Other information
sources
Data Service
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Typical IP Network
Internet
VPN
tunnels
External networks
ISP
Company Router / Firewall
Internal Private networks
externally
accessible hosts
ethernet
internally
accessible hosts
DMZ
WiFi
Stand-alone networks
WiFI
serial lines
leased links
point-point links
inaccessible
hosts
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TinyOS 2x Embedded IP Architecture
Higher Level Embedded Web Services
IP route L3
SPI, i2c,
arbiters
UART
June 2008
Virtual
ms Timer
Low-Power
802.15.4
Flash
Storage
IP 6LowPAN L2
OTA
s
Timer
RTC
Basic
Configuration
Services
Pwr Mgr
Basic Health &
Mgmt Services
Scheduler
UDP/TCP L4
Ext.
INT
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Sensor
Drivers
GPIO
Pins
ADC
45
WSNs in an IP context
Internet
Internet
IP-based
corporate
networks
IP-based
corporate
networks
gateway
computer
controllers
& analytics
ad hoc
embedded
network
IP-based
embedded
network
ad hoc
embedded
network
monitoring devices
IP-based
embedded
network
monitoring devices
Stand-alone embedded networks
June 2008
Router /
Firewall
controllers
& analytics
Internally connected embedded networks
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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
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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
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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 ???
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UDP Interface
interface
command
command
command
Udp {
error_t bind( uint16_t port );
uint16_t getMaxPayloadLength( const sockaddr_in6_t *to );
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 );
}
• 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
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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…
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TCP Interface
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();
}
• Transitions of the TCP protocol reflected as events
• Recv per segment
• Send is NOT SPLIT PHASE !!!
– More on this later
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Example TinyOS Service Architecture
Hardware
Abstraction
Layer
Other
Sounder
Light
RF
Discovery
Events
Attributes
Commands
Messages
Network
Volumes
Links
Buses & ADCs
Flash
Radio / Uart
Sensor/Actuator
Management & Pwr
Basic OS
interface
Blocks
Logs
Files
Service
API
OTA program
Application
Hardware
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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
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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, …
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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.
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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
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On boot – Mount and Read
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Config data – done, write, commit
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Network Embedded Systems
Hardware
Abstraction
Layer
Other
Sounder
Light
RF
Discovery
Events
Attributes
Commands
Messages
Network
Volumes
Links
Buses & ADCs
Flash
Radio / Uart
Sensor/Actuator
Management & Pwr
Basic OS
interface
Blocks
Logs
Files
Service
API
OTA program
Application
Hardware
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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;
}
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TinyOS IPv6 Network Kernel
• Network Kernel
– Manages communication and storage
– Scheduler (decides when to signal events)
Application
IPv6 Network Kernel
Radio
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Timer
Flash
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Driver
Driver
Driver
Driver
Driver
Driver
Sensors
Sensors
Sensor
Actuator
Actuator
Actuator
62
Network Embedded Systems
Hardware
Abstraction
Layer
Our kernel
boundary
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Other
Sounder
Light
RF
netstat
Echo
ICMP / UDP / TCP
6LoWPAN Network
Volumes
Links
Buses & ADCs
Flash
Radio / Uart
Sensor/Actuator
Management & Pwr
Basic OS
interface
OTA
Blocks
Logs
Config
Service
API
Systat
Application
Hardware
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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
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Discussion
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Traditional TinyOS Active Messages
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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
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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.
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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.
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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.
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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.
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tos/types/message.h.
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;
• Link level concept used throughout the TinyOS
research community and industry.
• How does this move forward to IP/WSN?
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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;
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event void Boot.booted() {
call AMControl.start();
}
event void AMControl.startDone(error_t err) {
if (err == SUCCESS) {
call Timer0.startPeriodic(TIMER_PERIOD_MILLI);
}
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}
73
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;
}
}
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Receive – a network event
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;
• Service the incoming message
} BlinkToRadioMsg;
– 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.
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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.
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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;
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Indexed interfaces for dispatch
SVC x
SVC y
SVC z
SVC w
Active Message
Network Stack Implementation
Hardware
• Clients & Applications have individual view
• Provider has global view
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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
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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
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Wiring Examples ???
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