1. A System Architecture for Tiny Networked Devices
Jason Hill
U.C. Berkeley
9/22/2000

2. Who We Are: The Tiny OS Group
Jason Hill – CS Grad Student
Robert Szewczyk – CS Grad Student
Alec Woo – CS Grad Student
Seth Hollar – EE Grad Student
David Culler (Prof.)
Kris Pister (Prof.)

3. Goals:
To develop an ultra low power networked sensor platform, including hardware and software, that enables low-cost deployment of sensor networks.
To be a system level bridge that combines advances in low power RF technology with MEMS transducer technology.

4. Key Characteristics of TNDs
Small physical size and low power consumption
=> Limited Physical Parallelism and Controller Hierarchy
=> primitive direct-to-device interface
Concurrency-intensive operation
flow-thru, not wait-command-respond
=> must handle multiple inputs and outputs simultaneously
Diverse in Design and Usage
application specific, not general purpose
huge device variation
=> efficient modularity
=> migration across HW/SW boundary
Largely Unattended & Numerous
=> robust operation
=> narrow interfaces

5. ‘Mote’–The Hardware COTS Dust weC Mote 4Mhz, 8bit MCU (ATMEL)
512 bytes RAM, 8K ROM
900Mhz Radio (RF Monolithics)
ft. range
Temperature Sensor
Light Sensor
LED outputs
Serial Port

6. Tiny OS – The Software
Provides a component based model abstracting hardware specifics from application programmer
Utilizes an event based programming model to allow high levels of concurrency
Allows multiple applications to be “running”
Services Provided Include:
Active Messages Based messaging protocol
Periodic Timer Events
Asynchronous access to UART data transfers
Mechanism for Static, Persistent Storage
Can “Swap Out” system components to get necessary functionality.
Complete applications fit in 4KB of ROM and 256B RAM.

7. Second Generation ‘Mote’
Two Board Sandwich
Main CPU board with Radio Communication
Secondary Sensor Board
Allows for expansion and customization
Current sensors include: Acceleration, Magnetic Field, Temperature, Pressure, Humidity, Light, and RF Signal Strength.
Can control RF transmission strength

8. Multi-Hop Routing Demo
Sensors automatically assemble and determine routing topology
Parallel Breadth First Search
Shortest path to all nodes remembered
Base station broadcasts out routing information
Individuals listen for and propagate route update
N messages sent
Generational scheme to prevent cycles in routing table
Base

9. Demo (cont.) Sensor information propagated up routing tree
Statistics kept for number of readings received and number of packets forwarded by each node
Sensors transmit data when “significant” events occur or when time limit is exceeded
Must be continuously listening for packets to be forwarded – impacts power considerations

10. Short Term Goals: Deploy sensor net in Soda for week long trial runs
Amass a collection of hundreds of first generation nodes
Improve Radio communication reliability
Bring online second generation hardware
Target Civil Engineering’s and The Center For the Built Environment’s needs to get a real world deployment.
Support applications where data is “picked up” by UAV’s

11. Tiny OS Internals Scheduler and Graph of Components
constrained two-level scheduling model: tasks + events
Component:
Frame (storage)
Tasks (concurrency)
Commands, and Handlers (events)
Constrained Storage Model
frame per component, shared stack, no heap
Very lean multithreading
Layering
components issue commands to lower-level components
event signal high-level events, or call lower-level commands
Guarantees no cycles in call chain

12. TOS Component /* Messaging Component Declaration */ //ACCEPTS:
init
Power(mode)
TX_packet(buf)
TX_packet_done (success)
RX_packet_done (buffer)
Internal State
power(mode)
send_msg(addr, type, data)
msg_rec(type, data)
msg_send_done (success)
send_msg_thread
/* Messaging Component Declaration */
//ACCEPTS:
char TOS_COMMAND(AM_SEND_MSG)(char addr,char type, char* data);
void TOS_COMMAND(AM_POWER)(char mode);
char TOS_COMMAND(AM_INIT)();
//SIGNALS:
char AM_MSG_REC(char type, char* data);
char AM_MSG_SEND_DONE(char success);
//HANDLES:
char AM_TX_PACKET_DONE(char success);
char AM_RX_PACKET_DONE(char* packet);
//USES:
char TOS_COMMAND(AM_SUB_TX_PACKET)(char* data);
void TOS_COMMAND(AM_SUB_POWER)(char mode);
char TOS_COMMAND(AM_SUB_INIT)();

13. Event Based Prog. Model System composed of state machines
Each State Machine is a TinyOS “component”
Command and event handlers transition a component from one state to another
Quick, low overhead, non-blocking state transmissions
Allows many independent components to share a single execution context
Emerging as design paradigm for large scale systems
“Tasks” are used to perform computational work
Run to completion, Atomic with respect to each other

14. Composition to Complete Application
Route map
router
sensor appln
application
Active Messages
packet
Radio Packet
Serial Packet
Temp SW
byte
UART HW
Radio byte
i2c
photo
bit
RFM
clocks