Network Reprogramming

Jaein Jeong, Sukun Kim

Nest Meeting

July 30, 2003

Concept

• Parallel programming– A mote is loaded program with direct connection

• Network programming– The program code is stored outside the program

memory through radio packets.

– Downloaded code is transferred to the program memory afterwards.

PC

ProgramMemory

Mote

ProgramCode

Parallel programming.

Base Station

EEPROM

Mote

ProgramCode

PC

ProgramMemory

Network programming

Components

• On motes– XnpM module handles most of the jobs.– Main application needs to be wired to XnpC.

• On PC– Xnp java program sends program code through radio.

• Message Formats– AMID: set to #47.– CMD: type of command (e.g., download, query and etc).– PID: Checksum for program code. Used for validation– CID: Sequence number for capsule

PC

Xnp javaApp XnpC

Mote Radiopackets

5 6 7:8

CMD SUBCMD PID CID Data

9:10 11:end0:1

Dest AMID

2

GID

3

Len

4

Steps of network programming

• Download Phase

• Query Phase

• Reprogram Phase

Download Phase

• Start of download– Xnp java program sends a request and XnpM relays this reque

st to the main module.

– Main module can reserve resources and acknowledges to XnpM.

– ‘Download start’ message is sent multiple times.

Xnp javaprogram

XnpMmodule

Mainmodule

(1) Download start(2) Download request event

(3) accept/deny by replying

• Download– java program sends each line of program as a capsule.

– The capsule is stored in EEPROM by XnpM.

Query Phase

• A mote gets any missing capsules in query loop.1. java program asks motes for missing capsules.

2. Each mote scans EEPROM and requests the retransmission of the next missing capsule.

3. In response, java program sends the missing capsule.

4. Other motes can also fill the hole as well as the requestor.

• Query loop ends when the java program doesn’t get request for several times.

Xnp javaprogram

Mote 1 (1) Query for missing capsule

Mote 3

Mote 2 (2) Request for retransmission

(3) Retransmission of capsule

(2) Scan(4) Fill the hole

Reprogram Phase

• The downloaded code is transferred to the program memory and the mote starts the new program.

– First, java program sends a reprogram request.

– After checking the EEPROM for correctness, XnpM transfers control to the boot loader.

– The boot loader copies the code in EEPROM to program memory and reboots the system.

• After reboot, mote ID and group ID needs to set correctly.

Protocol

PC

Mote

Start CompleteDownload

Start CompleteReady for Download

Download Phase

Query

1 2 3 4 5 6 7 34 35 368 33. . .

1 2 3 4 5 6 7 34 35 368 33. . .

1 2 3 4 5 6 7 34 35 368 33. . .

Mote 1

Mote 2

Mote 3

PC

Query PhaseService 2

Hole

Query Service 3

Hole

Query Service 1 Query

TimeoutCompleted !!!

Hole

More detail in Phase 2

Query to all

1 2 3 4 5 6 7 34 35 368 33. . .Mote 2

PC

Query PhaseService 2

Hole

Hole 2

Once

Query to 2

Next Hole

Hole 7

Once

Query to 2 Hole 7

Once

Again

EEPROM write failure

Query to 2

Again

Hole 7

Once

Query to 2

Next Hole

Query to all

Quit ‘Service 2’

Modification

PC

Mote

Start CompleteDownload

Start Complete

Download Phase

Query

1 2 3 4 5 6 7 34 35 368 33. . .

1 2 3 4 5 6 7 34 35 368 33. . .

1 2 3 4 5 6 7 34 35 368 33. . .

Mote 1

Mote 2

Mote 3

PC

Query PhaseService 2 Query Service 3 Query Service 1 Query

Failure !!!

Or

Or

Increase the number ofcontrol message retransmission

Modification (continued)

PC

Mote

Start CompleteDownload

Start CompleteReady for Download

Download Phase

Query

1 2 3 4 5 6 7 34 35 368 33. . .

1 2 3 4 5 6 7 34 35 368 33. . .

1 2 3 4 5 6 7 34 35 368 33. . .

Mote 1

Mote 2

Mote 3

PC

Query PhaseService 1

Hole

Query Service 3 Query

Timeout Failure !!!Completed

Increase query timeout

Modification (continued)

Query to all

1 2 3 4 5 6 7 34 35 368 33. . .Mote 2

PC

Query PhaseService 2

Hole

Hole 2

Once

Query to 2

Next Hole

Hole 7

Once

Query to 2 Hole 7

Once

Again

EEPROM write failure

Query to 2

Again

Hole 7

Once

Query to 2

Next Hole

Query to all

Eliminate timeout using positive ack

Quit ‘Service 2’

How to wire apps for network programming• In configuration file (AppC), XnpC module should be connec

ted to the implementation (AppM).

• In AppM, two events should be handled.

XnpCAppM.Xnp

AppC

XnpMmodule

AppMmodule

Xnp.NPX_DOWNLOAD_REQ

Xnp.NPX_DOWNLOAD_ACK

XnpMmodule

AppMmodule

Xnp.NPX_DOWNLOAD_DONE

Start download event

Terminate download event

Location of Network programming module• Check out these directories in CVS.

– Tinyos-1.x/apps» XnpService: main module for network programming

.

» XnpCount: a sample app

» XnpRfmToLeds: a sample app

– Tinyos-1.x/tools/java/net/tinyos» Util_xbow: a modification to SerialStub

» Xnp: xnp java program

Installing network programmable code• A network programmable code should be loade

d using parallel programming in the beginning.1. Compile an application in ATmega128 native.

– Currently, supported in mica2, mica2dot.– Latest tool: avr-gcc, nesC 1.1 and uisp needed.– Refer to http://webs.cs.berkeley.edu/tos/mica2.html

2. Load app binary in ATmega128 native mode.uisp -dprog=dapa --wr_fuse_e=ff -–eraseuisp -dprog=dapa -–wr_fuse_e=ff -–upload if=main.srecuisp -dprog=dapa -–wr_fuse_e=ff -–verify if=main.srec

3. Load boot loader.uisp –dprog=dapa --upload if=bootloader.srec

Issues in PC side.

• Xnp java program– sends a command, a program capsule and hears the res

ponse from the motes.– sends/receives radio packets through UART.

• Different versions of GenericBase.– GenericBase

» Easy to lose sync. Not recommended for network programming.

– Sync GenericBase» Check sync bytes of UART packet. Works for both direct a

ccess and SerialForward– XGenericBase

» Check sync bytes of UART packet. Only works for direct access

• Sync GenericBase with SerialForward is recommended.

Test Results

Num Motes

Num Tries

Download Time (s)

Query Time (s)

Num Successes

4 4 106 24.25 4

8 4 106 72.25 7.75

16 4 106 63 16

• Test program: XnpCount– Program size: 37000 bytes, 841 capsules.

0

50

100

150

200

250

300

4 4 4 4 8 8 8 8 16 16 16 16

Num Motes

Query Time (sec)

Download Time (sec)

Test Results (Cont.)• We could get reasonable success rate when mote

s are normal.• Cases when network programming fails.

– Parameters in xnp java is not correct.» When xnp sends packets faster than GenericBase can han

dle.» This can halt network programming globally.» Interval between each write should be large enough for Ge

nericBase to handle. 120 ms was found by experiment.– Program code is not correctly loaded initially.

» Mote doesn’t go into download mote.– A mote cannot write into its EEPROM.

» This happened when battery voltage was low. And was fixed with new battery.

– After hardware modification was made.» A mote didn’t work properly when we solder the loose batt

ery connection.» We needed to load the code with parallel programming.

Discussion• Can we assume that program image is correct

just by checking PID and CID are correct?• When mote #1 loses packet K, does its neighbor

mote #2 also lose the packet?• Experiments showed that query time increases

with the number of motes. Will it be worthwhile to use Forward Error Correction (FEC) for larger number of motes?

• Does network programming justify the higher power consumption in favor of convenience?

• May need characteristic numbers about motes and TinyOS– Radio Speed, Packet loss rate– EEPROM Speed (read, write), write failure rate– Atomicity of EEPROM write