David Culler, Jason Hill, Robert Szewczyk, Alec WooU.C. Berkeley2/9/2001

TinyOS Programming Boot Camp

Part II – Tiny OS Component Design and Tools

2-9-2001 TOS Boot 2 2

Networked Sensor System Challenge

• Managing multiple concurrent flows– some with real-time requirements

• Very limited I/O controller hierarchy– process every bit, or perhaps byte in CPU

• Asynchronous and synchronous devices• Limited storage and processing• At very low power

sensorsactuators

network

storage

2-9-2001 TOS Boot 2 3

TinyOS Execution Contexts

Hardware

Interrupts

eve

nts

commands

Tasks

2-9-2001 TOS Boot 2 4

TinyOS Storage Model

• Single shared stack

• Each component has a static frame– only accessible locally (except msg buffers)

• Msg buffers allocated statically by components, but shared dynamically by ownership discipline

2-9-2001 TOS Boot 2 5

TinyOS Commands and Events

{... status = TOS_CALL_COMMAND(name)(args)...}

TOS_COMMAND(name)(args) {...return status;}

{... status = TOS_SIGNAL_EVENT(name)(args)...}

TOS_EVENT(name)(args) {...return status;}

2-9-2001 TOS Boot 2 6

Commands

• Function call across component boundary– cause action to be initiated

– bounded amount of work

» cannot block

– always return status (0 => error)

» component can refuse to perform command

• share call stack and execution context

• command body has access to local frame

• commands may post tasks or call commands

• commands may not signal events

2-9-2001 TOS Boot 2 7

Events

• Upcall to notify action has occured– must do bounded (and small) amount of work– cannot block– access local frame, shares stack

• Lowest-level events triggered by hardware interrupts– hardware abstraction components perform critical section

and enable interrupts

• Events may signal events• Events may call commands

• Entire event “fountain” must stay within overall application jitter tolerance

2-9-2001 TOS Boot 2 8

FSM Programming Style

• Most components are essentially FSMs

• Composed via events and commands

• non-blocking!

sens_output_init

initc

sens_output_start

startc

/sub_clock_init

/sub_output_init

sens_clock_event

clocke

/getdata

sens_data_ready

datae

/output

clocke

2-9-2001 TOS Boot 2 9

TASKS

• provide concurrency internal to a component– longer running operations

• are preempted by events

• able to perform operations beyond event context

• may call commands

• may signal events

• not preempted by tasks

{...TOS_POST_TASK(name)...}

void TOS_TASK(name) {...}

2-9-2001 TOS Boot 2 11

Typical application use of tasks

• event driven data acquisition

• schedule task to do computational portion

char TOS_EVENT(MAGS_DATA_EVENT)(int data){

struct adc_packet* pack = (struct adc_packet*)(VAR(msg).data);

printf("data_event\n");

VAR(reading) = data;

TOS_POST_TASK(FILTER_DATA);

...

mags.c

2-9-2001 TOS Boot 2 12

Filter Magnetometer Data Task

TOS_TASK(FILTER_DATA){

int tmp;

VAR(first) = VAR(first) - (VAR(first) >> 5);

VAR(first) += VAR(reading);

VAR(second) = VAR(second) - (VAR(second) >> 5);

VAR(second) += VAR(first) >> 5;

VAR(diff) = VAR(diff) - (VAR(diff) >> 5);

tmp = VAR(first) - VAR(second);

if(tmp < 0) tmp = -tmp;

VAR(diff) += tmp;

if((VAR(diff) >> 5) > 85){

TOS_CALL_COMMAND(MAGS_LEDg_on)();

VAR(led_on) = 255;

}

}

2-9-2001 TOS Boot 2 13

Tasks in low-level operation

• transmit packet– send command schedules task to calculate CRC– task initiated byte-level datapump– events keep the pump flowing

• receive packet– receive event schedules task to check CRC– task signals packet ready if OK

• byte-level tx/rx– task scheduled to encode/decode each complete byte– must take less time that byte data transfer

• i2c component– i2c bus has long suspensive operations– tasks used to create split-phase interface– events can procede during bus transactions

2-9-2001 TOS Boot 2 14

High-level use of tasks

• virtual machine interpreter schedules an “interpretation task” on clock event– similar for data event

• may be a long running activity

• utilizes many low-level components

• reschedules itself on each virtual machine instruction

2-9-2001 TOS Boot 2 15

Scheduling

• current sched.c is simple fifo scheduler

• Bounded number of pending tasks

• When idle, shuts down node except clock

• Uses non-blocking task queue data structure

2-9-2001 TOS Boot 2 16

Programming tools

2-9-2001 TOS Boot 2 17

TOS compile time tools

• tools/desc2objs– Generates the list of components that need to be compiled

into an application

– Generates “C” header files from .comp files

• tools/mkheader

• tools/mksuper_desc– Generates the super.h linkage file that wires components

together

• tools/mk_amdisp– Generates the mappings between handler ID’s and handler

function names for the AM_MSG macro

2-9-2001 TOS Boot 2 18

tools/mkheader

• Generates “C” header files from .comp files

• Usage:mkheader component_file

• Example: ./tools/mkheader APP.comp > APP.h

• Looks for ACCEPTS, USES, SIGNALS, HANDLES section of comp files.

2-9-2001 TOS Boot 2 19

tools/desc2objs

• Generates the list of components that need to be compiled into an application

• Walks the graph of description files to determine which components are used by the application

• Looks at .comp files for IMPLEMENTED_BY directives

• Usage:– Desc2objs description_file

• Example:– ./tools/desc2objs apps/cnt_to_leds.desc > Makefile.objs

• Output:CUST_OBJS = MAGS.o system/ADC.o system/AM.o system/CLOCK.o system/LEDS.o

system/MAIN.o system/PACKETOBJ.o system/RFM.o system/SEC_DED_RADIO_BYTE.oHEADER_FILES = MAGS.h system/ADC.h system/AM.h system/CLOCK.h system/LEDS.h

system/MAIN.h system/PACKETOBJ.h system/RFM.h system/SEC_DED_RADIO_BYTE.h

2-9-2001 TOS Boot 2 20

tools/mksuper_desc

• Generates the super.h linkage file that wires components together

• Walks the graph of description files to determine which components are used by the application

• Looks at .comp files for IMPLEMENTED_BY directives and types for each function.

• Automatically generates fan-out code based on number and types of connections to each net.

• Wires components together with #define.

• Usage: mksuper_desc description_file...

2-9-2001 TOS Boot 2 21

tools/mksuper_desc (cont.)

• Treats all of the wiring lines from all the description files together.

• Example Description file excerpt:GENERIC_COMM:COMM_SEND_MSG_COMMAND AM:AM_SEND_MSGCHIRP:CHIRP_SEND_MSG GENERIC_COMM:COMM_SEND_MSG

• Example Output:#define COMM_SEND_MSG_COMMAND AM_SEND_MSG_COMMAND#define CHIRP_SEND_MSG_COMMAND AM_SEND_MSG_COMMAND#define AM_MSG_HANDLER_4_EVENT INT_READING_EVENT

2-9-2001 TOS Boot 2 22

tools/mk_amdisp

• Generates the mappings between handler ID’s and handler function names for the AM_MSG macro

• Sends AM_DISPATCH.mapping through C preprocessor and determines the function names of the active message types that are being handled.

• Inserts macros that map from function name to handler number into am_dispatch.h

• Usage:mk_amdisp

• Output:#define INT_READING_EVENT__AM_DISPATCH 4 INT_READING_EVENT is handles message type 4.

2-9-2001 TOS Boot 2 23

All_headers.c

• Used to type check across all of the component descriptions.

• Compiled into a “.o” but not linked.

• Will reveal errors that arise from:– Wiring the wrong functions together

– Connecting incompatible components together

– Mistakes in .comp files

2-9-2001 TOS Boot 2 24

Listen and Inject

• tools/listen.* & tools/inject.*– Reads from the serial port and prints out packets to the

screen

• Linux uses .c or .java versions, Windows uses .java versions

• Listen reads in packets from the UART and prints them out.

• Inject sends out a single packet out the UART and then proceeds to print out data that is returned.

2-9-2001 TOS Boot 2 25

MakefilePC

• You can compile TinyOS code to run on a PC

• Used as a debugging tool

• Verify application logic and state machine transitions before running code on Mote

• Trust me, it’s worth taking the time to run it on the PC!!!

• Can even debug networking applications

2-9-2001 TOS Boot 2 26

Project: build a component

• Build a few nodes as sens_to_rfm to serve as data sources

• Build generic_base to forward all traffic it picks up to the host

• Using rfm_to_led as a starting point, construct a new application that will aggregate sensor readings and forward min,avg,max to the host– new AGGREGATE.comp and AGGREGATE.c

» int reading handler might build a table of neighbor values

» on change or tick, post task to compute aggregate and send new active message with aggregate

– new agg.desc