Wireless Sensor Networks Introduction to the Laboratory

Chiara BurattiDEI, University of Bologna

Wireless Sensor Networks

Introduction to the Laboratory

Chiara Buratti

c.buratti@unibo.it+39 051 20 93147

Office Hours: Tuesday 3 – 5 pm @ Main Building, third floor

Credits: 6

Outline

• MC1322x Devices

• IAR Embedded workbench / Beekit

• Basics of Network Software

• Freescale 802.15.4 Software

• Embedded C

Outline

• MC1322x Devices

• Embedded C

Freescale MC1322x Transceiver

• 16 Channels in the 2.4 GHz ISM band

• Transmit Power -30 dBm to +4 dBm typical

• Supports 250 kbps bit rate

• RX sensitivity of -96 dBm (Typical) at 1.0% Packet Error Rate (20 Bytes packets)

Freescale MC1322x Transceiver

Current consumption:

• — 22 mA typical RX current draw (DCD mode) with radio and MCU active

• — 29 mA typical TX current draw with radio and MCU active (coin cell capable)

• — 3.3 mA typical current draw with MCU active (radio off)

• — 0.8 mA typical current with MCU idle (radio off)

• — 0.85 μA typical Hibernate current

(retain 8 Kbyte SRAM contents)

• — 0.4 μA maximum Off current

(device in reset)

Turnaround times:

• IEEE 802.15.4 requires a TX-to-RX or a

RX-to-TX TaT ≤ 12 Ts (192 μs).

• 11 Ts (176 μs) RX-to-TX

• 96 μs TX-to-RX.

Freescale MC1322x MCU

• 32-bit ARM7 CPU

• 128 Kbytes FLASH Memory, 96 Kbyte SRAM, 80 Kbyte ROM

• Dedicated 802.15.4 modem/radio interface module (RIF)

• Up to 64 programmable I/O

• Two serial communications interface modules (UART)

• Serial peripheral interface module (SPI)

MC1322x Block Diagram

Transceiver

MAC Accelerator Block Diagram

MACA core main features include:

• Acknowledgement transmission / reception

• Generate MAC data.request / reply to MAC data.request

• Dedicated DMA for transfer of TX/RX data from/to RAM

• Frame manager

— Handles preamble data

— Handles frame check sequence (FCS) using CRC

— Embedded header filter for received packets

MAC Accelerator Block Diagram

Outline

• MC1322x Devices

• Embedded C

IAR / BeekitBeeKit:

A useful tool to create IAR

projects

IAR Embedded WorkbenchIntegrated Development

Environment (IDE) for MC1322x

Freescale Platform

IAR - Project

Outline

• MC1322x Devices

• Embedded C

Basics on Service Primitives

• Services of a layer are the capabilities it offers to the user in the next upper layer: Level n is a service provider for layer n+1, while layer n+1 is a service user for layer n.

• Services are described through the information flow between layers modeled through discrete events: each event consists of passing aservice primitive from one layer to another through Service Access Points (SAP).

Basics on Service Primitives: Vertical view

request confirm

Service user for MAC Layer

Service user for PHY Layer

Service provider for APP Layer

Service provider for MAC Layer

Basics on Service Primitives: Horizontal view

Basics on Service Primitives

Primitive Meaning

requestan entity is requesting a service

(we are requesting a connection to a remote computer)

indicationan entity is informed of an event

(the receiver has just received a connection request)

responsean entity is responding to an event

(the receiver is sending the permission to connect)

confirm

an entity acknowledges the response to its request

(the sender acknoledge the permission to connect to the remote host)

Service Primitives: an Example

Outline

• MC1322x Devices

• Embedded C

Freescale MAC/PHY Software

Vertical

Horizontal

• MLME interface: all MAC command

• MCPS interface: data primitive

• ASP interface: various application

support features

Interfacing APP to MAC

• The interface between APP and MAC layers is based on service primitives passed as messages from one layer to another.

• Messages are sent to a SAP function which is responsible for handling the message.

• Five SAPs exist:

– NWN_MLME_SapHandler()

– NWK_MCPS_SapHandler()

– MLME_NWK_SapHandler()

– MCPS_NWK_SapHandler()

– APS_APP_SapHandler()

• Arrows Messages

Interfacing APP to MAC

MAC API

• MAC Application Programming Interface (API) provides a simple way of interfacing to the Freescale MAC SW.

• The API functions available are used for:

– Initializing the MAC

– Running the MAC

– Allocating messages

– Deallocating messages

– Sending messages

– Queueing and dequeueing messages

MAC API Functions

MAC API - Messages

In order to request a service the Application must:

1. Allocate the message;2. Fill the message parameters

3. Send the message to the SAP Handler.

MAC API – Queueing

MAC API – Data Types

Message Types: NWK-to-MLME directionmlmeMessage_t

Message Types: MLME-to-NWK directionnwkMessage_t

Message Types: NWK-to-MCPS directionmcpsMessage_t

Message Types: MCPS-to-NWK directionmcpsToNwkMessage_t

AppTask

- Your code generally goes here

- It is called by task scheduler if an

event happens

Coordinator Finite State Machine

InitScanED

ScanEDWait

Confirm

Start CoordWait Confirm

Start Coord

Listen

gAppEvtRxFromUart_c

gAppEvtMessageFromMLME_c

gAppEvtMessageFromMCPS_c

gAppEvtDummyEvent_c gAppEvtStartCoordinator_c

gAppEvtDummyEvent_c

To generate a dummy event call:

TS_SendEvent(gAppTaskID_c, gAppEvtDummyEvent_c);

End Device Finite State Machine

InitScan

Active

ScanActiveWait

Confirm

Associate Wait Confirm

Associate

Listen

gAppEvtRxFromUart_c

gAppEvtMessageFromMCPS_c

gAppEvtDummyEvent_c

To generate a dummy event call:

TS_SendEvent(gAppTaskID_c, gAppEvtDummyEvent_c);

MLME and MCPS Interfaces

• When requesting a service that is asynchronous, the MLME (or MCPS) must deallocate the message.

• SAP Handler only queue the message and returns asap.

• An event needs to be passed to the application task in order to notify that a new message from the MLME (or MCPS) has arrived from MLME_NWK (or MCPS_NKW).

MLME_NWK SAP Handler

MCPS_NWK SAP Handler

Outline

• MC1322x Devices

• Embedded C

Standard Input / Output

• In the world of microcontrollers, there is no environment that provides standard IO. Unlike ANSI C, there is no printf() function that prints formatted strings to the default output and no scanf() function that reads formatted strings from standard input.

• In Freescale 802.15.4 MAC Stack:

• Sending strings to the serial port:

void UartUtil_Print(uint8_t* pString, uartUtilBlock_t allowToBlock)

allowToBlock: gNoBlock_d, gAllowToBlock_d

• Sending hex data to serial port:

void UartUtil_PrintHex(uint8_t* hex, uint8_t len, uint8_t flags)

flags: gPrtHexBigEndian_c, gPrtHexNewLine_c , gPrtHexCommas_c, PrtHexSpaces_c

Standard Input / Output: Examples

• Example 1:

UartUtil_Print("\n\rStarting as PAN coordinator on channel 0x", gAllowToBlock_d);

UartUtil_PrintHex(&mLogicalChannel, 1, FALSE);

• Example 2:

UartUtil_Print("ED scan returned the following results:\n\r [", gAllowToBlock_d);

UartUtil_PrintHex(pEdList, 16, gPrtHexBigEndian_c | gPrtHexSpaces_c);

UartUtil_Print("]\n\r\n\r", gAllowToBlock_d);

• Example 3:

UartUtil_Tx(pMsgIn->msgData.dataInd.pMsdu, pMsgIn->msgData.dataInd.msduLength);

UartUtil_Print(" ",gAllowToBlock_d);

UartUtil_PrintHex(&pMsgIn->msgData.dataInd.mpduLinkQuality,1, gPrtHexBigEndian_c | gPrtHexNewLine_c);

UartUtil_Print("\n\r",gAllowToBlock_d);

Data Types and Variables

Due to the restricted environment of embedded controllers, standard C variables and data

types are different.

In Freescale 802.15.4 MAC Library:

int8_t signed char

uint8_t unsigned char

int16_t signed short

uint16_t unsigned short

int32_t signed long

uint32_t unsigned long

Types Definitions

Syntax:

typedef existing-type new-type ;

Example:

typedef signed short int16_t;

typedef unsigned short uint16_t;

typedef signed char int8_t;

typedef unsigned char uint8_t;

typedef signed long int32_t;

typedef unsigned long uint32_t;

Structures

Definition:

//PAN descriptor. Used, e.g., in Scan Confirm

typedef struct panDescriptor_tag {

uint8_t coordAddress[8];

uint8_t coordPanId[2];

uint8_t coordAddrMode;

uint8_t logicalChannel;

bool_t securityUse;

uint8_t aclEntry;

int8_t securityFailure;

uint8_t superFrameSpec[2];

bool_t gtsPermit;

uint8_t linkQuality;

uint8_t timeStamp[3];

} panDescriptor_t;

Usage:

panDescriptor_t.logicalChannel

(&panDescriptor_t)->logicalChannel

EnumeratorsDefinition:

/* The various states of the applications state

machines. */

enum {

stateInit,

stateScanEdStart,

stateScanEdWaitConfirm,

stateStartCoordinator,

stateStartCoordinatorWaitConfirm,

stateListen

/* Error codes */

enum {

errorNoError,

errorWrongConfirm,

errorNotSuccessful,

errorNoMessage,

errorAllocFailed,

errorInvalidParameter,

errorNoScanResults

Usage:

uint8_t gState;

switch(gState)

case stateInit:

//do something

break;

case stateScanActiveStart:

//do something

break;

Bitwise Operators

Operator name Syntax

Bitwise left shift a << b

Bitwise right shift a >> b

Bitwise one's complement (NOT) ~a

Bitwise AND a & b

Bitwise OR a | b

Bitwise Operators - Shift

Examples:

0000 0001 << 1 gives 0000 0010

0000 0010 << 1 gives 0000 0100

0000 0100 >> 1 gives 0000 0010

/* Events that are passed to the application task.

Are defined as byte masks to make possible

send multiple events to the task */

#define gAppEvtDummyEvent_c (1 << 0) //first bit

#define gAppEvtRxFromUart_c (1 << 1) //second bit

#define gAppEvtMessageFromMLME_c (1 << 2)

#define gAppEvtMessageFromMCPS_c (1 << 3)

#define gAppEvtStartCoordinator_c (1 << 4)

Bitwise Operators – AND / OR

Bitwise AND operator

unsigned int a = 6; /* 6 = 0000 0110 */

unsigned int b = 3; /* 3 = 0000 0011 */

unsigned int c = 0;

c = a & b; /* 2= 0000 0010 */

Bitwise OR operator

unsigned int a = 6; /* 6 = 0000 0110 */

unsigned int b = 3; /* 3 = 0000 0011 */

unsigned int c = 0;

c = a I b; /* 7= 0000 0111 */

Laboratory Material

• You can find on the website www.chiaraburatti.org the following meterial:

– Data Sheets of MC1322x Devices

– Freescale 802.15.4 Software Reference manual

– Laboratory Handbook

– This presentation

• Devices are available under request

• Virtual machine including all the needed SW is available under request

Chiara Buratti

www.chiaraburatti.org

c.buratti@unibo.it

Wireless Sensor Networks Introduction to the Laboratory

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