book

Getting Started with Bluetooth Low Energy

by Kevin Townsend, Carles Cufí, Akiba, Robert Davidson

April 2014

Beginner to intermediate

180 pages

4h 42m

English

O'Reilly Media, Inc.

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Who This Book Is ForHow to Use This BookOverview of BLETools for Development and TestingDevelopment PlatformsConventions Used in This BookUsing Code ExamplesSafari® Books OnlineHow to Contact UsAcknowledgments
What Makes BLE DifferentThe SpecificationConfigurationsBased on Specification SupportBased on Chip CountKey LimitationsData ThroughputOperating RangeNetwork TopologyBroadcasting and ObservingConnectionsProtocols versus ProfilesGeneric ProfilesUse-Case-Specific ProfilesSIG-defined GATT-based profilesVendor-Specific Profiles
Physical LayerLink LayerBluetooth Device AddressAdvertising and ScanningConnectionsHost Controller Interface (HCI)Logical Link Control and Adaptation Protocol (L2CAP)Attribute Protocol (ATT)ATT operationsSecurity Manager (SM)Security ProceduresPairing AlgorithmsSecurity KeysGeneric Attribute Profile (GATT)Generic Access Profile (GAP)
RolesModes and ProceduresBroadcast and ObservationDiscoveryDiscoverability modesDiscovery proceduresConnection EstablishmentConnection establishment modesConnection establishment proceduresAdditional GAP ProceduresSecurityAddress TypesAuthenticationSecurity ModesSecurity Modes and ProceduresAdditional GAP DefinitionsAdvertising Data FormatGAP Service
RolesUUIDsAttributesHandleTypePermissionsValueAttribute and Data HierarchyServicesCharacteristicsCharacteristic declaration attributeCharacteristic value attributeCharacteristic DescriptorsExtended Properties DescriptorCharacteristic User Description DescriptorClient Characteristic Configuration DescriptorCharacteristic presentation format descriptorExample ServiceAdvanced Attribute ConceptsAttribute CachingGATT Attribute Data in Advertising PacketsFeaturesExchange MTUService and Characteristic DiscoveryReading Characteristics and DescriptorsWriting Characteristics and DescriptorsServer-Initiated UpdatesSecurityGATT Service
nRF51822-EK (Nordic Semiconductors)Technical SpecificationsSoftDevice ArchitectureWorking with the nRF51822-EKExamples and ToolchainsCC2541DK-MINI (Texas Instruments)Other Hardware Platforms and ModulesLaird’s BL600 ModuleBluegiga’s BLE112/BLE113 ModulesRFDuino
PCA10000 USB Dongle and the Master Control PanelPCA10000 USB Dongle and WiresharkCC2540 USB Dongle and SmartRF SnifferSmartRF-to-Wireshark ConverterBluez hcitool and gatttool
Bluetooth Application AcceleratorSensorTagLightBlue for iOSnRF Master Control Panel for Android
Getting StartedGet the HardwareGet the SoftwareConfigure the HardwareStart a New ProjectInitializing the BLE LibraryConnecting to a Remote DeviceCommunicating with a Remote Device
Simple Battery-Level PeripheralScanning for Remote PeripheralsConnecting to Remote PeripheralsLooking Up Services Associated with a Remote PeripheralLooking Up Characteristics Associated with ServicesMethods for Reading and Decoding CharacteristicsiBeaconAdvertisingRangingImplementing an iBeacon AppApple Notification Center Service with an External Display

mbed BLE APIEmbedded ToolchainsInstalling GNU Tools on OS X and LinuxInstalling GNU Tools on WindowsnRF51822 GNU Codebase and Sample ProjectGetting the nRF51822 GNU CodebasenR51822 GNU Codebase StructureCompiling ProjectsWriting to the nRF51822Going Further

Content preview from Getting Started with Bluetooth Low Energy

Chapter 4. GATT (Services and Characteristics)

The Generic Attribute Profile (GATT) establishes in detail how to exchange all profile and user data over a BLE connection. In contrast with GAP (Chapter 3), which defines the low-level interactions with devices, GATT deals only with actual data transfer procedures and formats.

GATT also provides the reference framework for all GATT-based profiles (discussed in SIG-defined GATT-based profiles), which cover precise use cases and ensure interoperability between devices from different vendors. All standard BLE profiles are therefore based on GATT and must comply with it to operate correctly. This makes GATT a key section of the BLE specification, because every single item of data relevant to applications and users must be formatted, packed, and sent according to its rules.

GATT uses the Attribute Protocol (detailed in Attribute Protocol (ATT)) as its transport protocol to exchange data between devices. This data is organized hierarchically in sections called services, which group conceptually related pieces of user data called characteristics. This determines many fundamental aspects of GATT discussed in this chapter.

Roles

As with any other protocol or profile in the Bluetooth specification, GATT starts by defining the roles that interacting devices can adopt:

Client: The GATT client corresponds to the ATT client discussed in Attribute Protocol (ATT). It sends requests to a server and receives responses (and server-initiated updates) from ...