Ble overview and_implementation
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This document provides an overview of Bluetooth Low Energy (BLE) implementation including the BLE protocol stack, profiles, services and characteristics. It describes the software architecture, states and roles in BLE connections. Details are given on implementing BLE on a CC2541 development kit including defining UUIDs, adding services, handling events and using callbacks. Reference materials for BLE development are also listed.
![BLE Implementation: Profile/Service
1. include profile/service header file in the beginning.
#include “TypicalService.h“
#define MOTIONSENSOR_SERV_UUID 0x5B00
2. Define service UUID format in GLOBAL VARIABLES area
static CONST uint8 motionServiceUUID[ATT_BT_UUID_SIZE] =
{
LO_UINT16(MOTIONSENSOR_SERV_UUID), HI_UINT16(MOTIONSENSOR_SERV_UUID)
};
3. Create Profile Attributes Table
- Motion Service
- Characteristic Declaration
- Characteristic Value "Data"
- Characteristic configuration
- Characteristic User Description](https://image.slidesharecdn.com/bleoverviewandimplementation-140910203445-phpapp02/85/Ble-overview-and_implementation-28-320.jpg)
Ble overview and_implementation
- 1. BLE Overview and Implementation Stanley Chang 02, May. 2014
- 2. Agenda • BLE Protocol Stack • BLE Software Architecture and Structure • GATT Profiles and Services • Implementation
- 3. Protocol Stack • Protocol stack consists of two main sections: • Controller • Host • Solution: single-device, dual-device, network processor. • RF Specifications: • Operates in 2.4 GHz ISM band • 40 channels with 2 MHz spacing • 3 fixed advertisting channels for broadcasting, which avoid 802.11 interferance • 37 adaptively frequency hopped dynamic data channel
- 4. Link Layer • 3 Advertising Channels and 37 Data Channels
- 5. States and Network Topology • Standby-device is not transmitting or receiving any data, and is not connected to any other device • Advertiser -periodically broadcasting advertisements • Scanner -actively looking for advertisers • Initiator -actively trying to initiate a connection with another device • Master -connected to another device as a master • Slave -connected to another device as a slave • BLE is a “star” topology network
- 6. Advertisement Events • A device in the advertising state transmits advertising packets • Advertising packets can contain a data payload • Advertising packets can be directed towards a specific scanner device, or undirected • Advertisements can be connectable or non-connectable (and therefore just used for broadcast of data) • During one “advertising event”, an advertisement packet is transmitted on each of the three advertising channels (37, 38, and 39)
- 7. Connection Parameters • Channel Map: indicates which data channels are used during the connection • Hop Increment: random value between 5 and 16 for channel selection algorithm • Connection Interval: multiple of 1.25ms in range of 7.5ms and 4.0s • Supervision Timeout: multiple of 10ms in the range of 100ms and 32.0s. Must be larger than: (1 + slaveLatency) * (ConnInterval) • Slave Latency: any value between 0 and 499, though it cannot exceed: ((supervisionTimeout / connInterval) –1)
- 9. Logical Link Control and Adaptation Protocol (L2CAP) • Permits upper level protocols and applications to transmit and receive upper layer data packets up to 23 bytes in length. • Provides channel management, allowing for logical channels between two endpoints, supported by the link layer • Connection Parameter Updates
- 10. Security Manager Protocol (SMP) • Performs authentication and key management • AES-128 encryption algorithm • Works with GAP to manage relationships between devices: • Pairing • Authentication • Bonding Bonding
- 11. Generic Access Profile (GAP) • Defines generic procedures for connection-related services: • Device Discovery • Link Establishment • Link Management • Link Termination • Initiation of security features • AES-128 encryption algorithm • Works with GAP to manage relationships between devices: • Pairing • Authentication • Bonding
- 12. GAP Profile Roles • Broadcaster: an advertiser that is non-connectable • Observer: scans for advertisements, but cannot initiate connections. • Peripheral: an advertiser that is connectable and can operate as a slave in a single link layer connection. • Central: scans for advertisements and initiates connections; operates as a master in a single or multiple link layer connections.
- 13. Advertisement and Scan Response Data • “AD” types: • Device Services (e.g. “I am a remote control”) • Service Solicitation (e.g. “I want a remote control to talk to me”) • Device Name • “Flags” -describes the discoverable mode and whether device supports standard Bluetooth or just Low Energy • Tx Power Level • Slave preferred connection interval range • Security support • Manufacturer-specific data
- 14. Attribute Protocol (ATT) • An attribute is a discrete value that has associated with it the following three properties: • A handle (address) • A type • A set of permissions • ATT defines the over-the-air protocol for reading, writing, and discovering attributes • Allows for different permissions to be assigned to attributes, including whether they are readable or writeable, and whether additional security is required for access
- 15. Generic Attribute Profile (GATT) • A profile is composed of one or more “services” necessary to fulfill a use-case • A service may contain certain attributes called “characteristic values”, which are values used by a service • A characteristic value must have a mandatory “characteristic declaration” attribute immediately before the value, containing the properties of the characteristic • Characteristics may also contain optional “descriptor” attributes, with fields such as a configuration or a description
- 16. Service Example
- 17. CC2541DK MINI Kit: SensorTag
- 18. BLE Implementation: UART port
- 19. BLE Implementation: Project option
- 20. BLE Implementation: Application Overview BLE_Bridge 2B00: Control Service 3B00: Voice Note Service 4B00: Notification Service 5B00: Motion Service HAL_UART_DMA HalUARTInit HalUARTOpen HalUARTRead HalUARTWrite Initialization Task event processor Process task message Service change Callback osal_start_system osal_run_system taskEvents table
- 21. Signed GATT Service Profiles UUID
- 22. BLE Implementation: Service UUIDs • Motion UX Service: • 00005B00-0000-1000-8000-00805f9b34fb --> Command Service UUID • 00005B01-0000-1000-8000-00805f9b34fb --> Motion DATA Characteristic (Notification) • 00005B02-0000-1000-8000-00805f9b34fb --> Motion Switcher Characteristic (Writable) • 00005B03-0000-1000-8000-00805f9b34fb --> Motion Pattern Characteristic (Notification) • 00005B04-0000-1000-8000-00805f9b34fb --> Information Request Characteristic (Notification) • 00005B05-0000-1000-8000-00805f9b34fb --> Silence Rington Chacteristic (Writable from ND)
- 23. BLE Implementation: Service UUIDs • Voice Service: • 00003B00-0000-1000-8000-00805f9b34fb --> Voice Service UUID • 00003B01-0000-1000-8000-00805f9b34fb --> Voice AVAILABLE Characteristic (Notification) • 00003B02-0000-1000-8000-00805f9b34fb --> Voice READ Characteristic (Readable from phone) • 00003B03-0000-1000-8000-00805f9b34fb --> Voice ACK Characteristic (Writable from phone)
- 24. BLE Implementation: Service UUIDs • Notification Service: • 00004B00-0000-1000-8000-00805f9b34fb --> Notification Service UUID • 00004B01-0000-1000-8000-00805f9b34fb --> SMS Characteristic (Writable from phone) • 00004B02-0000-1000-8000-00805f9b34fb --> Imcoming Call Characteristic (Writable from phone) • 00004B03-0000-1000-8000-00805f9b34fb --> Missed Call Chacteristic (Writable from phone) • 00004B04-0000-1000-8000-00805f9b34fb --> Time Sync Chacteristic (Writable from phone) • Control Service: • 00002B00-0000-1000-8000-00805f9b34fb --> MicroAppManager Service UUID • 00002B01-0000-1000-8000-00805f9b34fb --> MicroApp Installer Characteristic (Writable from phone) • 00002B02-0000-1000-8000-00805f9b34fb --> MicroApp Installer ACK Characteristic (Notification)
- 25. BLE Implementation: Application Startup Application (BLE_Bridge.c) --> BLE_Bridge_Init() HAL HalUARTInit() User Profile (MotionSensorService.c) - motionData - motionCfg
- 27. BLE Implementation: Value Changes
- 28. BLE Implementation: Profile/Service 1. include profile/service header file in the beginning. #include “TypicalService.h“ #define MOTIONSENSOR_SERV_UUID 0x5B00 2. Define service UUID format in GLOBAL VARIABLES area static CONST uint8 motionServiceUUID[ATT_BT_UUID_SIZE] = { LO_UINT16(MOTIONSENSOR_SERV_UUID), HI_UINT16(MOTIONSENSOR_SERV_UUID) }; 3. Create Profile Attributes Table - Motion Service - Characteristic Declaration - Characteristic Value "Data" - Characteristic configuration - Characteristic User Description
- 29. BLE Implementation: Profile/Service 4. LOCAL FUNCTIONS definition - motion_ReadAttrCB - motion_WriteAttrCB - motion_HandleConnStatusCB 5. PROFILE CALLBACKS definition static CONST gattServiceCBs_t motionCBs = { motion_ReadAttrCB, // Read callback function pointer motion_WriteAttrCB, // Write callback function pointer NULL // Authorization callback function pointer }; 6. PUBLIC FUNCTIONS - MOT_AddService: Initializes motion service by registering GATT attributes with the GATT server. - MOT_SetParameter: Set motion service parameter. - MOT_GetParameter: Get motion service parameter.
- 30. BLE Implementation: Main function • Import related service file in project source, PROFILE. • Add services: • VDR_AddService(GATT_ALL_SERVICES); • NFY_AddService(GATT_ALL_SERVICES); • MOT_AddService(GATT_ALL_SERVICES); • CTL_AddService(GATT_ALL_SERVICES); • Register callbacks with profile: • VOID VDR_RegisterAppCBs(&iv01_vdrCBs); • VOID NFY_RegisterAppCBs(&iv01_nfyCBs); • VOID MOT_RegisterAppCBs(&iv01_motCBs); • VOID CTL_RegisterAppCBs(&iv01_ctlCBs);
- 31. BLE Implementation: Event Process if (events & MOTION_SENSOR_EVT) { if (motionEnabled) { if (MotionDateChanged) { MotionDateChanged = 0; UARTSendCommand(_CMDID_MOTION); ReadMotionData(); } osal_start_timerEx(BLE_Bridge_TaskID, MOTION_SENSOR_EVT, syncPeriod); } return (events ^ MOTION_SENSOR_EVT); }
- 32. BLE Implementation: Callback Value was changed by connected device, then send OSAL event request to handle the related behavior.
- 33. Customized Name The User description will show up as one of the sub-fields when you expand the service and characteristic. The name is taken from an XML file in Program Files (x86)Texas InstrumentsBLE Device Monitorgatt_uuid.xml. The names are aquirred from the SIG profiles which associate a name with an UUID. This metadata is not available over the air, as it's assumed that a UUID is unique and known to both sides for correct operation.
- 34. Reference • BLE_CC2540_DeepDive_Training • TI_BLE_Sample_Applications_Guide • TI_BLE_Software_Developer's_Guide • HAL Driver API • BLE Bridge sample introduction Thank you!