1# 2 3BTstack implements a set of Bluetooth protocols and profiles. To connect to other Bluetooth devices or to provide a Bluetooth services, BTstack has to be properly configured. 4 5The configuration of BTstack is done both at compile time as well as at run time: 6 7- compile time configuration: 8 - adjust *btstack_config.h* - this file describes the system configuration, used functionality, and also the memory configuration 9 - add necessary source code files to your project 10 11- run time configuration of: 12 - Bluetooth chipset 13 - run loop 14 - HCI transport layer 15 - provided services 16 - packet handlers 17 18In the following, we provide an overview of the configuration 19that is necessary to setup BTstack. From the point when the run loop 20is executed, the application runs as a finite 21state machine, which processes events received from BTstack. BTstack 22groups events logically and provides them via packet handlers. 23We provide their overview here. For the case that there is a need to inspect the data exchanged 24between BTstack and the Bluetooth chipset, we describe how to configure 25packet logging mechanism. Finally, we provide an overview on power management in Bluetooth in general and how to save energy in BTstack. 26 27## Configuration in btstack_config.h {#sec:btstackConfigHowTo} 28The file *btstack_config.h* contains three parts: 29 30- \#define HAVE_* directives [listed here](#sec:haveDirectives). These directives describe available system properties, similar to config.h in a autoconf setup. 31- \#define ENABLE_* directives [listed here](#sec:enableDirectives). These directives list enabled properties, most importantly ENABLE_CLASSIC and ENABLE_BLE. 32- other #define directives for BTstack configuration, most notably static memory, [see next section](#sec:memoryConfigurationHowTo) and [NVM configuration](#sec:nvmConfiguration). 33 34<!-- a name "lst:platformConfiguration"></a--> 35<!-- --> 36 37### HAVE_* directives {#sec:haveDirectives} 38System properties: 39 40| \#define | Description | 41|-----------------------|-----------------------------------------------------------------------| 42| HAVE_AES128 | Use platform AES128 engine | 43| HAVE_BTSTACK_STDIN | STDIN is available for CLI interface | 44| HAVE_LWIP | lwIP is available | 45| HAVE_MALLOC | Use dynamic memory | 46| HAVE_MBEDTLS_ECC_P256 | mbedTLS provides NIST P-256 operations e.g. for LE Secure Connections | 47 48Embedded platform properties: 49 50| \#define | Description | 51|---------------------------------|--------------------------------------| 52| HAVE_EMBEDDED_TIME_MS | System provides time in milliseconds | 53| HAVE_EMBEDDED_TICK | System provides tick interrupt | 54| HAVE_HAL_AUDIO | Audio HAL is available | 55| HAVE_HAL_AUDIO_SINK_STEREO_ONLY | Duplicate samples for mono playback | 56 57FreeRTOS platform properties: 58 59| \#define | Description | 60|------------------------------|------------------------------------------------------------------| 61| HAVE_FREERTOS_INCLUDE_PREFIX | FreeRTOS headers are in 'freertos' folder (e.g. ESP32's esp-idf) | 62 63POSIX platform properties: 64 65| \#define | Description | 66|--------------------|--------------------------------------| 67| HAVE_POSIX_FILE_IO | POSIX File i/o used for hci dump | 68| HAVE_POSIX_TIME | System provides time function | 69| LINK_KEY_PATH | Path to stored link keys | 70| LE_DEVICE_DB_PATH | Path to stored LE device information | 71 72<!-- a name "lst:btstackFeatureConfiguration"></a--> 73<!-- --> 74 75Chipset properties: 76 77| \#define | Description | 78|------------------------|-------------------------------------------------------| 79| HAVE_BCM_PCM2 | PCM2 is used and requires additional configuration | 80| HAVE_BCM_PCM_NBS_16KHZ | NBS is up/downsampled, use 16 kHz sample rate for NBS | 81 82### ENABLE_* directives {#sec:enableDirectives} 83BTstack properties: 84 85| \#define | Description | 86|-----------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------| 87| ENABLE_CLASSIC | Enable Classic related code in HCI and L2CAP | 88| ENABLE_BLE | Enable BLE related code in HCI and L2CAP | 89| ENABLE_EHCILL | Enable eHCILL low power mode on TI CC256x/WL18xx chipsets | 90| ENABLE_H5 | Enable support for SLIP mode in `btstack_uart.h` drivers for HCI H5 ('Three-Wire Mode') | 91| ENABLE_LOG_DEBUG | Enable log_debug messages | 92| ENABLE_LOG_ERROR | Enable log_error messages | 93| ENABLE_LOG_INFO | Enable log_info messages | 94| ENABLE_SCO_OVER_HCI | Enable SCO over HCI for chipsets (if supported) | 95| ENABLE_SCO_OVER_PCM | Enable SCO ofer PCM/I2S for chipsets (if supported) | 96| ENABLE_HFP_WIDE_BAND_SPEECH | Enable support for mSBC codec used in HFP profile for Wide-Band Speech | 97| ENABLE_HFP_AT_MESSAGES | Enable `HFP_SUBEVENT_AT_MESSAGE_SENT` and `HFP_SUBEVENT_AT_MESSAGE_RECEIVED` events | 98| ENABLE_LE_PERIPHERAL | Enable support for LE Peripheral Role in HCI and Security Manager | 99| ENABLE_LE_CENTRAL | Enable support for LE Central Role in HCI and Security Manager | 100| ENABLE_LE_SECURE_CONNECTIONS | Enable LE Secure Connections | 101| ENABLE_LE_SECURE_CONNECTIONS_DEBUG_KEY | Enable support for LE Secure Connection debug keys for testing | 102| ENABLE_LE_PROACTIVE_AUTHENTICATION | Enable automatic encryption for bonded devices on re-connect | 103| ENABLE_GATT_CLIENT_PAIRING | Enable GATT Client to start pairing and retry operation on security error | 104| ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS | Use [micro-ecc library](https://github.com/kmackay/micro-ecc) for ECC operations | 105| ENABLE_LE_DATA_LENGTH_EXTENSION | Enable LE Data Length Extension support | 106| ENABLE_LE_ENHANCED_CONNECTION_COMPLETE_EVENT | Enable LE Enhanced Connection Complete Event v1 & v2 | 107| ENABLE_LE_EXTENDED_ADVERTISING | Enable extended advertising and scanning | 108| ENABLE_LE_PERIODIC_ADVERTISING | Enable periodic advertising and scanning | 109| ENABLE_LE_SIGNED_WRITE | Enable LE Signed Writes in ATT/GATT | 110| ENABLE_LE_PRIVACY_ADDRESS_RESOLUTION | Enable address resolution for resolvable private addresses in Controller | 111| ENABLE_CROSS_TRANSPORT_KEY_DERIVATION | Enable Cross-Transport Key Derivation (CTKD) for Secure Connections | 112| ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE | Enable Enhanced Retransmission Mode for L2CAP Channels. Mandatory for AVRCP Browsing | 113| ENABLE_L2CAP_LE_CREDIT_BASED_FLOW_CONTROL_MODE | Enable LE credit-based flow-control mode for L2CAP channels | 114| ENABLE_L2CAP_ENHANCED_CREDIT_BASED_FLOW_CONTROL_MODE | Enable Enhanced credit-based flow-control mode for L2CAP Channels | 115| ENABLE_HCI_CONTROLLER_TO_HOST_FLOW_CONTROL | Enable HCI Controller to Host Flow Control, see below | 116| ENABLE_HCI_SERIALIZED_CONTROLLER_OPERATIONS | Serialize Inquiry, Remote Name Request, and Create Connection operations | 117| ENABLE_ATT_DELAYED_RESPONSE | Enable support for delayed ATT operations, see [GATT Server](profiles/#sec:GATTServerProfile) | 118| ENABLE_BCM_PCM_WBS | Enable support for Wide-Band Speech codec in BCM controller, requires ENABLE_SCO_OVER_PCM | 119| ENABLE_CC256X_ASSISTED_HFP | Enable support for Assisted HFP mode in CC256x Controller, requires ENABLE_SCO_OVER_PCM | 120| Enable_RTK_PCM_WBS | Enable support for Wide-Band Speech codec in Realtek controller, requires ENABLE_SCO_OVER_PCM | 121| ENABLE_CC256X_BAUDRATE_CHANGE_FLOWCONTROL_BUG_WORKAROUND | Enable workaround for bug in CC256x Flow Control during baud rate change, see chipset docs. | 122| ENABLE_CYPRESS_BAUDRATE_CHANGE_FLOWCONTROL_BUG_WORKAROUND | Enable workaround for bug in CYW2070x Flow Control during baud rate change, similar to CC256x. | 123| ENABLE_LE_LIMIT_ACL_FRAGMENT_BY_MAX_OCTETS | Force HCI to fragment ACL-LE packets to fit into over-the-air packet | 124| ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD | Enable use of explicit delete field in TLV Flash implementation - required when flash value cannot be overwritten with zero | 125| ENABLE_TLV_FLASH_WRITE_ONCE | Enable storing of emtpy tag instead of overwriting existing tag - required when flash value cannot be overwritten at all | 126| ENABLE_CONTROLLER_WARM_BOOT | Enable stack startup without power cycle (if supported/possible) | 127| ENABLE_SEGGER_RTT | Use SEGGER RTT for console output and packet log, see [additional options](#sec:rttConfiguration) | 128| ENABLE_EXPLICIT_CONNECTABLE_MODE_CONTROL | Disable calls to control Connectable Mode by L2CAP | 129| ENABLE_EXPLICIT_IO_CAPABILITIES_REPLY | Let application trigger sending IO Capabilities (Negative) Reply | 130| ENABLE_EXPLICIT_LINK_KEY_REPLY | Let application trigger sending Link Key (Negative) Response, allows for asynchronous link key lookup | 131| ENABLE_EXPLICIT_BR_EDR_SECURITY_MANAGER | Report BR/EDR Security Manager support in L2CAP Information Response | 132| ENABLE_EXPLICIT_DEDICATED_BONDING_DISCONNECT | Keep connection after dedicated bonding is complete | 133| ENABLE_CLASSIC_OOB_PAIRING | Enable support for classic Out-of-Band (OOB) pairing | 134| ENABLE_A2DP_EXPLICIT_CONFIG | Let application configure stream endpoint (skip auto-config of SBC endpoint) | 135| ENABLE_AVDTP_ACCEPTOR_EXPLICIT_START_STREAM_CONFIRMATION | allow accept or reject of stream start on A2DP_SUBEVENT_START_STREAM_REQUESTED | 136| ENABLE_LE_WHITELIST_TOUCH_AFTER_RESOLVING_LIST_UPDATE | Enable Workaround for Controller bug | 137| ENABLE_LE_SET_ADV_PARAMS_ON_RANDOM_ADDRESS_CHANGE | Send HCI LE Set Advertising Params after HCI LE Set Random Address - workaround for Controller Bug | 138| ENABLE_CONTROLLER_DUMP_PACKETS | Dump number of packets in Controller per type for debugging | 139| ENABLE_HCI_COMMAND_STATUS_DISCARDED_FOR_FAILED_CONNECTIONS WORKAROUND | Track connection handle for HCI Commands and assume command has failed if disonnect event for connection is received | 140 141Notes: 142 143- ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS: Only some Bluetooth 4.2+ controllers (e.g., EM9304, ESP32) support the necessary HCI commands for ECC. Other reason to enable the ECC software implementations are if the Host is much faster or if the micro-ecc library is already provided (e.g., ESP32, WICED, or if the ECC HCI Commands are unreliable. 144 145### HCI Controller to Host Flow Control 146In general, BTstack relies on flow control of the HCI transport, either via Hardware CTS/RTS flow control for UART or regular USB flow control. If this is not possible, e.g on an SoC, BTstack can use HCI Controller to Host Flow Control by defining ENABLE_HCI_CONTROLLER_TO_HOST_FLOW_CONTROL. If enabled, the HCI Transport implementation must be able to buffer the specified packets. In addition, it also need to be able to buffer a few HCI Events. Using a low number of host buffers might result in less throughput. 147 148Host buffer configuration for HCI Controller to Host Flow Control: 149 150| \#define | Description | 151|-------------------------|----------------------------------| 152| HCI_HOST_ACL_PACKET_NUM | Max number of ACL packets | 153| HCI_HOST_ACL_PACKET_LEN | Max size of HCI Host ACL packets | 154| HCI_HOST_SCO_PACKET_NUM | Max number of ACL packets | 155| HCI_HOST_SCO_PACKET_LEN | Max size of HCI Host SCO packets | 156 157### Memory configuration directives {#sec:memoryConfigurationHowTo} 158 159The structs for services, active connections and remote devices can be 160allocated in two different manners: 161 162- statically from an individual memory pool, whose maximal number of 163 elements is defined in the btstack_config.h file. To initialize the static 164 pools, you need to call at runtime *btstack_memory_init* function. An example 165 of memory configuration for a single SPP service with a minimal 166 L2CAP MTU is shown in Listing {@lst:memoryConfigurationSPP}. 167 168- dynamically using the *malloc/free* functions, if HAVE_MALLOC is 169 defined in btstack_config.h file. 170 171For each HCI connection, a buffer of size HCI_ACL_PAYLOAD_SIZE is reserved. For fast data transfer, however, a large ACL buffer of 1021 bytes is recommended. The large ACL buffer is required for 3-DH5 packets to be used. 172 173<!-- a name "lst:memoryConfiguration"></a--> 174<!-- --> 175 176| \#define | Description | 177|-------------------------------------------|----------------------------------------------------------------------------| 178| HCI_ACL_PAYLOAD_SIZE | Max size of HCI ACL payloads | 179| HCI_ACL_CHUNK_SIZE_ALIGNMENT | Alignment of ACL chunk size, can be used to align HCI transport writes | 180| HCI_INCOMING_PRE_BUFFER_SIZE | Number of bytes reserved before actual data for incoming HCI packets | 181| MAX_NR_BNEP_CHANNELS | Max number of BNEP channels | 182| MAX_NR_BNEP_SERVICES | Max number of BNEP services | 183| MAX_NR_GATT_CLIENTS | Max number of GATT clients | 184| MAX_NR_HCI_CONNECTIONS | Max number of HCI connections | 185| MAX_NR_HFP_CONNECTIONS | Max number of HFP connections | 186| MAX_NR_L2CAP_CHANNELS | Max number of L2CAP connections | 187| MAX_NR_L2CAP_SERVICES | Max number of L2CAP services | 188| MAX_NR_RFCOMM_CHANNELS | Max number of RFOMMM connections | 189| MAX_NR_RFCOMM_MULTIPLEXERS | Max number of RFCOMM multiplexers, with one multiplexer per HCI connection | 190| MAX_NR_RFCOMM_SERVICES | Max number of RFCOMM services | 191| MAX_NR_SERVICE_RECORD_ITEMS | Max number of SDP service records | 192| MAX_NR_SM_LOOKUP_ENTRIES | Max number of items in Security Manager lookup queue | 193| MAX_NR_WHITELIST_ENTRIES | Max number of items in GAP LE Whitelist to connect to | 194 195The memory is set up by calling *btstack_memory_init* function: 196 197 btstack_memory_init(); 198 199<!-- a name "lst:memoryConfigurationSPP"></a--> 200<!-- --> 201 202Here's the memory configuration for a basic SPP server. 203 204 #define HCI_ACL_PAYLOAD_SIZE 52 205 #define MAX_NR_HCI_CONNECTIONS 1 206 #define MAX_NR_L2CAP_SERVICES 2 207 #define MAX_NR_L2CAP_CHANNELS 2 208 #define MAX_NR_RFCOMM_MULTIPLEXERS 1 209 #define MAX_NR_RFCOMM_SERVICES 1 210 #define MAX_NR_RFCOMM_CHANNELS 1 211 #define NVM_NUM_LINK_KEYS 3 212 213Listing: Memory configuration for a basic SPP server. {#lst:memoryConfigurationSPP} 214 215In this example, the size of ACL packets is limited to the minimum of 52 bytes, resulting in an L2CAP MTU of 48 bytes. Only a singleHCI connection can be established at any time. On it, two L2CAP services are provided, which can be active at the same time. Here, these two can be RFCOMM and SDP. Then, memory for one RFCOMM multiplexer is reserved over which one connection can be active. Finally, up to three link keys can be stored in persistent memory. 216 217<!-- --> 218 219### Non-volatile memory (NVM) directives {#sec:nvmConfiguration} 220 221If implemented, bonding information is stored in Non-volatile memory. For Classic, a single link keys and its type is stored. For LE, the bonding information contains various values (long term key, random number, EDIV, signing counter, identity, ...) Often, this is implemented using Flash memory. Then, the number of stored entries are limited by: 222 223<!-- a name "lst:nvmDefines"></a--> 224<!-- --> 225 226| \#define | Description | 227|---------------------------|----------------------------------------------------------------------------------------------| 228| NVM_NUM_LINK_KEYS | Max number of Classic Link Keys that can be stored | 229| NVM_NUM_DEVICE_DB_ENTRIES | Max number of LE Device DB entries that can be stored | 230| NVN_NUM_GATT_SERVER_CCC | Max number of 'Client Characteristic Configuration' values that can be stored by GATT Server | 231 232### HCI Dump Stdout directives {#sec:hciDumpStdout} 233 234Allow to truncate HCI ACL and SCO packets to reduce console output for debugging audio applications. 235 236| \#define | Description | 237|------------------------------|-------------------------------------------| 238| HCI_DUMP_STDOUT_MAX_SIZE_ACL | Max size of ACL packets to log via stdout | 239| HCI_DUMP_STDOUT_MAX_SIZE_SCO | Max size of SCO packets to log via stdout | 240| HCI_DUMP_STDOUT_MAX_SIZE_ISO | Max size of ISO packets to log via stdout | 241 242### SEGGER Real Time Transfer (RTT) directives {#sec:rttConfiguration} 243 244[SEGGER RTT](https://www.segger.com/products/debug-probes/j-link/technology/about-real-time-transfer/) improves on the use of an UART for debugging with higher throughput and less overhead. In addition, it allows for direct logging in PacketLogger/BlueZ format via the provided JLinkRTTLogger tool. 245 246When enabled with `ENABLE_SEGGER_RTT` and `hci_dump_init()` can be called with an `hci_dunp_segger_stdout_get_instance()` for textual output and `hci_dump_segger_binary_get_instance()` for binary output. With the latter, you can select `HCI_DUMP_BLUEZ` or `HCI_DUMP_PACKETLOGGER`, format. For RTT, the following directives are used to configure the up channel: 247 248| \#define | Default | Description | 249|----------------------------------|-------------------------------|-------------------------------------------------------------------------------------------------------------------| 250| SEGGER_RTT_PACKETLOG_MODE | SEGGER_RTT_MODE_NO_BLOCK_SKIP | SEGGER_RTT_MODE_NO_BLOCK_SKIP to skip messages if buffer is full, or, SEGGER_RTT_MODE_BLOCK_IF_FIFO_FULL to block | 251| SEGGER_RTT_PACKETLOG_CHANNEL | 1 | Channel to use for packet log. Channel 0 is used for terminal | 252| SEGGER_RTT_PACKETLOG_BUFFER_SIZE | 1024 | Size of outgoing ring buffer. Increase if you cannot block but get 'message skipped' warnings. | 253 254## Run-time configuration 255 256To allow code-reuse with different platforms 257as well as with new ports, the low-level initialization of BTstack and 258the hardware configuration has been extracted to the various 259*platforms/PLATFORM/main.c* files. The examples only contain the 260platform-independent Bluetooth logic. But let’s have a look at the 261common init code. 262 263Listing [below](#lst:btstackInit) shows a minimal platform setup for an 264embedded system with a Bluetooth chipset connected via UART. 265 266~~~~ {#lst:btstackInit .c caption="{Minimal platform setup for an embedded system}"} 267 268 int main(){ 269 // ... hardware init: watchdoch, IOs, timers, etc... 270 271 // setup BTstack memory pools 272 btstack_memory_init(); 273 274 // select embedded run loop 275 btstack_run_loop_init(btstack_run_loop_embedded_get_instance()); 276 277 // enable logging 278 hci_dump_init(hci_dump_embedded_stdout_get_instance()); 279 280 281 // init HCI 282 hci_transport_t * transport = hci_transport_h4_instance(); 283 hci_init(transport, NULL); 284 285 // setup example 286 btstack_main(argc, argv); 287 288 // go 289 btstack_run_loop_execute(); 290 } 291 292~~~~ 293 294First, BTstack’s memory pools are set up. Then, the standard run loop 295implementation for embedded systems is selected. 296 297The call to *hci_dump_init* configures BTstack to output all Bluetooth 298packets and its own debug and error message using printf with BTstack's 299millisecond tiomestamps.s as tim. 300The Python 301script *tools/create_packet_log.py* can be used to convert the console 302output into a Bluetooth PacketLogger format that can be opened by the OS 303X PacketLogger tool as well as by Wireshark for further inspection. When 304asking for help, please always include a log created with HCI dump. 305 306The *hci_init* function sets up HCI to use the HCI H4 Transport 307implementation. It doesn’t provide a special transport configuration nor 308a special implementation for a particular Bluetooth chipset. It makes 309use of the *remote_device_db_memory* implementation that allows for 310re-connects without a new pairing but doesn’t persist the bonding 311information. 312 313Finally, it calls *btstack_main()* of the actual example before 314executing the run loop. 315 316 317## Source tree structure {#sec:sourceTreeHowTo} 318 319The source tree has been organized to easily setup new projects. 320 321| Path | Description | 322|----------|------------------------------------------------------| 323| chipset | Support for individual Bluetooth Controller chipsets | 324| doc | Sources for BTstack documentation | 325| example | Example applications available for all ports | 326| platform | Support for special OSs and/or MCU architectures | 327| port | Complete port for a MCU + Chipset combinations | 328| src | Bluetooth stack implementation | 329| test | Unit and PTS tests | 330| tool | Helper tools for BTstack | 331 332The core of BTstack, including all protocol and profiles, is in *src/*. 333 334Support for a particular platform is provided by the *platform/* subfolder. For most embedded ports, *platform/embedded/* provides *btstack_run_loop_embedded* and the *hci_transport_h4_embedded* implementation that require *hal_cpu.h*, *hal_led.h*, and *hal_uart_dma.h* plus *hal_tick.h* or *hal_time_ms* to be implemented by the user. 335 336To accommodate a particular Bluetooth chipset, the *chipset/* subfolders provide various btstack_chipset_* implementations. 337Please have a look at the existing ports in *port/*. 338 339## Run loop configuration {#sec:runLoopHowTo} 340 341To initialize BTstack you need to [initialize the memory](#sec:memoryConfigurationHowTo) 342and [the run loop](#sec:runLoopHowTo) respectively, then setup HCI and all needed higher 343level protocols. 344 345BTstack uses the concept of a run loop to handle incoming data and to schedule work. 346The run loop handles events from two different types of sources: data 347sources and timers. Data sources represent communication interfaces like 348an UART or an USB driver. Timers are used by BTstack to implement 349various Bluetooth-related timeouts. They can also be used to handle 350periodic events. In addition, most implementations also allow to trigger a poll 351of the data sources from interrupt context, or, execute a function from a different 352thread. 353 354Data sources and timers are represented by the *btstack_data_source_t* and 355*btstack_timer_source_t* structs respectively. Each of these structs contain 356at least a linked list node and a pointer to a callback function. All active timers 357and data sources are kept in link lists. While the list of data sources 358is unsorted, the timers are sorted by expiration timeout for efficient 359processing. Data sources need to be configured upon what event they are called back. 360They can be configured to be polled (*DATA_SOURCE_CALLBACK_POLL*), on read ready (*DATA_SOURCE_CALLBACK_READ*), 361or on write ready (*DATA_SOURCE_CALLBACK_WRITE*). 362 363Timers are single shot: a timer will be removed from the timer list 364before its event handler callback is executed. If you need a periodic 365timer, you can re-register the same timer source in the callback 366function, as shown in Listing [PeriodicTimerHandler]. Note that BTstack 367expects to get called periodically to keep its time, see Section 368[on time abstraction](#sec:timeAbstractionPorting) for more on the 369tick hardware abstraction. 370 371BTstack provides different run loop implementations that implement the *btstack_run_loop_t* interface: 372 373- CoreFoundation: implementation for iOS and OS X applications 374- Embedded: the main implementation for embedded systems, especially without an RTOS. 375- FreeRTOS: implementation to run BTstack on a dedicated FreeRTOS thread 376- POSIX: implementation for POSIX systems based on the select() call. 377- Qt: implementation for the Qt applications 378- WICED: implementation for the Broadcom WICED SDK RTOS abstraction that wraps FreeRTOS or ThreadX. 379- Windows: implementation for Windows based on Event objects and WaitForMultipleObjects() call. 380 381Depending on the platform, data sources are either polled (embedded, FreeRTOS), or the platform provides a way 382to wait for a data source to become ready for read or write (CoreFoundation, POSIX, Qt, Windows), or, 383are not used as the HCI transport driver and the run loop is implemented in a different way (WICED). 384In any case, the callbacks must be explicitly enabled with the *btstack_run_loop_enable_data_source_callbacks(..)* function. 385 386In your code, you'll have to configure the run loop before you start it 387as shown in Listing [listing:btstackInit]. The application can register 388data sources as well as timers, e.g., for periodical sampling of sensors, or 389for communication over the UART. 390 391The run loop is set up by calling *btstack_run_loop_init* function and providing 392an instance of the actual run loop. E.g. for the embedded platform, it is: 393 394<!-- --> 395 396 btstack_run_loop_init(btstack_run_loop_embedded_get_instance()); 397 398If the run loop allows to trigger polling of data sources from interrupt context, 399*btstack_run_loop_poll_data_sources_from_irq*. 400 401On multi-threaded environments, e.g., FreeRTOS, POSIX, WINDOWS, 402*btstack_run_loop_execute_code_on_main_thread* can be used to schedule a callback on the main loop. 403 404The complete Run loop API is provided [here](appendix/apis/#sec:runLoopAPIAppendix). 405 406 407### Run Loop Embedded 408 409In the embedded run loop implementation, data sources are constantly polled and 410the system is put to sleep if no IRQ happens during the poll of all data sources. 411 412The complete run loop cycle looks like this: first, the callback 413function of all registered data sources are called in a round robin way. 414Then, the callback functions of timers that are ready are executed. 415Finally, it will be checked if another run loop iteration has been 416requested by an interrupt handler. If not, the run loop will put the MCU 417into sleep mode. 418 419Incoming data over the UART, USB, or timer ticks will generate an 420interrupt and wake up the microcontroller. In order to avoid the 421situation where a data source becomes ready just before the run loop 422enters sleep mode, an interrupt-driven data source has to call the 423*btstack_run_loop_poll_data_sources_from_irq* function. The call to 424*btstack_run_loop_poll_data_sources_from_irq* sets an 425internal flag that is checked in the critical section just before 426entering sleep mode causing another run loop cycle. 427 428To enable the use of timers, make sure that you defined HAVE_EMBEDDED_TICK or HAVE_EMBEDDED_TIME_MS in the 429config file. 430 431While there is no threading, *btstack_run_loop_poll_data_sources_from_irq* allows to reduce stack size by 432scheduling a continuation. 433 434### Run Loop FreeRTOS 435 436The FreeRTOS run loop is used on a dedicated FreeRTOS thread and it uses a FreeRTOS queue to schedule callbacks on the run loop. 437In each iteration: 438 439- all data sources are polled 440- all scheduled callbacks are executed 441- all expired timers are called 442- finally, it gets the next timeout. It then waits for a 'trigger' or the next timeout, if set. 443 444It supports both *btstack_run_loop_poll_data_sources_from_irq* as well as *btstack_run_loop_execute_code_on_main_thread*. 445 446 447### Run Loop POSIX 448 449The data sources are standard File Descriptors. In the run loop execute implementation, 450select() call is used to wait for file descriptors to become ready to read or write, 451while waiting for the next timeout. 452 453To enable the use of timers, make sure that you defined HAVE_POSIX_TIME in the config file. 454 455It supports both *btstack_run_loop_poll_data_sources_from_irq* as well as *btstack_run_loop_execute_code_on_main_thread*. 456 457 458### Run loop CoreFoundation (OS X/iOS) 459 460This run loop directly maps BTstack's data source and timer source with CoreFoundation objects. 461It supports ready to read and write similar to the POSIX implementation. The call to 462*btstack_run_loop_execute()* then just calls *CFRunLoopRun()*. 463 464To enable the use of timers, make sure that you defined HAVE_POSIX_TIME in the config file. 465 466It currently only supports *btstack_run_loop_execute_code_on_main_thread*. 467 468 469### Run Lop Qt 470 471This run loop directly maps BTstack's data source and timer source with Qt Core objects. 472It supports ready to read and write similar to the POSIX implementation. 473 474To enable the use of timers, make sure that you defined HAVE_POSIX_TIME in the config file. 475 476It supports both *btstack_run_loop_poll_data_sources_from_irq* as well as *btstack_run_loop_execute_code_on_main_thread*. 477 478 479### Run loop Windows 480 481The data sources are Event objects. In the run loop implementation WaitForMultipleObjects() call 482is all is used to wait for the Event object to become ready while waiting for the next timeout. 483 484It supports both *btstack_run_loop_poll_data_sources_from_irq* as well as *btstack_run_loop_execute_code_on_main_thread*. 485 486 487### Run loop WICED 488 489WICED SDK API does not provide asynchronous read and write to the UART and no direct way to wait for 490one or more peripherals to become ready. Therefore, BTstack does not provide direct support for data sources. 491Instead, the run loop provides a message queue that allows to schedule functions calls on its thread via 492*btstack_run_loop_wiced_execute_code_on_main_thread()*. 493 494The HCI transport H4 implementation then uses two lightweight threads to do the 495blocking read and write operations. When a read or write is complete on 496the helper threads, a callback to BTstack is scheduled. 497 498It currently only supports *btstack_run_loop_execute_code_on_main_thread*. 499 500 501## HCI Transport configuration 502 503The HCI initialization has to adapt BTstack to the used platform. The first 504call is to *hci_init()* and requires information about the HCI Transport to use. 505The arguments are: 506 507- *HCI Transport implementation*: On embedded systems, a Bluetooth 508 module can be connected via USB or an UART port. On embedded, BTstack implements HCI UART Transport Layer (H4) and H4 with eHCILL support, a lightweight low-power variant by Texas Instruments. For POSIX, there is an implementation for HCI H4, HCI H5 and H2 libUSB, and for WICED HCI H4 WICED. 509 These are accessed by linking the appropriate file, e.g., 510 [platform/embedded/hci_transport_h4_embedded.c]() 511 and then getting a pointer to HCI Transport implementation. 512 For more information on adapting HCI Transport to different 513 environments, see [here](porting/#sec:hciTransportPorting). 514 515<!-- --> 516 517 hci_transport_t * transport = hci_transport_h4_instance(); 518 519- *HCI Transport configuration*: As the configuration of the UART used 520 in the H4 transport interface are not standardized, it has to be 521 provided by the main application to BTstack. In addition to the 522 initial UART baud rate, the main baud rate can be specified. The HCI 523 layer of BTstack will change the init baud rate to the main one 524 after the basic setup of the Bluetooth module. A baud rate change 525 has to be done in a coordinated way at both HCI and hardware level. 526 For example, on the CC256x, the HCI command to change the baud rate 527 is sent first, then it is necessary to wait for the confirmation event 528 from the Bluetooth module. Only now, can the UART baud rate changed. 529 530<!-- --> 531 532 hci_uart_config_t* config = &hci_uart_config; 533 534After these are ready, HCI is initialized like this: 535 536 hci_init(transport, config); 537 538 539In addition to these, most UART-based Bluetooth chipset require some 540special logic for correct initialization that is not covered by the 541Bluetooth specification. In particular, this covers: 542 543- setting the baudrate 544- setting the BD ADDR for devices without an internal persistent storage 545- upload of some firmware patches. 546 547This is provided by the various *btstack_chipset_t* implementation in the *chipset/* subfolders. 548As an example, the *bstack_chipset_cc256x_instance* function returns a pointer to a chipset struct 549suitable for the CC256x chipset. 550 551<!-- --> 552 553 btstack_chipset_t * chipset = btstack_chipset_cc256x_instance(); 554 hci_set_chipset(chipset); 555 556 557In some setups, the hardware setup provides explicit control of Bluetooth power and sleep modes. 558In this case, a *btstack_control_t* struct can be set with *hci_set_control*. 559 560Finally, the HCI implementation requires some form of persistent storage for link keys generated 561during either legacy pairing or the Secure Simple Pairing (SSP). This commonly requires platform 562specific code to access the MCU’s EEPROM of Flash storage. For the 563first steps, BTstack provides a (non) persistent store in memory. 564For more see [here](porting/#sec:persistentStoragePorting). 565 566<!-- --> 567 568 btstack_link_key_db_t * link_key_db = &btstack_link_key_db_memory_instance(); 569 btstack_set_link_key_db(link_key_db); 570 571 572The higher layers only rely on BTstack and are initialized by calling 573the respective *\*_init* function. These init functions register 574themselves with the underlying layer. In addition, the application can 575register packet handlers to get events and data as explained in the 576following section. 577 578 579## Services {#sec:servicesHowTo} 580 581One important construct of BTstack is *service*. A service represents a 582server side component that handles incoming connections. So far, BTstack 583provides L2CAP, BNEP, and RFCOMM services. An L2CAP service handles incoming 584connections for an L2CAP channel and is registered with its protocol 585service multiplexer ID (PSM). Similarly, an RFCOMM service handles 586incoming RFCOMM connections and is registered with the RFCOMM channel 587ID. Outgoing connections require no special registration, they are 588created by the application when needed. 589 590 591## Packet handlers configuration {#sec:packetHandlersHowTo} 592 593 594After the hardware and BTstack are set up, the run loop is entered. From 595now on everything is event driven. The application calls BTstack 596functions, which in turn may send commands to the Bluetooth module. The 597resulting events are delivered back to the application. Instead of 598writing a single callback handler for each possible event (as it is done 599in some other Bluetooth stacks), BTstack groups events logically and 600provides them over a single generic interface. Appendix 601[Events and Errors](generated/appendix/#sec:eventsAndErrorsAppendix) 602summarizes the parameters and event 603codes of L2CAP and RFCOMM events, as well as possible errors and the 604corresponding error codes. 605 606Here is summarized list of packet handlers that an application might 607use: 608 609- HCI event handler - allows to observer HCI, GAP, and general BTstack events. 610 611- L2CAP packet handler - handles LE Connection parameter requeset updates 612 613- L2CAP service packet handler - handles incoming L2CAP connections, 614 i.e., channels initiated by the remote. 615 616- L2CAP channel packet handler - handles outgoing L2CAP connections, 617 i.e., channels initiated internally. 618 619- RFCOMM service packet handler - handles incoming RFCOMM connections, 620 i.e., channels initiated by the remote. 621 622- RFCOMM channel packet handler - handles outgoing RFCOMM connections, 623 i.e., channels initiated internally. 624 625These handlers are registered with the functions listed in Table 626{@tbl:registeringFunction}. 627 628 629| Packet Handler | Registering Function | 630|-------------------------------|--------------------------------------------------------------------------| 631| HCI packet handler | hci_add_event_handler | 632| L2CAP packet handler | l2cap_register_packet_handler | 633| L2CAP service packet handler | l2cap_register_service | 634| L2CAP channel packet handler | l2cap_create_channel | 635| RFCOMM service packet handler | rfcomm_register_service and rfcomm_register_service_with_initial_credits | 636| RFCOMM channel packet handler | rfcomm_create_channel and rfcomm_create_channel_with_initial_credits | 637 638Table: Functions for registering packet handlers. {#tbl:registeringFunction} 639 640HCI, GAP, and general BTstack events are delivered to the packet handler 641specified by *hci_add_event_handler* function. In L2CAP, 642BTstack discriminates incoming and outgoing connections, i.e., event and 643data packets are delivered to different packet handlers. Outgoing 644connections are used access remote services, incoming connections are 645used to provide services. For incoming connections, the packet handler 646specified by *l2cap_register_service* is used. For outgoing 647connections, the handler provided by *l2cap_create_channel* 648is used. RFCOMM and BNEP are similar. 649 650The application can register a single shared packet handler for all 651protocols and services, or use separate packet handlers for each 652protocol layer and service. A shared packet handler is often used for 653stack initialization and connection management. 654 655Separate packet handlers can be used for each L2CAP service and outgoing 656connection. For example, to connect with a Bluetooth HID keyboard, your 657application could use three packet handlers: one to handle HCI events 658during discovery of a keyboard registered by 659*l2cap_register_packet_handler*; one that will be registered to an 660outgoing L2CAP channel to connect to keyboard and to receive keyboard 661data registered by *l2cap_create_channel*; after that 662keyboard can reconnect by itself. For this, you need to register L2CAP 663services for the HID Control and HID Interrupt PSMs using 664*l2cap_register_service*. In this call, you’ll also specify 665a packet handler to accept and receive keyboard data. 666 667All events names have the form MODULE_EVENT_NAME now, e.g., *gap_event_-advertising_report*. 668To facilitate working with 669events and get rid of manually calculating offsets into packets, BTstack provides 670auto-generated getters for all fields of all events in *src/hci_event.h*. All 671functions are defined as static inline, so they are not wasting any program memory 672if not used. If used, the memory footprint should be identical to accessing the 673field directly via offsets into the packet. For example, to access fields address_type 674and address from the *gap_event_advertising_report* event use following getters: 675 676<!-- --> 677 uint8_t address type = gap_event_advertising_report_get_address_type(event); 678 bd_addr_t address; 679 gap_event_advertising_report_get_address(event, address); 680 681 682## Bluetooth HCI Packet Logs {#sec:packetlogsHowTo} 683 684If things don't work as expected, having a look at the data exchanged 685between BTstack and the Bluetooth chipset often helps. 686 687For this, BTstack provides a configurable packet logging mechanism via hci_dump.h and the following implementations: 688 689 void hci_dump_init(const hci_dump_t * hci_dump_implementation); 690 691| Platform | File | Description | 692|----------|------------------------------|----------------------------------------------------| 693| POSIX | `hci_dump_posix_fs.c` | HCI log file for Apple PacketLogger and Wireshark | 694| POSIX | `hci_dump_posix_stdout.c` | Console output via printf | 695| Embedded | `hci_dump_embedded_stdout.c` | Console output via printf | 696| Embedded | `hci_dump_segger_stdout.c` | Console output via SEGGER RTT | 697| Embedded | `hci_dump_segger_binary.c` | HCI log file for Apple PacketLogger via SEGGER RTT | 698 699On POSIX systems, you can call *hci_dump_init* with a *hci_dump_posix_fs_get_instance()* and 700configure the path and output format with *hci_dump_posix_fs_open(const char * path, hci_dump_format_t format)* 701where format can be *HCI_DUMP_BLUEZ* or *HCI_DUMP_PACKETLOGGER*. 702The resulting file can be analyzed with Wireshark or the Apple's PacketLogger tool. 703 704On embedded systems without a file system, you either log to an UART console via printf or use SEGGER RTT. 705For printf output you pass *hci_dump_embedded_stdout_get_instance()* to *hci_dump_init()*. 706With RTT, you can choose between textual output similar to printf, and binary output. 707For textual output, you can provide the *hci_dump_segger_stdout_get_instance()*. 708 709It will log all HCI packets to the UART console via printf or RTT Terminal. 710If you capture the console output, incl. your own debug messages, you can use 711the create_packet_log.py tool in the tools folder to convert a text output into a 712PacketLogger file. 713 714For less overhead and higher logging speed, you can directly log in binary format by 715passing *hci_dump_segger_rtt_binary_get_instance()* and selecting the output format by 716calling *hci_dump_segger_rtt_binary_open(hci_dump_format_t format)* with the same format as above. 717 718 719In addition to the HCI packets, you can also enable BTstack's debug information by adding 720 721 #define ENABLE_LOG_INFO 722 #define ENABLE_LOG_ERROR 723 724to the btstack_config.h and recompiling your application. 725 726## Bluetooth Power Control {#sec:powerControl} 727 728In most BTstack examples, the device is set to be discoverable and connectable. In this mode, even when there's no active connection, the Bluetooth Controller will periodically activate its receiver in order to listen for inquiries or connecting requests from another device. 729The ability to be discoverable requires more energy than the ability to be connected. Being discoverable also announces the device to anybody in the area. Therefore, it is a good idea to pause listening for inquiries when not needed. Other devices that have your Bluetooth address can still connect to your device. 730 731To enable/disable discoverability, you can call: 732 733 /** 734 * @brief Allows to control if device is discoverable. OFF by default. 735 */ 736 void gap_discoverable_control(uint8_t enable); 737 738If you don't need to become connected from other devices for a longer period of time, you can also disable the listening to connection requests. 739 740To enable/disable connectability, you can call: 741 742 /** 743 * @brief Override page scan mode. Page scan mode enabled by l2cap when services are registered 744 * @note Might be used to reduce power consumption while Bluetooth module stays powered but no (new) 745 * connections are expected 746 */ 747 void gap_connectable_control(uint8_t enable); 748 749For Bluetooth Low Energy, the radio is periodically used to broadcast advertisements that are used for both discovery and connection establishment. 750 751To enable/disable advertisements, you can call: 752 753 /** 754 * @brief Enable/Disable Advertisements. OFF by default. 755 * @param enabled 756 */ 757 void gap_advertisements_enable(int enabled); 758 759If a Bluetooth Controller is neither discoverable nor connectable, it does not need to periodically turn on its radio and it only needs to respond to commands from the Host. In this case, the Bluetooth Controller is free to enter some kind of deep sleep where the power consumption is minimal. 760 761Finally, if that's not sufficient for your application, you could request BTstack to shutdown the Bluetooth Controller. For this, the "on" and "off" functions in the btstack_control_t struct must be implemented. To shutdown the Bluetooth Controller, you can call: 762 763 /** 764 * @brief Requests the change of BTstack power mode. 765 */ 766 int hci_power_control(HCI_POWER_MODE mode); 767 768with mode set to *HCI_POWER_OFF*. When needed later, Bluetooth can be started again via by calling it with mode *HCI_POWER_ON*, as seen in all examples. 769