xref: /btstack/CHANGELOG.md (revision e938c062fda498bb7e1f80caf014a4004700fa6c)

# Change Log
All notable changes to this project will be documented in this file.

The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).

---

## Unreleased

### Added
- HFP HF: send custom AT command with hfp_hf_send_at_command
- HFP HF: terminate held calls with hfp_hf_terminate_held_calls
- HFP HF: provide Call Waiting information alpha field
- HFP AG: support handling of custom AT commands with hfp_ag_register_custom_at_command
- HFP AG: send custom unsolicited result code with hfp_ag_send_unsolicited_result_code
- GAP: support BIG with gap_big_create and gap_big_terminate
- GAP: support BIG Sync gap_big_sync_create and gap_big_sync_terminate
- port: CMake build files in all windows-* ports allow to use Visual Studio 2022
- embedded audio: mono audio is played on both channels if HAVE_HAL_AUDIO_SINK_STEREO_ONLY is defined

### Fixed
- HCI: only add paired LE devices with IRK to resolving list
- GAP: use static random address after power up

### Changed
- HCI Dump: provide log level to log_message implementation
- GAP: replace BTSTACK_EVENT_DISCOVERABLE_ENABLED with BTSTACK_EVENT_SCAN_MODE_CHANGED


## Release v1.5.3

### Added
- GAP: support periodic advertising with ENABLE_LE_PERIODIC_ADVERTISING
- GAP: support periodic inquiry mode with gap_inquiry_periodic_start
- HFP HF: provide Calling Line Identification alpha field
- HFP HF: emit HFP_SUBEVENT_TRANSMIT_DTMF_CODES after sending DTMF command
- GOEP Server
- Chipset: support for firmware download and configuration of Realtek Controllers

### Fixed
- GAP: fix gap_connect_cancel for gap_connect_with_whitelist
- GAP: fix race condition that causes duplicate authenticate request
- SM: address update for non-resolvable private addresses
- SM: reset state on power off transition
- L2CAP: Fix accept incoming ERTM connection when Information Request already complete
- A2DP Sink: fix config API for AAC, ATRAC, and other codecs
- HFP: try next link setting for SCO connection failure after SCO reject errors
- HFP AG: activate all AG indicators upon service level connection establishment
- HFP AG: handle call termination in alerting call state
- HFP HF: fix parsing of phone number for voice tag
- HFP HF: report HFP_SUBEVENT_NETWORK_OPERATOR_CHANGED event

### Changed
- HCI: use ERROR_CODE_CONNECTION_REJECTED_DUE_TO_SECURITY_REASONS to rejected classic connections
- SM: pairing events indicate if LE Secure Connection will be used
- A2DP: new a2dp.c contains shared code of Sink and Source roles
- A2DP Sink: automatically configure stream endpoint for outgoing connections
- HFP AG: drop unused number parameter from hfp_ag_outgoing_call_initiated
- libusb: command line options to delete TLV and specify log file path
- Windows: native implementations of btstack_tlv_window, hci_dump_windows_fs, hci_dump_window_stdout

## Release v1.5.2

### Added
- GAP: ENABLE_HCI_SERIALIZED_CONTROLLER_OPERATIONS serializes Inquiry, Remote Name Request and Create Connection operations
- GAP: support extended advertising with ENABLE_LE_EXTENDED_ADVERTISING
- GAP: gap_enable_link_watchdog() uses automatic flush timeout to disconnect if data cannot be sent
- GAP: gap_secure_connections_active() to query if BR/EDR Secure Connecions are possible
- ATT DB: provide gatt_server_get_handle_range_for_service_with_uuid16 to find included service within handle range
- GATT Service: Audio Input Control Service Server (AICS 1.0)
- GATT Service: Microphone Control Service Server (MCS 1.0)
- GATT Service: Volume Control Service Server (VCS 1.0)
- GATT Service: Volume Offset Control Service Server (VOCS 1.0)

### Fixed
- POSIX: fix RTS/CTS configuration by keeping local termios copy in btstack_uart_posix
- HCI: fix handling of HCI Connection Complete with error (regression introduced in v1.5.1)
- GAP: disable scanning, advertising, connection before updating random address
- GAP: fix LE Scan with whitelist
- HFP_AG: fix tracking for call dropped during outgoing ringing
- HFP: Free HFP Connection object on SDP error / Service not found
- PBAP Client: emit operation complete with status OBEX_ABORTED

### Changed
- Chipset: use da145xx in folder/file/function names for Dialog Semiconductor SoCs
- GAP: set min encryption key size during init, if supported
- AVDTP: use BLUETOOTH_SERVICE_CLASS_AUDIO_SINK / SOURCE instead of BLUETOOTH_PROTOCOL_AVDTP in SDP queries
- ATT Server: use uint8_t for status returns
- libusb, POSIX and Windows ports: use '-' instead of ':' in btstack_BD_ADDR.tlv filename


## Release v1.5.1

### Added
- GOEP Client: add goep_client_version_20_or_higher
- ESP32: implement audio source

### Fixed
- PBAP Client: support disconnect while operation is ongoing
- PBAP Client: use SRM only if GOEP v2.0 or higher connection
- PBAP Client: emit vCard entry data as PBAP_DATA_PACKET
- L2CAP: limit remote MTU by local tx configuration in ERTM

### Changed
- Example: init SM if LE supported to avoid issue with Android Cross-Transport Key-Derivation
- ESP32: update sdkconfig for esp-idf v4.3, disable Bluedroid host stack
- ESP32: use I2S configuration from ESP32 LyraT V4.3


## Release v1.5.0

### Added
- HCI Dump: Support BTSnoop format in hci_dump_posix_fs.c for format = HCI_DUMP_BTSNOOP
- HCI Dump RTT STDOUT: drop messages if RTT buffer is full and RTT is configured for non-blocking
- HCI: hci_remove_event_handler to remove packet handler
- hci_cmd: support variable length fields and arrayed parameters
- GAP: ENABLE_EXPLICIT_LINK_KEY_REPLY allows for asynchronous link key lookup by application
- GAP: gap_set_page_timeout to set Page Timeout
- GAP: gap_inquiry_set_scan_activity to set Inquiry Scan Activity
- L2CAP: emit L2CAP_EVENT_INFORMATION_RESPONSE event with extended features and fixed channels supported
- L2CAP: support Enhanced Credit-based Flow-Control Mode for connection-oriented channels over BR/EDR/LE
- A2DP: allow to register media codec validator for sink and source with:
  - `a2dp_sink_register_media_config_validator`
  - `a2dp_source_register_media_config_validator`
- A2DP Sink: allow accept or reject of stream start on A2DP_SUBEVENT_START_STREAM_REQUESTED when ENABLE_AVDTP_ACCEPTOR_EXPLICIT_START_STREAM_CONFIRMATION is defined
- OBEX: new obex_parser for chunked OBEX data
- SM: Support Cross-Transport Key-Derivation (CTKD) of LE LTK from BR/EDR SC Link Key in Responder role
- SM: sm_remove_event_handler to remove packet handler
- GATT Service: Bond Management Service (BMS 1.0) Server
- GATT Service: Microphone Control Service (MICS 1.0) Server
- GATT Service: TX Power Service (TPS 1.0) Server
- POSIX: btstack_signal allows to register for callback on signal, e.g. ctrl-c
- Windows: btstack_stdin_window_register_ctrl_c_callback allows to register for ctrl-c

### Fixed
- A2DP Source: fix reconfigure
- AVRCP Controller: prevent registering of notifications for unsupported events
- RFCOMM: fixed handling of remote port configuration command
- HFP AG: fix accept incoming connection while audio connection is established
- PBAP Client: handle chunked vCard Listing
- PBAP Client: use new streaming obex_parser to handle chunked OBEX data
- SM: Work around for unexpected Windows 10 disconnect for BR Secure Connections (SMP over BR timeout)
- SM: support storing bonding information for devices with identical IRK but different public addresses
- GAP: restart advertising when private address changes
- le_device_db_tlv: keep number of devices reported by le_device_db_count if old entry is replaced

### Changed
- Drop iOS support
- HCI: provide status instead of undocumented int error code and bool for API functions
- HCI: use 1000 ms watchdog to force power off for hci_power_control(HCI_POWER_OFF)
- GAP: local name, EIR data, class of device and default link policy can be updated at any time
- L2CAP: provide status instead of undocumented int error code and bool for API functions
- L2CAP: remote features not required for SDP connections
- L2CAP: replaced l2cap_register_packet_handler with l2cap_add_event_handler to register multiple handlers
- L2CAP: drop reason parameter in l2cap_disconnect
- L2CAP: use official terminology for L2CAP channel modes - ENABLE_L2CAP_LE_CREDIT_BASED_FLOW_CONTROL_MODE replaces ENABLE_LE_DATA_CHANNELS
- L2CAP: unify API for can send now, request to send, and send packet and disconnect channel
- L2CAP: unify events for can send now, packet sent, channel closed (CbM/ECBM using existing events)
- RFCOMM: `RFCOMM_EVENT_PORT_CONFIGURATION` contains rfcomm_cid and remote flag, emitted for query config
- RFCOMM: provide status instead of undocumented int error code and bool for API functions
- RFCOMM: remote port configuration, line status, and modem status are sent by channel state machine
- HSP: add ACL Connection to all events and BD ADDR to HSP_SUBEVENT_RFCOMM_CONNECTION_COMPLETE
- HFP: API functions return status code if appropriate
- HFP: removed one parameter from hfp_ag/hf_activate_voice_recognition function, introduce hfp_ag/hf_deactivate_voice_recognition instead
- HFP: merged legacy and enhanced Voice Recognition Activation (VRA) API. If available enhanced mode will be preferred.
- HFP: separate events for activation (HFP_SUBEVENT_VOICE_RECOGNITION_ACTIVATED) and deactivation (HFP_SUBEVENT_VOICE_RECOGNITION_DEACTIVATED) instead of combined HFP_SUBEVENT_VOICE_RECOGNITION_STATUS with status field. HFP_SUBEVENT_VOICE_RECOGNITION_ACTIVATED contains field "enhanced" to indicate if enhanced mode is used.
- HFP: enhanced VRA: HFP_SUBEVENT_VOICE_RECOGNITION_ACTIVATED is emitted after VRA is ready and the the audio connection is established. This simplifies HFP HF client logic, i.e. client can call `hfp_hf_enhanced_voice_recognition_report_ready_for_audio directly` upon reception of HFP_SUBEVENT_VOICE_RECOGNITION_ACTIVATED event.
- AVDTP: media config validator is called with preview of media codec configuration event and configured separately for sink/source
- AVRCP: use PANEL as default unit + subunit info
- AVRCP Controller: automatically query supported events when registering for notifications
- AVRCP Target: cache companies and events in library and remove need to answer query in application callback. Use Bluetooth SIG as default company.
- Run Loop: new functionality for HCI transport drivers and inter-process communication:
  - *btstack_run_loop_poll_data_sources_from_irq*: used to transfer control from IRQ handler to main thread/run loop
  - *btstack_run_loop_execute_on_main_thread*: schedule code execution on main thread from other thread
  - *btstack_run_loop_trigger_exit*: trigger run loop exit
- POSIX / Windows / Raspi / Qt: use updated ctrl-c handling
- POSIX TLV: use max value size of 2048, assert in store function if value size is larger


## Release v1.4.1

### Added
- GAP: emit GAP_EVENT_PAIRING_STARTED and GAP_EVENT_PAIRING_COMPLETE

### Fixed
- GAP: store link key in hci connection struct to allow authenticate after pairing without bonding
- GAP: avoid requesting authentication twice
- GAP: cache own address on start advertising and connecting, provide getters
- GAP: stop LE connecting if create connection fails (e.g. connectable adv active and multiple roles not supported)
- SM: fix race condition between local address changes and pairing procedure
- ATT DB: fix spelling `gatt_server_get_handle_range_for_service_with_uuid128`, `gatt_server_get_handle_range_for_service_with_uuid16`

### Changed
- HCI: update advertising data without stopping advertising first
- GAP: Drop local bonding flag in IO Capability Reply if remote does not indicate bonding
- GAP: return status for `gap_set_security_mode`
- GAP: abort legacy pairing if Level 4 is required
- GAP: abort SSP on IO Capabilities Request event if Level 4 is required but SC not supported by remote
- GAP: abort SSP on User Confirmation Request event if Level 3 is required but MITM protection not possible
- GAP: validate minimal service security level can be reached during pairing in responder role
- L2CAP: don't trigger hci disconnect if l2cap security requirements are insufficient
- CVE-2020-26555: reject connections to and from devices with same BD ADDR
- CVE-2020-26555: ignore NULL link key
- CVE-2020-26558: abort LE Secure Connection pairing if remote uses the same public key

## Release v1.4

### Added
- HCI: `btstack_transport_sco.h` supports SCO over physical PCM/I2S interface (`HAVE_SCO_TRANSPORT`)
- POSIX: `btstack_transport_sco_i2s_test_bridge.c` implements SCO transport interface for UART-to-I2S test bridge
- btstack_uart: `btstack_uart_t` interface extends `btstack_uart_block_t`:
  - support sending and receiving SLIP frames for HCI H5
  - support odd parity
  - `hci_transport_h4` and chipset drivers have new functions to provide `btstack_uart_t`
- btstack_uart_slip_wrapper: wrapper that implements SLIP functionality for existing `btstack_uart_block` drivers.
- hci_transport: add parity field and pass on to `btstack_uart_t` in h4 and h5
- GATT Client: Battery Service Client
- GATT Client: Device Information Service Client
- GATT Client: HID-over-GATT (HOG) Client, Report and Boot Host
- GATT Client: Scan Parameters Service Client
- GATT Server: Scan Parameters Service Server
- GAP: support scan page configuration with `gap_set_page_scan_activity` and `gap_set_page_scan_type`
- GAP: support sniff subrating with `gap_sniff_subrating_configure`
- GAP: support QoS setup with `gap_qos_set`
- AVRCP: new field `button_pressed` in `AVRCP_SUBEVENT_OPERATION`
- AVRCP: `AVRCP_SUBEVENT_OPERATION` emitted for button release
- AVRCP Controller: `avrcp_controller_start_press_and_hold_cmd` supports arbitrary device buttons
- AVRCP Controller: reassemble fragmented AVCTP packets
- AVDTP: `avdtp_register_media_config_validator` allows to validate media codec configuration
- A2DP Source: `ENABLE_A2DP_SOURCE_EXPLICIT_CONFIG` disables auto config. requires call to `a2dp_source_set_config_{CODEC}`

### Fixed
- GAP: calculate IO Cap AuthReq Bondable Mode based on `gap_ssp_set_authentication_requirement` and `gap_set_bondable_mode`
- GAP: only store link key for SSP if remote side has set bondable in io cap auth requirements
- GAP: allow to disable link supervision timeout
- GAP: fix `gap_connect` after `gap_connect_cancel`
- GAP: re-configure advertisements after power cycle
- HCI: handle start inquiry failure
- L2CAP: fix create outgoing connection triggered from packet handler on hci disconnect event
- L2CAP: return unknown mandatory option in config response
- AVDTP: fix spelling `avdtp_set_preferred_sampling_frequency`
- AVRCP Target: fix notification changed event
- HFP: Emit audio connection released on SLC Release, e.g. on remote power off
- HFP HF: fix audio connection setup if codec negotiation is supported
- HFP HF: only emit single event for RING and AG Status updates
- HFP AG: fix audio connection setup for in-band ringtone on incoming connection

### Changed
- Port Archive: moved ports that are not recommended for new designs to port/archive folder:
  - MSP430: the ports used the older community GCC version without 20-bit support needed for code size > 64kB
  - Broadcom/Cypress H5: uploading PatchRAM is only possible in H4 mode. It's better to also use H4 in general
  - PIC32-Harmony: the port used Harmony v1 while Harmony v3 has been out since a while
  - iOS: not supported
- Run Loop Base: functionality used in most platform run loop implementations
  - code from `btstack_run_loop_base.c` moved into `btstack_run_loop.c` to minimize changes to build systems
  - `btstack_run_loop_base.c` is a placeholder and can be removed from build
- HCI Dump: replace monolithic `hci_dump.c` (with many #ifdefs) into dispatcher with platform-specific implementations:
  - `posix/hci_dump_posix_fs` - writes binary log file
  - `posix/hci_dump_stdout` - log to console using printf with local system time
  - `embedded/hci_dump_embedded_stdout` - log to console using printf
  - `embedded/hci_dump_segger_stdout` - log to RTT console using `SEGGER_printf`
  - `embedded/hci_dump_segger_binary` - writes binary log over RTT to host
- HCI: config I2S for BCM Controllers if `ENABLE_SCO_OVER_PCM`, reduce bit clock to 256/512 kHz
- btstack_uart_posix: supports SLIP frames and replaces `btstack_uart_block_posix`
- hci_transport_h5: more performant H5 implementation that requires `btstack_uart_t` driver with SLIP support
- POSIX Ports: use new `btstack_uart_posix` implementation
- posix-h5/posix-h5-bcm: use even parity for UART
- HCI Transport: extract convenience function declaration for h4, h5, em9304_spi, and usb into separate hci_transport_{type}.h
- GAP: provide Device ID from EIR in GAP_EVENT_INQUIRY_RESULT
- GAP: only store link key if it allows requested security level
- GAP: abort SSP pairing if MITM protection required but not possible
- SM: start pairing as Central for already encrypted connection on Slave Security Request
- GATT Client: Use ATT_READ_REQUEST for first blob of Read Long Characteristic and Read Long Characteristic Descriptor
- GATT Server: Allow ATT Read Callback to return custom ATT Error Code
- Nordic SPP Service Server: use `GATTSERVICE_SUBEVENT_SPP_SERVICE_CONNECTED` and `GATTSERVICE_SUBEVENT_SPP_SERVICE_CONNECTED`
  events instead of callback, and `RFCOMM_DATA_PACKET` for received data
- u-blox SPP Service Server: use `GATTSERVICE_SUBEVENT_SPP_SERVICE_CONNECTED` and `GATTSERVICE_SUBEVENT_SPP_SERVICE_CONNECTED`
  events instead of callback, and `RFCOMM_DATA_PACKET` for received data
- HID: Move `src/classic/hid.h` into `src` and prefix with `btstack_` to use it with BLE and avoid name clashes
- HFP: provide acl_handle in events to identify connection
- HSP AG: emit HSP_SUBEVENT_BUTTON_PRESSED instead of audio connection setup/release
- Example: use `btstack_event.h` getters instead of direct array access, use enum to compare status codes


## Release v1.3.2

### Added
- GAP: support for Classic Out-of-Band (OOB) pairing via `gap_ssp_remote_oob_data` with `ENABLE_CLASSIC_OOB_PAIRING`
- GAP: read local OOB data on start and on call to `gap_ssp_generate_oob_data`, provided via `GAP_EVENT_LOCAL_OOB_DATA`
- HID Host: add profile, update `hid_host_demo.c` example

### Fixed
- L2CAP: make handling of HCI disconnect more robust
- AVDTP: emit stream release for active stream if signaling connection is closed first, e.g. caused by HCI disconnect
- AVRCP: fix issue when Controller and Target send at the same time

### Changed
- A2DP, AVDTP: use `a2dp_source_set_config_{TYPE}` and `avdtp_config{TYPE}_store` to avoid large number of parameters


## Release v1.3

### Added
- CC256x: with ENABLE_CC256X_ASSISTED_HFP, HFP enables WBS codec on demand and configures PCM/I2S interface for 8kH/16kHz
- BCM: with ENABLE_BCM_PCM_WBS, HFP enables WBS codec on demand and configures PCM/I2S interface for 8kH/16kHz
- SDP Client RFCOMM: add `sdp_client_query_rfcomm_channel_and_name_for_service_class_uuid`
- HFP: `ENABLE_HFP_AT_MESSAGES` lets HFP emit  `HFP_SUBEVENT_AT_MESSAGE_SENT` and `HFP_SUBEVENT_AT_MESSAGE_RECEIVED`
- A2DP, AVDTP: provide capabilities and configuration events for A2DP codecs: SBC, MPEG Audio, MPEG AAC, ATRAC
- A2DP + AVDTP Source: allow to send media packet with `avdtp_source_stream_send_media_packet` and `a2dp_source_stream_send_media_packet`
- A2DP + AVDTP Source: add `avdtp_source_stream_send_media_payload_rtp` and `a2dp_source_stream_send_media_payload_rtp`
- A2DP Source: emit `A2DP_SUBEVENT_SIGNALING_CAPABILITIES_COMPLETE`
- A2DP Source: allow to configure endpoints by calling `a2dp_source_set_config_{TYPE}` during SEP discovery with SBC fallback

### Fixed
- HCI: keep `le connecting request` on connection complete active, fixes gap_auto_connection_stop() + gap_auto_connection_start()
- L2CAP: fix packet size check for incoming classic basic channels (regression introduced in v1.2.1)
- HFP AG/HSP AG: avoid connecting to remote service with same role
- A2DP Source: support multiple Stream Endpoints with different Media Codec types
- A2DP Source: emit codec configure event with reconfigure flag set on reconfigure
- GATT Compiler: support multiple instances of the same service

### Changed
- GAP: provide Link Type parameter to incoming connection filter for `gap_register_classic_connection_filter`
- HFP/GOEP Client/AVDTP/A2DP: return `SDP_SERVICE_NOT_FOUND` if no suitable SDP record is found
- AVDTP Source: `avdtp_source_stream_send_media_payload` includes SBC Header and was deprecated
- AVDTP/A2DP: use `avdtp_channel_mode_t` in `A2DP_SUBEVENT_SIGNALING_MEDIA_CODEC_SBC_CONFIGURATION`
- A2DP: fix events and use `a2dp_cid`, `local_seid,` `remote_seid` field names in A2DP sub-events
- GATT Client: Skip MTU exchange after MTU exchange on ATT Server
- Ports: STM32-F103RB Nucleo + CC256x port removed
- ESP32: enabled HFP Wide-Band Speech, disable classic secure connections in HSP/HFP demos


## Release v1.2.1

### Fixed
- L2CAP: use connection handle for channel lookups
- L2CAP: forward data only in open state

### Changed
- L2CAP: check packet size against local mtu for classic basic channels


## Release v1.2

### Fixed
- L2CAP: trigger pairing for outgoing LE Data Channels if security level insufficient
- SM: fix update of sc flag for re-encrypted connection in peripheral role
- SM: send security request on re-connect if bonded and `ENABLE_LE_PROACTIVE_AUTHENTICATION` is defined
- ESP32: fix audio sink driver

### Added
- GAP: `gap_delete_bonding` removes device from LE Resolving List and from discards LE bonding information
- GATT Client: delete bonding information if re-encryption fails and `ENABLE_LE_PROACTIVE_AUTHENTICATION` is not defined
- GATT Client: gatt_client_set_required_security_level() allows to set required minimum security level for all GATT requests
- SM: emit events for re-encryption started/complete when bonding information is available

### Changed
- AVRCP Controller: allow to send multiple absolute volume commands without waiting for response.
- GAP: replaced `ENABLE_LE_CENTRAL_AUTO_ENCRYPION` with `ENABLE_LE_PROACTIVE_AUTHENTICATION`


## Changes October 2020

### Fixed
- AVDTP Initiator: avoid use of remote seid for stream endpoint lookup, fixes issue with two connected devices
- AVDTP Source: buffer for SBC media codec information got discarded, leading to invalid Set Configuration command in second connection
- SM: only trigger Cross-Transport Key Derivation (CTKD) when bonding is enabled
- SM: set LinkKey flag to request CTKD if enabled
- SM: store CTKD key with Public Identity Address
- SM: only allow CTKD to overwrite existing link key if derived key has same or higher authentication
- SM: start SMP Timeout when sending Security Request
- HFP HF: fix response to AG Codec Selection while waiting for OK of parallel command
- HCI: fix reject of LE remote connection param request via HCI

### Added
- GAP: add `gap_get_link_key_for_bd_addr`
- GAP: add `gap_bonded` to check if bonding information is available for active connection
- SM: support h7 for CTKD

### Changed
- SM: Cross-Transport Key Derivation requires `ENABLE_CROSS_TRANSPORT_KEY_DERIVATION` now
- SM: block connection if encryption fails for bonded devices as Central
- SM: support pairing as Central after failed re-encryption


## Release v1.1

### Fixed
- AVRCP/AVCTP: report AVRCP 1.6 and AVCTP 1.4 in SDP record

### Added

### Changed


## Changes September 2020

### Fixed
- HFP: fix parsing of ranges e.g. in +CIND responses
- AVDTP, AVRCP: fix bugs due to transaction id overrun
- A2DP Source: fix issues with stream configuration by sink
- hci_dump: fix tv_us calculation for non-posix / embedded systems with binary output

### Added
- `btstack_ring_buffer`: add `btstack_ring_buffer_reset` to reset it to initial state/empty
- GAP: Support for address resolution of resolvable private addresses by Controller with `ENABLE_LE_PRIVACY_ADDRESS_RESOLUTION`

### Changed
- AVDTP, AVRCP, HSP: schedule SDP query, avoids avoids 'command disallowed' if SDP client is busy
- HSP, HFP: allow to configure usable SCO packet types
- cc256x: update CC256xC init script to v1.4
- A2DP Source: use Get All Capabilities if supported by remote get Delay Reporting capability

## Changes August 2020

### Fixed
- ESP32: fix authentication for incoming Secure Connections
- AVDTP: Fix forwarding of Delay reports
- STM32-F4Discovery: fix pan_lwip_http_server by increasing HCI_ACL_PAYLOAD_SIZE
- tool/create_packet_log: basic support for 16-bit Unicode log files from Windows

### Added
- `btstack_run_loop_base`: added `btstack_run_loop_base_dump_timer`
- GAP: request role change for classic connection via `gap_request_role`
- GAP: LE Whitelist API with `gap_le_whitelist_x` with x = add, remove, clear and new `gap_connect_with_whitelist`
- SDP Client: add sdp_client_register_query_callback() allows to register query request instead of polling sdp_client_ready()
- BNEP lwIP: add `bnep_lwip_connect` to establish BNEP connection and manage lwIP network interface
- New `btstack_linked_queue` utility, a linked list-based queue with first-in-first-out semantics and constant time enqueue/dequeue operations
- btstack_tlv_posix: add `btstack_tlv_posix_deinit`
- New `btpclient` for use with [auto-pts project](https://github.com/intel/auto-pts)

### Changed
- GAP: treat AES-CCM encrypted connection as mutually authenticated (BIAS)
- GAP: 'gap_auto_connect_x' API deprecated. Please directly manage LE Whitelist with `gap_le_whitelist_*` functions and call `gap_connect_with_whitelist` instead
- example/hid_host_demo: try to become master for incoming connections
- btstack_run_loop: use btstack_assert instead of local while(true)
- att_db_util: allow to reset att_db via `att_db_util_init`

## Changes July 2020

### Fixed
- AVDTP: fix invalid response for Get Capabilities request if Delay Reporting was supported
- AVDTP: handle concurrent signaling establishment with reject and retry

### Added
- example/hid_host_demo: support reconnect from HID device
- Crypto: support software AES128 for AES-CCM operations
- AVRCP: introduced AVRCP_FEATURE_MASK_* as alternative to avrcp_controller_supported_feature_t and avrcp_target_supported_feature_t enums
- btstack_audio: add set_volume() to sink and set_gain() to source interfaces, minimal volume control for portaudio playback
- AVDTP: renamed definition of supported features from AVDTP_SOURCE_SF_ and AVDTP_SINK_SF_ to AVDTP_SOURCE_FEATURE_MASK_ and AVDTP_SINK_FEATURE_MASK_ respectively
- GAP: Provide gap_get_role to query master/slave role for HCI connection handle
- GAP: Provide gap_pin_code_response_binary to use binary data as PIN, e.g. for pairing with Nintendo Wii Remote

### Changed
- GAP: set minimum required encryption key size for Classic connections back from 16 to 7, matching the Core spec


## Changes June 2020

### Fixed
- HFP: Fix parsing of empty fields, e.g. phone number in +CLCC and other AT commands
- SM: Fix validation of confirm value for secure connection Passkey entry
- AVRCP: handle concurrent signaling establishment with reject and retry

### Added
- GAP: Detect Secure Connection -> Legacy Connection Downgrade Attack by remote features and actual encryption type (BIAS)
- GAP: Mutual authentication: request authentication after Classic connection got encrypted (BIAS)
- Windows port for Dialog DA14585 connected via serial port

## Changes
- CVSD PLC: treat zero frames as good and allow to mark data as bad, e.g. if reported by Controller as erroneous

## Changes May 2020

### Fixed
- hfp_hf, hsp_hs: use eSCO params in accept sco connection only for incoming eSCO connections
- pbap_client: fix PBAP UUID len on connect message
- SM: fix secure connection pairing as peripheral when local user confirmation happens after remote one
- A2DP Source: only connect to remote sink stream endpoints
- btstack_hal_flash_memory: fix write of 0xff bytes to simulated flash
- hsp_hs: fix disconnect if audio not connected
- hsp_ag: fix accept incoming connection

### Added
- example/le_mitm: MITM implementation that forwards ATT PDUs and allows for pairing
- GAP: gap_set_security_level sets required security level for incoming and outgoing connections
- cc256x: allow to specify power vector for each modulation type
- FreeRTOS: btstack_run_loop_freertos_trigger_exit allows to request run loop exit
- SM: support LE Secure Connections Only mode with sm_set_secure_connections_only_mode
- GAP: enable BR/EDR Secure Connections if supported, add gap_secure_connections_enable

### Changed
- L2CAP ERTM: send extended features request only once per HCI connection


## Changes April 2020

### Fixed
- hog_mouse_demo/hog_keyboard_demo: handle set protocol mode = boot protocol mode
- HCI: only update BD_ADDR placeholder in shortened and complete name in EIR data, limit device name to 240/248 bytes

### Added
- GAP: gap_set_allow_role_switch allows to prevent role switch in outgoing classic ACL connections
- example: hog_boot_host_demo implements an HID-over-GATT Boot Host that supports keyboard and mouse
- HCI: add ENABLE_LE_LIMIT_ACL_FRAGMENT_BY_MAX_OCTETS that forces fragmentation of ACL-LE packets to fit into over-the-air packet

### Changed
- Broadcom/Cypress: wait 300 ms after PatchRAM update in hci.c to assert Controller is ready
- esp32: provide esp-idf/component/btstack/btstack_port_esp32.c and only minimal app_main in template/main/main.c
- att_db: skip att_read_callback for ATT Read Blob Request if offset == value_len


## Changes March 2020

### Fixed
- GAP: fixed gap_set_scan_parameters() if issued right before gap_start_scan()
- HCI: only send HCI Read Local Encryption Key Size if supported by Controller

### Added
- GATT Client: allow to register for any notification/indication and/or any connection
- HCI: added hci_read_inquiry_scan_activity and hci_write_inquiry_scan_activity commands
- chipset: assert hci packet buffers are suitable for firmware upload or patches (atwilc3000,bcm,cc256x,intel)
- btstack_util: added btstack_replace_bd_addr_placeholder

### Changed
- AVRCP Target: volume in avrcp_target_volume_changed is reported as current value in interim response to register for volume change notifications
- SDP Client: query attributes 0x0000..0xffff instead of 0x0001..0xffff to match other stacks / improve compatibility with bad sdp server implementations


## Changes Februar 2020

### Fixed
- AVRCP Target: fix reporting of PLAYBACK_STATUS_CHANGED
- HCI: handle reconnect request for Classic and LE connections triggered by packet handler for Disconnection Complete Event

### Changed
- hid_host_mode: allow sniff mode

### Added
- port/qt-usb and port/qt-h4: integrate BTstack Qt run loop for Unix- and Win32-based Qt application connected to Bluetooth module via H4 over serial port or USB


## Changes January 2020

### Fixed
- L2CAP ERTM: avoid read-after-free on decline of incoming connection
- GATT Client: set uuid16 to zero when deserializing uuid128 services, characteristics, and descriptors
- att_db_util: fix realloc of att db buffer for large attributes
- btstack_tlv_posix: only keep last value in memory, fix delete operation
- l2cap_signaling: use packet boundary flags 0x00 for LE signaling packets (ignoring hci_non_flushable_packet_boundary_flag_supported())

### Added
- att_db_util: provide GATT Database Hash via att_db_util_hash_calc
- GATT Compiler: provide GATT Database Hash via GATT_DATABASE_HASH Characteristic
- ATT Server: validate request pdu length

### Changed
- Crypto: update AES-CMAC implementation to access all message bytes sequentially


## Changes December 2019

### Fixed
- example/pan_lwip_http_server: use Network Access Point, CoD
- sm: emit pairing complete in master role when no keys are distributed / bonding disabled

### Added

### Changed
- Updated CC256x initscript: CC256xC v1.3
- ESP32: add CMake project files


## Changes November 2019

### Fixed
- AVDTP Source: return correct `avdtp_cid` and `local_seid` in `AVDTP_SUBEVENT_STREAMING_CAN_SEND_MEDIA_PACKET_NOW`
- L2CAP: send LE Data Channel SDUs round robin with other data
- L2CAP ERTM: send ERTM I-frames round robin with other data

### Added
- ATT Server: return error if request to send now for Notification or Indication already registered
- Linked List: return if item was added for `btstack_linked_list_add[_tail]`
- btstack_run_loop_remove: return bool true if timer/data source was removed
- segger-rtt: allow to configure with `SEGGER_RTT_PACKETLOG_*` directives, update to v6.54
- GAP: support setting Link Supervision Timetout for outgoing Classic connections using `gap_set_link_supervision_timeout`
- lwip: add download test files to http server demo

### Changed
- Linked List: return bool true if item was removed


## Changes October 2019

### Fixed

### Added
- `btstack_bool.h`: provide boolean type 'bool' via `<stdbool.h>` or as backport
- provide `btstack_assert(condition)`
- H4 Transport: avoid calling `hci_transport_h4_trigger_next_read` when transport is closed

### Changed
- libusb and posix ports: store bonding information in TLV


## Changes September 2019

### Fixed
- L2CAP ERTM: assert that packet can be stored in fragment buffers in ertm
- L2CAP ERTM: reject incoming connection if ERTM is configured as mandatory but not supported by remote
- GATT Client: allow Write Without Response independent of other requests

### Added
- GAP: allow to reject GAP classic connection via gap_register_classic_connection_filter
- GAP: support reading RSSI for Classic+LE using gap_read_rssi. Emits `GAP_EVENT_RSSI_MEASUREMENT`

### Changed
- Bluetooth and BTstack Error Codes and Events: collect status codes in bluetooth.h and events in btstack_defines.h
- bluetooth.h: extract internal defintitions to respective protocol layers
- Updated CC256x initscripts (CC256xB v1.8, CC256xC v1.2, CC256xC v1.2)


## Changes August 2019

### Fixed
- POSIX, WICED, Windows, FreeRTOS run loops: handle time_ms overrun after 49 days
- RFCOMM: accept incoming L2CAP connection in Basic mode if ERTM is enabled but not requested for this connection
- RFCOMM: limit RFCOMM MTU by local L2CAP MTU for outgoing connections (only revelvant for ERTM)
- L2CAP ERTM: stop timers on disconnect
- L2CAP ERTM: fix sending of segmented SDUs
- L2CAP ERTM: handle unsupported Information Response
- SM: generate local nonce for confirm value in JW+NC+PK in Secure Connections Responder role

### Added
- `btstack_run_loop_base`: portable implementation of timer and data source management as base for platform specific implementations

## Changed
- FreeRTOS: use xQueueCreateStatic (static variant of xQueueCreate) if available for static memory-only setups
- L2CAP ERTM: handle invalid Information Response (assume no extended features supported)
- POSIX: use monotonic clock as timebase if available
- HCI Transport H4/H5/EM9304 SPI: ignore block read/sent from UART driver when closed
- HCI: Read Encryption Key Size after encryption was enabled
- Errata 11838:
  - GAP: gap_set_required_encryption_key_size allows to set the required key size, default = 16 (max)
  - GAP: validate encryption key size to emit GAP Security Levels

## Changes July 2019

### Fixed
- SM: Fixed regression introduced in f3582630
- L2CAP: avoid reading l2cap signaling command len out of bounds
- HCI Transport H4/H5/EM9304 SPI: fix payload size checks (also for 8/16-bit platforms)

### Changed
- SM: Start encryption upon receiving slave securiy request if bonded
- hci: use 2 as HCI_INCOMING_PRE_BUFFER_SIZE in LE-only configuration for GATT Client

---

## Changes June 2019

### Changed
- FreeRTOS: use freertos/.. prefix to include FreeRTOS headers if HAVE_FREERTOS_INCLUDE_PREFIX is defined
- BNEP: add Connection Handle to BNEP_EVENT_CHANNEL_OPENED
- Examples: renamed le_counter to gatt_counter and le_streamer to le_streamer_server to indicate suppport for GATT over BR/EDR

### Fixed
- BNEP: Bluetooth address is stored in little-endian format for all BNEP_EVENT_*
- libusb: avoid use-after-free for SCO packets on disconnect

### Added
- example: pan_lwip_http_server using lwIP as network stack to implement PAN NAP service
- platform/lwip/bnep_lwip.c: BNEP lwIP adapter that forwards packets between BNEP service and lwIP
- ENABLE_GATT_OVER_CLASSIC enables support for GATT over BR/EDR in att_server

---

## Changes May 2019

### Changed
- ESP32: Configure SCO over HCI after power up
- btstack_tlv_flash_bank: support targets where a value cannot be overwritten with zero. When ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
  is defined, an explicit delete field is used to indicate an invalid entry.

### Fixed
- SM: Avoid potential use-after-free on immediate disconnect (lookup connection via con handle instead of storing pointer)

### Added
- gatt_client: emit query complete event for signed write operation
- hci_transport_h4: add workaround for flow control bug in CYW2070x, enable with ENABLE_CYPRESS_BAUDRATE_CHANGE_FLOWCONTROL_BUG_WORKAROUND

---

## Changes April 2019

### Changed
- ESP32: use micro-ecc from 3rd-party as esp-idf removed it in their 3.3 release

### Fixed
- hci: pad LE Scan response with zeroes
- SM: store local CSRK
- ATT DB: call write callback for validated signed writes
- ATT Server: abort signed write validation on incoming new request
- Bluetooth SIG web scraping tools updated
- libusb: compiles for FreeBSD

### Added

---

## Changes March 2019

### Changed
- use Makefile for stm32-f4discovery-cc256x port
- le_device_db: add secure_connection argument to le_device_db_encryption_set and le_device_db_encryption_get

### Fixed
- SM: Use provided authentication requirements in slave security request

### Added
- port/stm32-f4discovery-cc256x: add support for built-in MEMS microphone
- SM: Track if connection encryption is based on LE Secure Connection pairing
- ATT DB: Validate if connection encrypted is based on SC if requested
- att_db_util: support ATT_SECURITY_AUTHENTICATED_SC permission flag
- GATT Compiler: support READ_AUTHENTICATED and WRITE_AUTHENTICATED permsission flags
- ESP32: erase nvs flash is newer nvs version found
- libusb: add support for nRF52840-PCA10056 running Zephyr hci_usb example
- port/stm32-l073rz-nucleo-em9304 for Nucleo L073RZ with EM9304 DVK, replaces port/stm32-l053r8-nucleo-em9304

## Changes February 2019

### Changed
- example/a2dp_sink_demo: use linear resampling to fix sample rate drift
- btstack_audio: split interface into sink and source

### Fixed
- Crypto: fix lockup when stack is shutdown while waiting for result of HCI Command, e.g. LE Read Local P256 Public Key
- SM: Avoid SM_EVENT_PAIRING_COMPLETE with ERROR_CODE_REMOTE_USER_TERMINATED_CONNECTION after successful pairing in responder role

### Added
- example/a2dp_sink_demo: add target role, support volume control on both devices
- example/audio_duplex: playback audio audio source on audio sink (test audio path)
- btstack_audio_embedded: implement audio source path

---

## Changes January 2019

### Changed
- L2CAP: provide channel mode (basic/ertm) and fcs option in L2CAP_EVENT_CHANNEL_OPENED
- RFCOMM: support L2CAP ERTM. Callbacks passed to rfcomm_enable_l2cap_ertm() are used to manage ERTM buffers

### Added
- L2CAP: emit L2CAP_EVENT_ERTM_BUFFER_RELEASED if ERTM buffer not needed/used anymore
- L2CAP: add fcs_option to ERTM config l2cap_ertm_config_t
- HCI: validate advertisement data length field when generating GAP_EVENT_ADVERTISING_REPORT
- ad_parser: validate data element length fields in ad_iterator_has_more
- Raspberry Pi 3 A+/B+ port in port/raspi, starts without power cycle

### Fixed
- HCI: release outgoing buffer on disconnect if waiting to send another ACL fragment
- POSIX: use correct baudrate enums for baud rates higher than 921600 (Linux)
- Crypto: directly process queued crypto operation on HCI result

---

## Changes December 2018

### Added
- SM: generate and store ER / IR keys in TLV, unless manually set by application
- hci_dump: support PacketLogger or BlueZ format output via SEGGER RTT Channel 1 Up

### Fixed
- SM: fix internal buffer overrun during random address generation

## Changes November 2018

### Added
- GAP: gap_le_connection_interval provides connection interval for conn handle
- Nordic SPP Service Server: GATT service that emulates a serial port over BLE based on Nordic Semiconductor documentation.
- uBlox  SPP Service Server: GATT service that emulates a serial port over BLE based on uBlox documentation.
- SM: ENABLE_LE_CENTRAL_AUTO_ENCRYPTION triggers automatic encryption on connect to bonded devices
- SM: generate and store ER / IR keys in TLV, unless manually set by application

### Fixed
- SM: prevent random address updates if gap_random_address_set was used
- SM: fix internal buffer overrun that can cause storing of bonding information to fail
- SM: ignore Slave Security Request after sending own Pairing Request
- L2CAP: fix use after free on disconnect if ERTM is enabled
- HFP: Handle multiple commands/responses in single RFCOMM packet
- Memory Pools: clear all buffers before use

---

## Changes October 2018

### Added
- SDP Server: queue incoming connections when already connected instead of rejecting them
- GAP: Support enter/exit sniff mode via gap_sniff_mode_enter/exit. gap_set_default_link_policy_settings is needed to enable sniff mode in general.
- HIDS Device: GATT service that exposes HID reports intended for HID Devices, like keyboard and mouse.

### Fixed
- HCI: fix bug in gap_inquiry_stop that triggered additional GAP_EVENT_INQUIRY_COMPLETE instead of stopping the inquiry
- L2CAP: fix issue with outgoing connection before read remote supported complete when other channels exist
- L2CAP ERTM: allow SDU of szie MPS in first packet that contains L2CAP SDU Length
- L2CAP ERTM: fix memory corruption triggered if local_mtu > mps
- L2CAP ERTM: fix outgoing fragment management
- HFP: decline incoming RFCOMM connection after outgoing connection was started
- AVRCP: fix crash on disconnect of connection established by remote

---

## Changes September 2018

### Fixed
- HCI: Error creating outgoing connection (e.g. Connection Limit Exceeded) now handled
- L2CAP: Error creating outgoing connection (e.g. Connection Limit Exceeded) now handled
- L2CAP: Evaluate 'can send now' on HCI Disconnect as ACL buffers in Bluetooth Controller have been used for the closed connection are freed implicitly
- L2CAP: Check can send now before sending extended information requeste needed for ERTM mode
- L2CAP: Use valid signaling identifier for L2CAP Connection Parameter Update Request
- RFCOMM: Trigger l2cap request to send on rfcomm credits when client is waiting to sendtrigger l2cap request to send on rfcomm credits when client is waiting to send
- RFCOMM: Avoid use-after-free on channel finalize
- GATT Client: stop timer on disconnect - fixes use after free / crash

### Added
- A2DP Source: Support stream reconfiguration (a2dp_source_reconfigure_stream_sampling_frequency)
- 3rd-party: yxml is used for PBAP vCard list parsing
- cc256xC: new v1.1 init scripts

---

## Changes August 2018

### Added
- PBAP: added pbap_get_phonebook_size() to get phonebook entry count

### Fixed
- GATT Server: Allow enable Notifications/Indication with Write Command. Fixes issue with some Android devices.
- SM: fix pairing for Secure Connections with Bonding if remote sends additional keys
- SM: drop LTK flag from Pairing Response for Secure Connections
- L2CAP: fix emitted L2CAP_EVENT_CONNECTION_PARAMETER_UPDATE_REQUEST

## Changes June 2018

### Added
- btstack_audio.h: application level API for audio playback and recording
- embedded/hal_audio.h: low-level API for audio playback and recording
- HID Device: hid_device_connect(..) function
- ESP32: implement hal_audio
- DA14585: support for Dialog Semiconductor DA14585 LE-only controller
- Raspberry Pi 3 + Raspberry Pi Zero W port in port/raspi

### Changed
- Errata 10734:
  - SM: Generate new EC Public Keypair after each pairing
  - SM: Abort failure with DHKEY_CHECK_FAILED if received public key is invalid (instead of unspecified error)
- btstack.h: only include classic headers if ENABLE_CLASSIC is defined
- windows: ignore virtual Bluetooth adapter provided by VMware
- Replaced HCI_PACKET_BUFFER_SIZE with HCI_INCOMING_PACKET_BUFFER_SIZE and HCI_OUTGOING_PACKET_BUFFER_SIZE

---

## Changes June 2018

### Fixed
- HFP: Fix Wide Band Speech bit in SDP record for both HF/AG. Missing bit prevents macOS from using mSBC
- ATT Server: send ATT_EVENT_HANDLE_VALUE_INDICATION_COMPLETE with status ATT_HANDLE_VALUE_INDICATION_DISCONNECT on disconnect
- AVRCP Controller: fix parsing of now playing info

### Changed
- ATT Server: ATT_HANDLE_VALUE_INDICATION_DISCONNECT is delivered to service handler if registered

### Added
- ATT Server: packet handler field added to att_service_handler_t to receive: connect/disconnect, atu exchange, indication complete

---

## Changes May 2018

### Added
- GAP: re-encrypt outgoing connection if bonded
- ATT Server: wait until re-encryption is complete
- GATT Client: wait until re-encryption is complete
- ATT Server: added att_server_request_to_send_notification and att_server_request_to_send_indication
- GATT Client: if ENABLE_GATT_CLIENT_PAIRING, GATT Client starts pairing and retry operation on security error

### Changed
- ATT Server: att_server_register_can_send_now_callback is deprecated, use att_server_request_to_send_notification/indication instead

### Fixed
- SM: Fix LE Secure Connection pairing in Central role
- le_device_db_tlv: fix seq nr management
- SM: improve le_device_db lookup and storing of IRK
- GATT Server: fix lookup for Client Characteristic Configuration in services with multiple Characteristics
- RFCOMM: emit channel closed on HCI/L2CAP disconnect after sending DISC while expecting UA

---

## Changes April 2018

### Added
- Crypto: btstack_crypo.h provides cryptographic functions for random data generation, AES128, EEC, CBC-MAC (Mesh)
- SM: support pairing using Out-of-Band (OOB) data with LE Secure Connections
- Embedded: support btstack_stdin via SEGGER RTT

### Changed
- att_db_util: added security requirement arguments to characteristic creators
- SM: use btstack_crypto for cryptographpic functions
- GAP: security level for Classic protocols (asides SDP) raised to 2 (encryption)

### Fixed
- HFP: fix answer call command
- HCI: fix buffer overrun in gap_inquiry_explode
- SDP: free service record item on sdp_unregister_service

## Changes March 2018

### Added
- GAP: allow to limit number of connections in LE Peripheral role with gap_set_max_number_peripheral_connections
- ATT Server: support for delayed ATT read response, see example/att_delayed_read_response.c
- ATT Server: allow to specify security requirements seperately for read/writes. .h files need to be regenerated

### Fixed
- RFCOMM: fix infinite loop on L2CAP connection error (regression from 4c3eeed1)
- HSP HS: accept incomming SCO connection
- SM: fix iteration over LE Device DB entries for bonding and address resolving
- SM: store pairing information only if both devices have requested bonding

---

## Changes February 2018

### Added
- GATT Client: gatt_client_request_can_write_without_response_event() causes GATT_EVENT_CAN_WRITE_WITHOUT_RESPONSE
- SM: new event SM_EVENT_PAIRING_COMPLETE
- GAP: support iteration over stored Classic link keys: gap_link_key_iterator_init, gap_link_key_iterator_get_next, gap_link_key_iterator_done
- GAP: add gap_delete_all_link_keys

### Changed
- GATT Client: round robin for multiple connections
- ATT Dispatch: round robin for ATT Server & GATT Client
- L2CAP: round robin for all L2CAP channels (fixed and dynamic)
- btstack_link_key_db: addition functions for link key iteration
- GAP: LE scanning enabled not reset on HCI Reset -> can be enabled before HCI Power Up
- CSR: set all keys in psram instead of default

### Fixed
- tc3556x: fix startup after baud rate change

---

## Changes January 2018

### Added
- Port for Windows with Zephyr HCI Firmware connected via serial port
- em9304: upload patch containers during HCI bootup
- Makefile for STM32-F4Discovery port
- support for console out via SEGGER RTT
- LE Data Channels example in BTstack and [iOS example on GitHub](https://github.com/bluekitchen/CBL2CAPChannel-Demo)
- LE Streamer Client can send as fast as possbile as well
- L2CAP: option to limit ATT MTU via l2cap_set_max_le_mtu

### Changed
- HCI: allow to set hci_set_master_slave_policy (0: try to become master, 1: accept slave)
- GAP: gap_set_connection_parameters includes scan interval and window params
- GATT Client: GATT_EVENT_MTU indicates max MTU
- ATT DB Util: attribute handle is returned for new Services and Characteristics

### Fixed
- Windows: retry serial port operations if not all bytes have been read/written
- HFP: avoid buffer overflows setting up messages
- SBC Decoder: improved error handling for invalid SBC audio data
- GAP: fix Connection Parameter Response in Central role
- ATT DB Util: update pointer to database in case of realloc
- GATT Client: set UUID16 field if 16-bit UUID is stored as UUID128
- GAP: release HCI Connnection after gap_le_conne
- ATT: Exchanged MTU is propagate to ATT Server and GATT Client

---

## Changes December 2017

### Added
- Introduced btstack_network.h network interface abstraction
- btstack_network_posix implementation using Linux tun/tap interface
- WICED: support for btstack_stdin (HAVE_STDIN)
- GATT Server: Writes to GATT Client Characteristic Configuration are stored in TLV and restored on reconnect. The db.h file generated from db.gatt needs to be re-created.
- TLV: global TLV instance available via btstack_tlv_get_instance() (src/btstack_tlv.h)
- TLV: POSIX implementation that appends to a file on disk (platform/posix/btstack_tlv_posix.c
- LE Device DB TLV: overwrite oldest entry if no free entries available
- SM: allow to set fixed passkey in display role using sm_use_fixed_passkey_in_display_role
- Example/hid_host_demo with HID parser and support for basic US keyboard layout
- EM9304: custom HCI Transport implementation for EM9304 on top of btstack_em9304_spi.h platform abstraction only requires hal_em9304_spi.h to be implemented for new ports
- Port for Apollo2 MCU with EM9304 (ports/apollo2-em9304)

### Changed
- panu_demo: uses btstack_network.h now
- WICED: configure printf to replace Linefeed with CRLF
- SBC: split btstack_sbc_bludroid.c into seperate encoder and decoder implementations

### Fixed
- RFCOMM: support connection requests during connection failure
- L2CAP: support connection requests during connection failure
- L2CAP: fix default remote MTU as 672 instead of 48 (Minimal MTU)
- HCI: avoid double free during halting
- SM: fixed reconnect using legacy pairing in slave role