- Allow control of enabling debug and debug level from IDE

- Make HardwareSerial::begin() and end() interrupt safe

- Put HardwareSerial and cbuf methods called from interrupt context in RAM

- Re-enable interrupts before directly enqueuing characters in the UART FIFO

- Add espduino board

- Rework StreamString::write to use String internal buffer directly (#1289)

- Add function to measure stack high water mark

- Update SDK to esp_iot_sdk_v1.5.0_15_12_15_p1

- Fix RAM corruption caused by our hook of register_chipv6_phy(init_data*).

- Optimize PWM interrupt handler for better precision

- Add warning levels configurable through Preferences

- Protect HardwareSerial's cbuf usage with InterruptLock

- SPIFFS: check if path length is valid (#1089)

- Set CPU frequency before running setup

- Add core_esp8266_features.h to be able to detect the features and libraries included in the ESP core

- Added ESPino to supported boards

- ESP8266HTTPClient: add CHUNKED encoding support (#1324)

- Fixed crash bug with mDNS where a string buffer could be used uninitialized

- Add WiFi TX power control

- Add WiFi sleep management

- Allow to hook into WiFi events from sketch

- Allow setting TCP timeout

- Add setSleepMode + getSleepMode and setPhyMode + getPhyMode to WiFi

- Update GDBStub library with the source of esp-gdbstub

- Servo: fix detach and attach

- ESP8266mDNS: refactoring, add TXT support

- Add HTTP Basic Auth to WebServer and libb64 (base64) to core

- Fix link-time dependency of ESP8266WebServer on SPIFFS (#862)

- Allow setting client side TLS key and certificate

- Replace chain of UDP pbufs with a single pbuf before sending (#1009)

- espota.py: add support for manually selecting ip and port for host side