Wemos LoLin32 clone with OLED
https://projetsdiy.fr/deballage-clone-wemos-esp32-lolin-ecran-oled-monochrome-ssd1306/


https://docs.espressif.com/projects/esp-idf/en/latest/security/secure-boot.html#signed-app-verify
https://docs.espressif.com/projects/esp-idf/en/latest/security/secure-boot.html#secure-boot-generate-key
https://docs.espressif.com/projects/esp-idf/en/latest/security/secure-boot.html#remote-sign-image

Board details:
  - Adruino 'Tools -> Board': WEMOS LOLIN32
  - OLED display wired differently use: SSD1306Wire  display(0x3c, 5, 4)

In Arduino preferences:
  - Additional Boards Manager URLs: https://dl.espressif.com/dl/package_esp32_index.json

Add extra libraries:
    $ cd /home/rick/Arduino/libraries
    $ git clone https://github.com/ThingPulse/esp8266-oled-ssd1306.git
    $ git clone https://github.com/arduino-libraries/NTPClient.git


Interesting cross-platform implementation
=========================================
  - https://freertos.org/index.html
  - https://aws.amazon.com/freertos/


ESP32 own toolchain has support for more resent features:
    https://dl.espressif.com/doc/esp-idf/latest/get-started/index.html#build-and-flash

https://exploreembedded.com/wiki/Overview_of_ESP32_features._What_do_they_practically_mean%3F
https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_manual_en.pdf
http://esp-idf.readthedocs.io/en/latest/api-guides/ulp_instruction_set.html


Issues
======
Onboard temperature sensor not working
--------------------------------------
    https://github.com/espressif/esp-idf/issues/146
    http://wiki.jackslab.org/ESP32_Onchip_Sensor


https://sigmdel.ca/michel/ha/rpi/add_mqtt_en.html
https://sigmdel.ca/michel/ha/domoticz/domoticz_add_mqtt_en.html