My latest project is a rain gage that uses the WeMOS D1 Mini Pro. After minor software changes failed to compile, I quickly found that the reason was that all of the ESP8266 boards had disappeared from the list of boards. I went to Board Manager and reloaded the hardware list and tried to compile. I got the following error message: "error compiling for board LOLIN (WeMOS) D1 mini pro". This was preceded by the message "Board d1-mini-pro (platform ESP8266 package ESP 8266) is unknown". I get the same message when trying to compile code for my Sparkfun "Thing" and my Adafruit "Feather". The boards appear on the list of boards, but for some reason the IDE does not recognize them. I've tried everything I can think of, including uninstalling and re-installing the IDE (v. 1.8.9) and trying several older versions of the ESP8266 hardware files, but continue to get the error message. Any suggested solutions would be greatly appreciated.
The version of IDE on my second computer does not even show the ESP8266 board list when I call up the Board Manager. It is as though Arduino has stopped supporting 8266 boards.
rickir206:
This was preceded by the message "Board d1-mini-pro (platform ESP8266 package ESP 8266) is unknown".
The "Board ... is unknown" error occurs when a Boards Manager installation of a different version of a hardware package fails to completely uninstall the previous version. Here's how you solve it:
Click the link on the line following File > Preferences > More preferences can be edited directly in the file. This will open the Arduino15 (or similar name depending on OS) folder.
Navigate to the packages/esp8266/hardware/esp8266 folder.
You will see two folders. One is named by the version of the package you currently have installed, the other is named by the version of the package you previously had installed. Delete the folder with the previous version name. Please be very careful when deleting things on your computer. When in doubt back up!
rickir206:
The version of IDE on my second computer does not even show the ESP8266 board list when I call up the Board Manager.
rickir206:
It is as though Arduino has stopped supporting 8266 boards.
Arduino never supported ESP8266 boards. The support is provided by the 3rd party project ESP8266 core for Arduino. Arduino just provides a platform framework that allows any 3rd party to easily create hardware packages to add support for new hardware to the Arduino IDE.