Compiling for Wemos D1 mini with Visual Studio Code
Intellisense reports &quot;Problems&quot; - these are distinct from compile time errors. Just because Intellisense can't resolve a literal or something doesn't mean it won't be resolved in the compiler; thus it's possible to have the IDE report a problem but still be able to have a successful compile. In the case described above, two changes to the c_cpp_properties.json file provided Intellisense with the information it needed. A header file was added to the forcedInclude section to provide pin definitions. A literal &quot;ESP8266&quot; was added to the defines section to indicate the processor type. This define is used in lots of header files so it must be know to Intellisense when reading the headers. Here are the relevant sections of that .json file:
        &quot;forcedInclude&quot;: [ 
            &quot;C:\\Users\\David\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\2.7.1\\variants\\d1_mini\\pins_arduino.h&quot;
        ],
        &quot;defines&quot;: [
            &quot;USBCON&quot;,
            &quot;ESP8266&quot;
        ],