CMake generation is the process that generates build-ready files that could later be built by the build toolchain. It occurs on every CMake run. The process can be triggered directly by the user by running a cmake tool (such as cmake), or by the build toolchain when it detects changes in the source tree.

The input of a generation process is the generator to use. There's a variety of generators available, each having it's unique output type. For example, the Unix Makefiles generator will generate make-files, whereas the Ninja generator will generate ninja build files.

However, not all generators can be used on all OSs. While technically it's still possible and the output will be valid and "buildable", some generators just don't make sense to use on such platforms as there's no supported toolchain available for that OS. A good example is Microsoft Windows, as you'll read next.

The default generator on Microsoft Windows is the Visual Studio xx generator, where xx is a version of Visual Studio. It's equivalent to the C++ versions supported by the Microsoft Visual C++ Compiler. This generator creates Visual Studio solution files, which can later be used in the Visual Studio IDE and built by the Microsoft Visual C++ Compiler.

However, the Arduino toolchain is based on a derivative of the gcc compiler, which theoretically exists only for Unix systems. To use gcc on Windows, one should use toolchains like MinGW.

So to use the Arduino-CMake framework on Microsoft Windows, you'll need to be equipped with an appropriate toolchain and use one of the following generators:

• MSYS Makefiles - Generates MSYS make files
• Unix Makefiles - Generates standard UNIX make files
• MinGW Makefiles - Generates MinGW make files (best fit for Windows).
• Ninja - Generates ninja build files (Same as MinGW Makefiles but uses the ninja build tool instead)
• CodeBlocks - Unix Makefiles - Generates CodeBlocks project files (for the CodeBlocks IDE).
• Eclipse CDT4 - Unix Makefiles - Generates Eclipse CDT 4.0 project files (for the Eclipse IDE).

Even though it's probably the best generator to use on Microsoft Windows, it has a drawback which must be addressed before using it.

The MinGW generator encounters an error when the sh.exe binary exists in the System Path. In order to solve this issue, you should do the following:

1. Remove ${ARDUINO_SDK_PATH}/hardware/tools/avr/utils/bin from the System Path.

2. Run CMake with the following argument:

   -DCMAKE_MAKE_PROGRAM=${ARDIUNO_SDK_PATH}/hardware/tools/avr/utils/bin/make.exe
   

Then cmake will be generated as expected.