Install GNU ARM Toolchain
The STM32 uses a Cortex-M microprocessor from ST. To compile for this target, the “GNU ARM Embedded Toolchain” has to be installed. It can be found on the download page of the ARM developer website:
Choose the following version: Version 7-2017-q4-major
Start the installer by double-clicking the .exe file and follow the installation steps until you arrive to the screen below. Make sure the ‘Add path to environment variable’ checkbox is ticked:
NOTE!: Make sure that add path to environment variable is turned on after the installation.