Arduino for STM32

Hey thanks for the response. Clearly I have a lot to learn, thanks for the links. The SKR-3 comes with Marlin so I know they have done some work on the variant already. Digging into their marlin branch, I found this variant file for the SKR-3 https://github.com/bigtreetech/SKR-3/blob/b5d842e9960893c...

I am trying to upload my own code to a BTT SKR 3 board, originally made for 3D printing. I thought it had everything I needed for my custom project. https://biqu.equipment/products/bigtreetech-btt-skr-3-control-board-for-3d-printer I am trying to upload some basic blink code to test it out but runni...