We need a toolchain and library

Now that the connections and uploading have been dealt with, let’s turn to generating code. First of all, we need a C/C++ compiler: this one. GCC is now at version 5.0, but 4.8 is also fine (there have been some issues with 4.9 on ARM Cortex, it’s perhaps better to avoid that one…). You could just go ahead and download from the links mentioned above, but there’s another way - which might not require a download at all if you’ve already been working with Arduino or JeeNode boards.