To build the bootloader, you will need the PX4 development toolchain, which you should have setup in your development virtual machine. When the toolchain has been installed, you can run the following commands in the command line tool available on your operating system or installed through the development toolchain.
First, clone the PX4 bootloader repository: git clone https://github.com/PX4/Bootloader
Then, change your working directory to the just cloned repository: cd Bootloader/
Update the submodules:git submodule update --recursive --init
Build the RDDRONE-FMUK66 PX4 bootloader: make fmuk66v3_bl
The bootloader is now available under Bootloader/build/fmuk66v3_bl/fmuk66v3_bl.bin
Updating your local clone of the PX4 Bootloader repository
In case you already have the bootloader repository cloned, you can pull in the most recent changes and rebuild the bootloader binary. Open a console and go to your local clone of the PX4 Bootloader repository
If you want to checkout another branch, or switch back to master branch, you can do that first.
Fetch available branches in the remote (online) repository: git fetch
Checkout another branch: git checkout branchname
Now make sure your local repository is up-to-date with the latest upstream changes: