1. (SIMPLE) If there is a combined bootloader and app binary provided, then you can use this and only need to flash one file.
   1. app_with_bootloader_vX.X.X_YYYYMMDD.hex with the version number and date.
2. (ALTERNATIVE) 3 files: bootloader.hex , app.hex and app_dfu.bin are provided
   1. bootloader.hex = bootloader binary
   2. app.hex and app_dfu.bin = application binaries (in hex and bin file format, used for flashing and upgrades over serial respectively).