Px4esc-v1_default bootloader bin file

I’m trying to port px4 to stm32f446re board, and starting it at px4esc-v1_default since it uses same board.

There are two target regarding this; px4esc-v1_bootloader, px4esc-v1_default.

When I build px4esc-v1_bootloader, just firmware_nuttx image file generated, but firmware_nuttx.bin file doesn’t appear.

Can I use this image file instead of *.bin file?
(I just have tried to write image file, but it doesn’t respond when I executing make px4esc-v1_default upload command)