The diagram of boot sequence

The premise of this sequence diagram is NuttX12.4.0, cxd56xx, non-SMP and Flat build.

The beginning of boot sequence is __start(). __start() will call nx_start(). nx_start() will initialize the kernel and call nsh_main(). nsh_main() will execute NuttShell(NSH). nx_start() is NuttX standard function, but the behavior depends on some kernel configurations. For example, the calling nsh_main() is also configurable. About related kernel configurations, see The list of related kernel configurations.