RT-Smart Boot Customization¶

This guide explains the RT-Smart (bigcore) boot sequence and how to create an image that waits at the msh shell prompt.

RT-Smart Boot Sequence¶

The K230 bigcore (RT-Smart) boots in the following order:

RT-Smart kernel startup
  ↓
Component initialization (INIT_BOARD_EXPORT → ... → INIT_APP_EXPORT)
  ├── finsh_system_init() → creates and starts msh shell thread "tshell"
  └── ...
  ↓
Mount ROMFS at /
  ↓
main() runs → msh_exec("/bin/init.sh")
  ↓
Application launches according to init.sh contents

msh Shell Thread¶

The msh shell thread (tshell) is automatically started during component initialization (finsh_system_init). If main() does not launch a blocking application, the msh shell becomes interactively usable via the serial console.

main() Behavior¶

main() executes RT_SHELL_PATH (default: /bin/init.sh) via msh_exec().

// k230_sdk/src/big/rt-smart/kernel/bsp/maix3/applications/main.c
#ifndef RT_SHELL_PATH
#define RT_SHELL_PATH "/bin/init.sh"
#endif

int main(void)
{
    // ...
    msh_exec(RT_SHELL_PATH, strlen(RT_SHELL_PATH)+1);
    return 0;
}

Default Behavior¶

The default init.sh launches the face detection demo application (fastboot_app.elf).

# k230_sdk/src/big/rt-smart/init.sh (default)
/bin/fastboot_app.elf /bin/test.kmodel

fastboot_app.elf starts camera, video output, and face detection, running as a blocking process. While the msh shell still accepts input, the console output is dominated by the application.

init.sh Copy Path¶

init.sh is embedded into the firmware image through the following path:

k230_sdk/src/big/rt-smart/init.sh
  ↓ (copied by make mpp)
k230_sdk/src/big/rt-smart/userapps/root/bin/init.sh
  ↓ (converted to ROMFS by mkromfs.py)
k230_sdk/src/big/rt-smart/kernel/bsp/maix3/applications/romfs.c
  ↓ (built into kernel)
RT-Smart kernel binary

Creating an msh Shell-Wait Image¶

Method 1: Using the Build Script (Default)¶

./build_sdk.sh generates an image that does not launch fastboot_app.elf and instead waits at the msh shell prompt by default.

./build_sdk.sh

To generate an image that launches fastboot_app.elf, pass --with-fastboot.

./build_sdk.sh --with-fastboot

Method 2: Manually Editing init.sh¶

Edit init.sh directly and replace the fastboot_app.elf launch line with a comment or leave it empty.

# k230_sdk/src/big/rt-smart/init.sh
# msh shell ready

Then rebuild the SDK.

Partial Build¶

After modifying init.sh, you can run a full build (make), but the following partial build steps save time. Run these inside the Docker container in the k230_sdk/ directory.

# 1. MPP build — copies init.sh to userapps/root/bin/
make mpp

# 2. RT-Smart user apps + ROMFS regeneration — mkromfs.py → romfs.c
make rt-smart-apps

# 3. RT-Smart kernel rebuild — picks up updated romfs.c
make rt-smart-kernel

# 4. OpenSBI rebuild — embeds RT-Smart binary as payload
make big-core-opensbi

# 5. Final SD card image generation
make build-image

A full build (make) includes all of the above plus Linux (littlecore) and more, so partial builds are faster when only init.sh has changed.

File	Role
`k230_sdk/src/big/rt-smart/init.sh`	Boot script source
`k230_sdk/src/big/rt-smart/kernel/bsp/maix3/applications/main.c`	RT-Smart main(). Calls `msh_exec(RT_SHELL_PATH)`
`k230_sdk/src/big/rt-smart/kernel/bsp/maix3/applications/romfs.c`	Auto-generated. Created by mkromfs.py from `userapps/root/`
`k230_sdk/src/big/rt-smart/kernel/bsp/maix3/rtconfig.h`	RT-Smart kernel config (`RT_USING_MSH`, etc.)
`k230_sdk/src/big/rt-smart/kernel/rt-thread/components/finsh/shell.c`	msh shell thread implementation
`k230_sdk/Makefile`	Build pipeline (`mpp` → `rt-smart-apps` → `rt-smart-kernel`)