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rtt-ctrl — Control RT-Smart from Linux

rtt-ctrl is a utility for remotely executing msh shell commands on RT-Smart (bigcore) from Linux (littlecore). It sends commands to the rc_server inside the RT-Smart kernel via IPCM (Inter-Processor Communication) and receives the execution results.

How It Works

Architecture

Linux (littlecore)                    RT-Smart (bigcore)
┌──────────────┐                     ┌──────────────┐
│ rtt-ctrl     │  IPCM port 7       │ rc_server    │
│ (user app)   │ ──────────────────→ │ (kernel)     │
│              │ ←────────────────── │              │
└──────┬───────┘   /dev/ipcm_user   └──────┬───────┘
       │                                    │
       │                              msh_exec(cmd)
       │                                    │
  response (ret code)              RT-Smart msh shell

Communication Flow

  1. Linux side: rtt-ctrl command opens /dev/ipcm_user
  2. Connects to RT-Smart's rc_server via IPCM port 7
  3. Sends command string as RC_CMD_EXEC message (max 128 bytes)
  4. RT-Smart side: rc_server executes the command via msh_exec()
  5. Returns the result (return code) as a response

Enabling

./build_sdk.sh enables RT_USING_RTT_CTRL by default.

# Default (rtt-ctrl enabled)
./build_sdk.sh

# To disable rtt-ctrl
./build_sdk.sh --no-rtt-ctrl

Internally, this adds #define RT_USING_RTT_CTRL to the defconfig source (configs/common_rttlinux.config). During build, menuconfig_to_code.sh copies this file to rtconfig.h, so editing rtconfig.h directly will be overwritten. When undefined, a weak symbol stub is used and "no rtt ctrl device library!" is displayed.

Source Code

File (SDK path) Role
src/common/cdk/kernel/ipcm/class/rtt-ctrl/rc_command.h Command protocol definitions (RC_CMD_EXEC, etc.)
src/common/cdk/kernel/ipcm/class/rtt-ctrl/rc_common.h Common header
src/common/cdk/kernel/ipcm/class/rtt-ctrl/rt-smart/rc_server.c RT-Smart side server implementation
src/common/cdk/kernel/ipcm/class/rtt-ctrl/linux/rc_client.c Linux side client implementation
src/common/cdk/kernel/ipcm/class/rtt-ctrl/server_ipc.c RT-Smart side IPC handling
src/common/cdk/kernel/ipcm/class/rtt-ctrl/client_ipc.c Linux side IPC handling
src/big/rt-smart/kernel/bsp/maix3/board/ipcm/rtt_ctrl_init.c RT-Smart kernel initialization

Usage

Basic

rtt-ctrl "command"

Examples

# List RT-Smart threads
rtt-ctrl "list_thread"

# Show memory usage
rtt-ctrl "free"

# List available msh commands
rtt-ctrl "help"

Notes

  • Command string must be 128 bytes or less
  • Connection timeout: approx. 1 second
  • Command response timeout: approx. 1 second
  • IPCM driver must be loaded (/dev/ipcm_user must exist)

Updating Only the RT-Smart Image

If you have already completed a full build with build_sdk.sh and want to toggle RT_USING_RTT_CTRL, you can edit rtconfig.h directly and do a partial build.

Note

During a full build, menuconfig_to_code.sh copies common_rttlinux.config → rtconfig.h, so direct edits are overwritten. Partial builds (make rt-smart-kernel, etc.) do not trigger this copy, so direct edits to rtconfig.h are preserved.

Partial Build

Run these inside the Docker container in the k230_sdk/ directory.

# Edit rtconfig.h to add/remove RT_USING_RTT_CTRL
vi src/big/rt-smart/kernel/bsp/maix3/rtconfig.h

# 1. RT-Smart kernel rebuild — picks up rtconfig.h changes
make rt-smart-kernel

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

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

Since this change does not affect init.sh or user applications, mpp and rt-smart-apps builds are not needed.

Writing to SD Card

Instead of re-flashing the full image, you can update only the RT-Smart partition. The SD card GPT partition layout is as follows:

Partition Offset Size Contents
rtt 10 MB 20 MB RT-Smart (big-core) firmware
linux 30 MB 50 MB Linux (little-core) firmware
rootfs 128 MB variable ext4 root filesystem
fat32appfs after rootfs remainder FAT32 application storage

After building, write rtt_system.bin to the rtt partition on the SD card using dd:

# Replace /dev/sdX with your SD card device (e.g., /dev/sdb)
sudo dd if=output/k230_canmv_defconfig/images/big-core/rtt_system.bin \
    of=/dev/sdX bs=1M seek=10 conv=notrunc status=progress

Warning

Replace /dev/sdX with the correct SD card device for your environment. Specifying the wrong device will destroy data.

File Role
./build_sdk.sh RT_USING_RTT_CTRL enablement logic
k230_sdk/src/big/rt-smart/kernel/bsp/maix3/configs/common_rttlinux.config Defconfig source (copied to rtconfig.h during build)
k230_sdk/src/big/rt-smart/kernel/bsp/maix3/rtconfig.h RT-Smart kernel configuration (auto-generated)