System Customization

This page covers four common system-customization paths: device tree, kernel configuration, Buildroot packages, and overlay file overrides. For a complete list of configuration options, see project/cfg-all-items-introduction.txt.

Board Configuration Files

reCamera Pro configuration is under:

project/cfg/BoardConfig_Recamera2/
├── BoardConfig-EMMC-RK801-RV1126B_V1-IPC.mk        # 32-bit
├── BoardConfig-EMMC-RK801-RV1126B_V1-IPC_64BIT.mk  # 64-bit (recommended)
├── RECAMERA2-IPC-RELEASE-NOTES.md
└── overlay/                                        # 15 overlay directories

After ./build.sh lunch, .BoardConfig.mk at the SDK root is a symbolic link to the selected file. Edit the actual configuration file; changes will be picked up through the symlink.

Key settings in the 64-bit configuration:

export RK_ARCH=arm64
export RK_CHIP=rv1126b
export RK_TOOLCHAIN_CROSS=aarch64-rockchip1240-linux-gnu
export RK_BOOT_MEDIUM=emmc
export RK_UBOOT_DEFCONFIG=rv1126b_recamera2_defconfig
export RK_UBOOT_DEFCONFIG_FRAGMENT="rk-emmc.config rv1126b-ipc.config"
export RK_UBOOT_RKBIN_MINIALL_INI_FILE=RV1126BMINIALL_IPC.ini
export RK_KERNEL_DEFCONFIG=rv1126b_ipc_defconfig
export RK_KERNEL_DEFCONFIG_FRAGMENT="rv1126b-display.config rv1126b-sdiowifi.config rv1126b-bt.config rv1126b-recamera2.config"
export RK_KERNEL_DTS=rv1126b-recamera2-v1.dts
export RK_KERNEL_RC_DTO=y
export RK_BUILDROOT_DEFCONFIG=recamera2_buildroot_aarch64_defconfig
export RK_APP_TYPE=RKIPC_RV1126B_RECAMERA2
export RK_PARTITION_CMD_IN_ENV="32K(env),512K@32K(idblock),4M@1M(uboot),64K(misc),10M(recovery),11M(boot),3G(rootfs),-(userdata),"
export RK_PARTITION_FS_TYPE_CFG=rootfs@IGNORE@ext4,userdata@/userdata@ext4
export RK_ENABLE_RECOVERY=y
export RK_MISC=recovery-misc.img
export RK_OTA_RESOURCE="boot.img rootfs.img"
export RK_OTA_VERSION=V1.0.10
export RK_BOOTARGS_CMA_SIZE="8M"
export RK_AIISP_MODEL=NONE
export RK_ENABLE_WIFI=y
export RK_ENABLE_WIFI_CHIP=AP6XXX
export RK_ENABLE_BLUETOOTH=y
export RK_APP_RECAMERA_WEB=y
export RK_APP_RECAMERA_NOTIFY=y
export RK_APP_RECAMERA_ONVIF=y
export RK_APP_RECAMERA_SERVICES=y
export RK_APP_RKLLM_INFERENCE=y
export RK_BUILD_APP_TO_OEM_PARTITION=n
export RK_FREETYPE_USE_BUILDROOT=y
export RK_CAMERA_SENSOR_IQFILES="ainr/sc450ai_default_default.json ainr/sc450ai ainr/sc850sl ainr/sc850sl_default_default.json"

After changing the board configuration, clean the affected components with ./build.sh clean before rebuilding to avoid mixing outputs from different configurations.

1. Device-Tree Customization

File Layout

Kernel DTS files are under sysdrv/source/kernel/arch/arm64/boot/dts/rockchip/:

File	Purpose
rv1126b-recamera2-v1.dts	Top-level entry point (selected by RK_KERNEL_DTS); model = "Rockchip RV1126B RECAMERA PRO Board"
rv1126b-recamera2-cam-csi0.dtsi	CSI0 camera path
rv1126b-recamera2-cam-csi1.dtsi	CSI1 camera path
rv1126b-recamera2-disp.dtsi	Display path
rv1126b-recamera2-ext-cam-csi1.dts	Expansion-board camera, compiled as .dtbo
rv1126b-recamera2-baseboard-0.dts / -baseboard-1.dts	Baseboard variants
rv1126b-recamera2-extboard-0.dts / -extboard-1.dts	Expansion-board variants

The commented-out includes in rv1126b-recamera2-v1.dts (rv1126b-aoa.dtsi, rv1126b-recamera2.dtsi, and rv1126b-recamera2-v1.dtsi) indicate that this DTS is self-contained: the power tree (vcc12v_dcin → vcc5v0_sys → vdd_npu, etc.) is defined directly in the top-level file using regulator-fixed.

Change the Kernel Command Line

The top-level chosen node is:

chosen {
    bootargs = "earlycon=uart8250,mmio32,0x20810000 console=ttyFIQ0 rw root=PARTUUID=614e0000-0000 rootfstype=ext4 rootwait snd_soc_core.prealloc_buffer_size_kbytes=16 coherent_pool=32K";
};

Do not change the CMA size here. Set RK_BOOTARGS_CMA_SIZE in the board configuration instead; build.sh adds it to a command-line fragment (__PREPARE_BOARD_CFG → RK_KERNEL_CMDLINE_FRAGMENT).

DTBO (Runtime Device-Tree Overlays)

With RK_KERNEL_RC_DTO=y and kernel CONFIG_OF_OVERLAY=y, reCamera Pro uses DTBOs to support one firmware image across multiple baseboards and expansion boards:

1. At build time, each rv1126b-recamera2-ext-*.dts is compiled into a corresponding .dtbo.
2. __PACKAGE_OEM() in build.sh copies sysdrv/source/objs_kernel/arch/arm64/boot/dts/rockchip/rv1126b-recamera2-ext-*.dtbo to /oem/usr/share/.
3. At boot, the S00board-id overlay reads the ADC to identify the board and writes the result to /run/board_id.env.
4. A startup script uses the detected ID to select a .dtbo to apply.

Board-identification mechanism (overlay-buildroot-board-id/etc/init.d/S00board-id):

ADC device       : /sys/bus/iio/devices/iio:device0
Output file      : /run/board_id.env
Samples          : Average of 3 readings
Tolerance        : 440
ADC levels       : 0 1365 2730 4094 5460 6824 8191
Corresponding V  : 0.0 0.3 0.6 0.9 1.2 1.5 1.8 V
Baseboard revs   : V0.9 V1.0 V1.1 V1.2 V1.3 V1.4 V1.5 (BASEBOARD_VERSIONS)
Baseboard models : TYPE0 ... TYPE6 (BASEBOARD_MODELS)
Expansion revs   : V0.9 ... V1.5 (EXPBOARD_VERSIONS)
Expansion models : TYPE0 ... TYPE6 (EXPBOARD_MODELS)

To add a hardware variant: add a resistor-divider level → update the LEVELS / VERSIONS / MODELS arrays in S00board-id → add the corresponding .dts → add a branch to the startup script. Keep all three parts in sync; otherwise, the new board may be identified as an existing model.

Change the Camera Sensor

1. Confirm that the matching driver is set to m or y in the kernel fragment (rv1126b-recamera2.config already includes many drivers, such as SC450AI, SC850SL, GC2053, and IMX415). Enable the appropriate CONFIG_VIDEO_xxx option if the driver is missing.
2. Update the camera node's compatible, I2C address, clock, and power regulators in the DTS.
3. Place the IQ file under media/isp/camera_engine_rkaiq/rkaiq/iqfiles/isp35/ and update RK_CAMERA_SENSOR_IQFILES in the board configuration.
4. Rebuild kernel + media + firmware.

2. Kernel Configuration

./build.sh kernelconfig      # Open menuconfig; savedefconfig runs on exit
./build.sh kernel            # Rebuild the kernel
./build.sh clean kernel      # Clean the kernel outputs

kernelconfig saves a defconfig.before snapshot first. On exit, it compares the configuration and writes defconfig only if there are actual changes, avoiding irrelevant diffs.

The configuration is composed of RK_KERNEL_DEFCONFIG=rv1126b_ipc_defconfig plus four fragments applied in order:

Fragment	Contents
rv1126b-display.config	Display settings
rv1126b-sdiowifi.config	SDIO Wi-Fi
rv1126b-bt.config	Bluetooth
rv1126b-recamera2.config	Seeed customizations; edit this file

rv1126b-recamera2.config is under sysdrv/source/kernel/arch/arm64/configs/ (the 32-bit version is the file with the same name under arch/arm/configs/; for the 64-bit board, edit the arm64 file). It ends with a #### recamera2 defconfig #### marker. Seeed's additions are after this marker, including:

CONFIG_CAN=y / CONFIG_CAN_RK3576=y            # CAN bus
CONFIG_STMMAC_ETHTOOL=y / CONFIG_DWMAC_ROCKCHIP_TOOL=y / CONFIG_REALTEK_PHY=y / CONFIG_MAXIO_PHY=y
CONFIG_GENERIC_ADC_BATTERY=y / CONFIG_CHARGER_GPIO=y / CONFIG_POWER_SUPPLY_DEBUG=y
CONFIG_SND_SOC_ES7202=y                        # Microphone-array ADC
CONFIG_TYPEC_AW35615=y / CONFIG_TYPEC_TCPM=y   # USB Type-C
CONFIG_NEW_LEDS=y / CONFIG_LEDS_CLASS=y / CONFIG_LEDS_PWM=y / CONFIG_LEDS_TRIGGERS=y
CONFIG_LEDS_TRIGGER_TIMER=y / _HEARTBEAT=y / _PATTERN=y
CONFIG_RTC_DRV_PCF8563=y                       # RTC
CONFIG_INV_ICM42670_I2C=y                     # IMU (used by recamera_utils/hw_test/imu_test.py)
CONFIG_FANOTIFY=y
CONFIG_CRYPTO*=m / CONFIG_CRYPTO_DEV_ROCKCHIP=m
CONFIG_OF_OVERLAY=y                            # DTBO support
CONFIG_DRM_PANEL_ILITEK_ILI9881C=y / CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2=y
CONFIG_INPUT_TOUCHSCREEN=y / CONFIG_TOUCHSCREEN_GOODIX=y
CONFIG_USB_CONFIGFS_NCM=y
CONFIG_NETFILTER=y / CONFIG_IP_NF_IPTABLES=y / CONFIG_IP_NF_FILTER=y / CONFIG_BPFILTER=y

The recommended way to add kernel options is to append them after the Recamera2 section in rv1126b-recamera2.config, rather than editing rv1126b_ipc_defconfig directly. The latter is an upstream Rockchip file and is more likely to conflict during SDK upgrades.

Notable existing choices:

• CONFIG_PANIC_ON_OOPS=y + CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y + CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y: oops, soft lockup, and hard lockup all cause a panic. Consider disabling these temporarily during development; otherwise, a fault immediately reboots the system and removes the live state needed for debugging.
• CONFIG_ROCKCHIP_DEBUG=y, CONFIG_DEBUG_FS=y, CONFIG_RK_CMA_PROCFS=y, CONFIG_RK_DMABUF_PROCFS=y, CONFIG_RK_MEMBLOCK_PROCFS=y, and CONFIG_ROCKCHIP_RGA_PROC_FS=y: debug nodes are enabled. Memory and RGA statistics under /proc/rk* and /sys/kernel/debug/ are useful for investigating memory leaks.
• CONFIG_ELF_CORE=y + CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS=y: enables coredumps. __BUILD_ENABLE_COREDUMP_SCRIPT() in build.sh can generate a script to enable them.
• CONFIG_VIDEO_RK_IRCUT is not enabled. Enable it yourself if you need IRCUT control.

3. Buildroot Customization

Location and Extraction

Buildroot sources are provided as an archive:

sysdrv/tools/board/buildroot/buildroot-2023.02.6.tar.gz
sysdrv/tools/board/buildroot/recamera2_buildroot_aarch64_defconfig   # 64-bit (this board)
sysdrv/tools/board/buildroot/recamera2_buildroot_defconfig           # 32-bit
sysdrv/tools/board/buildroot/busybox.config
sysdrv/tools/board/buildroot/{busybox_patch,mpv_patch,qemu_patch,hcitool_patch,prelink-cross_patch}
sysdrv/tools/board/buildroot/font

The first ./build.sh rootfs extracts it to sysdrv/source/buildroot/buildroot-2023.02.6/. Build outputs are under:

sysdrv/source/buildroot/buildroot-2023.02.6/output/
├── staging/    # Buildroot development sysroot (headers + libraries)
├── target/     # Target rootfs contents
├── host/       # Host-side tools
└── build/      # Package build directories

staging/ is for applications in the full BSP that link against Buildroot packages. For ordinary application development, use the recamera_pro_toolchain.

Common Commands

./build.sh buildrootconfig   # Open Buildroot menuconfig; savedefconfig runs on exit
./build.sh rootfs            # Rebuild rootfs
./build.sh clean rootfs      # Clean rootfs outputs

Add a Package

1. Select the package in ./build.sh buildrootconfig, then exit and save; the defconfig is updated automatically.
2. If the defconfig is not updated automatically (some packages are selected through dependencies), add BR2_PACKAGE_XXX=y manually to sysdrv/tools/board/buildroot/recamera2_buildroot_aarch64_defconfig.
3. Rebuild with ./build.sh rootfs.
4. Verify the package, for example with ls sysdrv/source/buildroot/buildroot-2023.02.6/output/target/usr/bin/.

To add a small BusyBox utility such as i2cdetect or nc, edit busybox.config. The board configuration already has options such as RK_ENABLE_SYSSTAT=y, RK_ENABLE_FIO=y, and RK_ENABLE_I2C_TOOLS=y, showing that common tools can be enabled through RK_ENABLE_* switches. Look for an existing switch before editing the defconfig directly.

About /oem

RK_BUILD_APP_TO_OEM_PARTITION=n, so /oem is a regular directory inside the rootfs, not a separate partition. During packaging, build.sh copies output/out/oem/ into the oem/ subdirectory of the rootfs staging area and then removes the separate OEM directory. Therefore:

• Files under oem/ in an overlay (for example, overlay-buildroot-go2rtc/oem/usr/bin/go2rtc) end up at /oem/usr/bin/go2rtc on the device.
• /oem is updated together with the rootfs. To change it, reflash rootfs.img; it cannot be flashed separately as an OEM partition.

4. Overlay File Overrides

Overlays are the main mechanism for Seeed's rootfs customizations and often the easiest path to get started.

How It Works

Implementation in build.sh (around line 2971):

for overlay_dir in $RK_POST_OVERLAY; do
    if [ -d "$tmp_path/overlay/$overlay_dir" ]; then
        rsync -a --ignore-times --keep-dirlinks --chmod=u=rwX,go=rX --exclude .empty \
            $tmp_path/overlay/$overlay_dir/* $RK_PROJECT_PACKAGE_ROOTFS_DIR/
    fi
done

In other words, files under project/cfg/BoardConfig_Recamera2/overlay/<name>/ are rsynced into the rootfs staging directory, preserving their relative paths.

cfg-all-items-introduction.txt describes RK_POST_OVERLAY as follows:

Overlay resource files are copied to the filesystem. For example, create overlay/user_overlay_files under the corresponding BoardConfig.mk directory and set RK_POST_OVERLAY=user_overlay_files.

Currently Enabled Overlays

RK_POST_OVERLAY lists 14 entries that map to 15 directories (go2rtc has three directories, but only two are enabled):

Overlay directory	Installed contents	Purpose
overlay-buildroot-banner	/etc/motd, /etc/profile.d/banner.sh	reCamera ASCII logo; printed only in interactive non-SSH sessions
overlay-buildroot-hwclock	/etc/init.d/S20hwclock	Sync RTC and system time
overlay-buildroot-sshd	/etc/ssh/sshd_config, /etc/pam.d/sshd, /etc/init.d/S50sshd, /usr/libexec/ssh-login-lock.py	SSH service and failed-login lockout (5 attempts / 300 seconds)
overlay-buildroot-syslog-ng	/etc/syslog-ng.conf	Route logs to files and UDP
overlay-buildroot-vsftpd	/etc/vsftpd.conf, /etc/pam.d/vsftpd, /etc/shells, /etc/vsftpd.{chroot_,user_}list, /etc/init.d/S70vsftpd	FTP; hides the config directory
overlay-buildroot-log	/oem/usr/bin/websocket_log.py, /oem/usr/etc/init.d/S10log	UDP 5140 → WebSocket 8765
overlay-buildroot-ttyd	/oem/usr/etc/init.d/S50ttyd, /oem/usr/bin/ssh-login-whitelist.sh	Browser terminal (7681), allowlist root / admin
overlay-buildroot-udhcpc	/usr/share/udhcpc/default.script	DHCP script; eth0 DNS takes priority
overlay-buildroot-go2rtc	/oem/usr/etc/go2rtc/go2rtc.yaml, /oem/usr/etc/init.d/S50go2rtc	Stream configuration and startup script
overlay-buildroot-go2rtc-arm64	/oem/usr/bin/go2rtc	64-bit go2rtc binary
overlay-buildroot-board-id	/etc/init.d/S00board-id	Read board ID from ADC → /run/board_id.env
overlay-buildroot-asound	/etc/asound.conf	Six-channel capture → virtual devices for two microphones + two reference channels
overlay-buildroot-watchdog	/etc/init.d/S15watchdog	Hardware watchdog (-T 30 -t 15)
overlay-buildroot-rkenv	/etc/profile.d/RkEnv.sh	OEM_HOME, PATH, LD_LIBRARY_PATH, HOME=/userdata

Present but not enabled: overlay-buildroot-go2rtc-arm (32-bit go2rtc binary); the 64-bit board does not use it.

Add Your Own Overlay

# 1. Create a directory and arrange files by their target absolute paths
mkdir -p project/cfg/BoardConfig_Recamera2/overlay/my_overlay/etc/init.d
cp my_script.sh project/cfg/BoardConfig_Recamera2/overlay/my_overlay/etc/init.d/S60myservice

# 2. Append it to RK_POST_OVERLAY in the board configuration (keep the line-continuation backslash)
#    export RK_POST_OVERLAY="... overlay-buildroot-rkenv \
#    my_overlay"

# 3. Rebuild rootfs and package the firmware
./build.sh rootfs && ./build.sh firmware

Three Overlay Pitfalls

• rsync rewrites permissions: --chmod=u=rwX,go=rX means group and other users never get write permission. Uppercase X preserves execute permission only for directories or files that were already executable. Make scripts executable in the source overlay before building.
• .empty files are excluded: placeholder files used to create empty directories do not enter the image. This is intentional and preserves the directory structure.
• Overlays overwrite but do not delete: rsync is not passed --delete, so removing a file from an overlay does not remove it from the rootfs. To remove a file, use a Buildroot rootfs post-build script or RK_POST_CLEAN_FILES (__RUN_POST_CLEAN_FILES in build.sh).

5. U-Boot Customization

./build.sh uboot
./build.sh clean uboot

Configuration: RK_UBOOT_DEFCONFIG=rv1126b_recamera2_defconfig under sysdrv/source/uboot/u-boot/configs/, plus the rk-emmc.config and rv1126b-ipc.config fragments.

A key setting is CONFIG_BAUDRATE=1500000. Change boot delay, default boot target, fastboot support, and related options in this defconfig.

DDR initialization firmware is selected by RK_UBOOT_RKBIN_MINIALL_INI_FILE=RV1126BMINIALL_IPC.ini; outputs include idblock.img / download.bin. Changing DDR parameters is high risk; avoid it unless necessary.

build.sh contains __modify_file() and __modify_file_ddr_bin(), which modify rkbin DDR firmware parameters from the board configuration during U-Boot builds. Check these functions first when investigating DDR issues.

6. Partition-Table Customization

Edit RK_PARTITION_CMD_IN_ENV. Entries use size(name) or size@offset(name); - means use all remaining space:

32K(env),512K@32K(idblock),4M@1M(uboot),64K(misc),10M(recovery),11M(boot),3G(rootfs),-(userdata),

Also update RK_PARTITION_FS_TYPE_CFG, whose format is partition@mount-point@filesystem; IGNORE means that the partition is not mounted by fstab:

rootfs@IGNORE@ext4,userdata@/userdata@ext4

After changing these values, run:

./build.sh env          # Regenerate env.img
./build.sh firmware     # Repackage the firmware

Rewrite the partition table when flashing: run sudo ./rkflash.sh all, or at least upgrade_tool di -p output/image/parameter.txt. Flashing only rootfs without updating the partition table can misalign the partitions.

parse_partition_env(), parse_partition_file(), get_partition_dev_node(), and get_partition_num() in build.sh handle parsing; inspect these functions when debugging partition issues.

Important considerations:

• boot is only 11 M. Packaging fails if the kernel + DTB exceeds this size. After enabling many kernel features, check with ls -lh output/image/boot.img.
• rootfs is fixed at 3 G; userdata uses the remaining space. Increasing rootfs reduces userdata capacity.
• The kernel command line uses root=PARTUUID=614e0000-0000. Changing the partition order may affect the PARTUUID; after any partition change, verify that the DTS bootargs remain correct.

7. MCU Side (RT-Thread)

sysdrv/source/mcu/ contains RT-Thread firmware for the MCU built into RV1126B. It is independent of Linux:

sysdrv/source/mcu/
├── build.sh
├── docs/          # Rockchip_RV1126B_Quick_Start_RT-Thread_MCU_CN.pdf
├── prebuilts/
├── project/
├── readme.txt
└── rt-thread/

Build it with:

./build.sh mcu              # From the SDK root
# Or enter sysdrv/source/mcu/ and use its own build.sh

The mcu argument is handled separately before normal argument parsing in build.sh (if [ "$1" = "mcu" ]; then shift; build_mcu $@; fi). MCU builds may also be triggered automatically during U-Boot / kernel builds according to the configuration via build_mcu amp or build_mcu $RK_UBOOT_RKBIN_MCU_CFG.

The current board configuration does not explicitly enable the MCU. Check ./build.sh info to see whether it is included in the build.

Post-Customization Verification

./build.sh info                      # Confirm that the configuration took effect
./build.sh kernel && ./build.sh rootfs && ./build.sh firmware
ls -lh output/image/                 # Check that image sizes are reasonable (boot < 11M, rootfs < 3G)
sudo ./rkflash.sh all                # A partition-table change requires flashing everything

On the device:

# /bin/sdkinfo                       # Print Build Time / SDK Version / BoardConfig name
# cat /etc/ota_version               # Should be V1.0.10 (or your updated value)
# cat /proc/cmdline                  # Check that the command line matches expectations
# cat /run/board_id.env              # Check the detected board ID
# ls /oem/usr/share/*.dtbo           # Confirm the DTBO files are present
# zcat /proc/config.gz | grep XXX    # Check a kernel option (if IKCFG is enabled)

/bin/sdkinfo is generated by build.sh during packaging. It reports the SDK version and BoardConfig filename, making it the quickest way to identify which firmware build is running on the device.

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