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USB

Luckfox Lume provides one USB 2.0 Type-A Host port and one USB 2.0 Type-C Device port. The Type-A port connects peripherals such as USB flash drives and UVC cameras. The Type-C port provides 5V power input and USB device functionality.

This chapter explains how to mount a USB flash drive and capture photos and video with the IMX415 8MP USB Camera (A).

1. Mounting a USB Flash Drive​

1.1 Identifying the USB Flash Drive​

Insert the USB flash drive into the Type-A Host port, then check the block devices, filesystem, and kernel log:

root@luckfox:~# lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
sda           8:0    1  14.6G  0 disk 
`-sda1        8:1    1  14.6G  0 part

root@luckfox:~# blkid /dev/sda1
/dev/sda1: UUID="266D-2C14" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="97917c8f-01"

root@luckfox:~# dmesg | tail -n 30
[ 5208.308091] usb 1-1: USB disconnect, device number 2
[ 5210.481916] usb 1-1: new high-speed USB device number 3 using sunxi-ehci
[ 5210.683053] usb 1-1: New USB device found, idVendor=14cd, idProduct=1212, bcdDevice= 1.00
[ 5210.692222] usb 1-1: New USB device strings: Mfr=1, Product=3, SerialNumber=2
[ 5210.700191] usb 1-1: Product: Mass Storage Device
[ 5210.705494] usb 1-1: Manufacturer: Generic
[ 5210.710070] usb 1-1: SerialNumber: 121220160204
[ 5210.716338] usb-storage 1-1:1.0: USB Mass Storage device detected
  • /dev/sda: The entire USB flash drive, with a capacity of approximately 14.6 GiB.
  • /dev/sda1: A partition identified as FAT32; no formatting is needed.
  • high-speed: A USB 2.0 high-speed connection.
  • Empty MOUNTPOINTS: The partition is not mounted.

1.2 Mounting and Verification​

Create a mount point and mount the drive read-only to avoid modifying existing files:

root@luckfox:~# mkdir -p /mnt/usb

root@luckfox:~# mount -t vfat -o ro /dev/sda1 /mnt/usb

root@luckfox:~# df -h /mnt/usb
Filesystem                Size      Used Available Use% Mounted on
/dev/sda1                14.6G     96.0K     14.6G   0% /mnt/usb

The output shows that /dev/sda1 has been successfully mounted at /mnt/usb.

1.3 Unmounting the USB Flash Drive​

When finished, leave the USB drive directory and close any programs accessing the drive. Then synchronize data and unmount it:

cd /root
sync
umount /mnt/usb
lsblk -o NAME,SIZE,TYPE,FSTYPE,MOUNTPOINTS

Remove the USB flash drive after MOUNTPOINTS for sda1 becomes empty again.

2. USB Camera​

2.1 Installing v4l2-ctl​

v4l2-ctl is part of v4l-utils. Cross-compile it using the cached v4l-utils 1.22.1 source archive and the 32-bit ARM toolchain included in the Luckfox Lume SDK.

  1. Locate the source and toolchain:

    cd <Luckfox_Lume_SDK>/

    ls -lh buildroot/buildroot-202205/dl/libv4l/v4l-utils-1.22.1.tar.bz2
    ls -l out/toolchain/gcc-linaro-11.3.1-2022.06-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-gcc

    Relevant files:

    ItemLocation
    Source archivebuildroot/buildroot-202205/dl/libv4l/v4l-utils-1.22.1.tar.bz2
    Toolchain directoryout/toolchain/gcc-linaro-11.3.1-2022.06-x86_64_arm-linux-gnueabihf/bin
    Compiler prefixarm-linux-gnueabihf-
    Target systemARMv7, 32-bit hard-float, Buildroot

  2. Build v4l2-ctl:

    cp <Luckfox_Lume_SDK>/buildroot/buildroot-202205/dl/libv4l/v4l-utils-1.22.1.tar.bz2 /tmp/

    tar -xjf /tmp/v4l-utils-1.22.1.tar.bz2

    cd /tmp/v4l-utils-1.22.1/

    ./configure \
       --host=arm-linux-gnueabihf \
       --disable-shared \
       --disable-nls \
       --disable-libdvbv5 \
       --disable-v4l2-ctl-libv4l \
       --disable-qv4l2 \
       --disable-qvidcap \
       --disable-bpf \
       --without-jpeg \
       LDFLAGS="-static-libstdc++ -static-libgcc"

    make -C utils/v4l2-ctl -j4
    arm-linux-gnueabihf-strip utils/v4l2-ctl/v4l2-ctl

  3. Transfer it to the board:

    scp /tmp/v4l-utils-1.22.1/utils/v4l2-ctl root@192.168.9.74:/tmp/v4l2-ctl

    Add execute permission on the board and check the version:

    root@luckfox:~# chmod +x /tmp/v4l2-ctl
    root@luckfox:~# /tmp/v4l2-ctl --version
    v4l2-ctl 1.22.1

2.2 Installing FFmpeg​

  1. Download the FFmpeg source:

    cd /tmp
    wget https://ffmpeg.org/releases/ffmpeg-6.1.6.tar.xz
    tar -xf ffmpeg-6.1.6.tar.xz
    cd ffmpeg-6.1.6

  2. Configure a minimal build using the Lume 32-bit ARM toolchain:

    export CROSS=<Luckfox_Lume_SDK>/out/toolchain/gcc-linaro-11.3.1-2022.06-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-

    ./configure \
       --enable-cross-compile \
       --arch=arm \
       --cpu=cortex-a7 \
       --target-os=linux \
       --cross-prefix="$CROSS" \
       --disable-everything \
       --disable-autodetect \
       --disable-doc \
       --disable-debug \
       --disable-network \
       --enable-small \
       --enable-ffmpeg \
       --enable-ffprobe \
       --enable-indev=v4l2 \
       --enable-protocol=file \
       --enable-demuxer=mjpeg,avi,mov \
       --enable-muxer=mjpeg,avi,image2,mov \
       --enable-parser=mjpeg \
       --enable-decoder=mjpeg \
       --enable-encoder=mjpeg \
       --enable-filter=scale,format,null \
       --enable-swscale \
       --enable-avfilter

  3. Build:

    make -j$(nproc)
    "${CROSS}strip" ffmpeg ffprobe
    file ffmpeg ffprobe
    ls -lh ffmpeg ffprobe

  4. Copy the binaries to the board:

    scp ffmpeg ffprobe root@<IP>:/root/

  5. Run on the board:

    chmod +x /root/ffmpeg /root/ffprobe
    /root/ffmpeg -version
    /root/ffmpeg -hide_banner -devices

2.3 Taking Photos​

  1. List the camera devices:

    root@luckfox:~# ls /dev/video*
    /dev/video0  /dev/video1
    root@luckfox:~# v4l2-ctl --list-devices
    Allwinner Vin (platform:sunxi-vin-media):
          /dev/media1

    USB Camera: USB Camera (usb-sunxi-ehci-1):
          /dev/video0
          /dev/video1
          /dev/media0

    Check the purpose of each node, pixel formats, resolutions, and frame rates:

    v4l2-ctl -d /dev/video0 --info
    v4l2-ctl -d /dev/video1 --info
    v4l2-ctl -d /dev/video0 --list-formats-ext

    /dev/video0 lists Video Capture among its capabilities and is used for image capture. /dev/video1 provides Metadata Capture and cannot be used in place of the image capture node.

  2. Take a photo with the USB camera and save it with the specified filename:

    v4l2-ctl -d /dev/video0 \
        --set-fmt-video=width=1920,height=1080,pixelformat=MJPG \
        --set-parm=30 \
        --stream-mmap=2 --stream-skip=10 --stream-count=1 \
        --stream-to="usb-camera.jpg"

    The command displays Frame rate set to 30.000 fps and capture progress. When complete, it produces a 1920×1080 JPEG file.

    • --set-fmt-video: Select the 1920×1080 resolution and MJPG format.
    • --stream-mmap=2: Use two memory-mapped buffers.
    • --stream-skip=10: Skip the first 10 frames, then save one frame.
    • --stream-to: Save the camera output. A single MJPG frame can be saved directly as JPEG without additional encoding.

2.4 Recording Video​

  1. Confirm that the camera's image capture node is /dev/video0 and that the MOV muxer is enabled in FFmpeg:

    /root/ffmpeg -hide_banner -muxers | grep ' mov '

  2. Record a 10-second video at 640×480 and 30 fps using the camera's MJPEG output, and save it directly as an MP4 file:

    /root/ffmpeg -n -f v4l2 \
       -input_format mjpeg \
       -video_size 640x480 \
       -framerate 30 \
       -i /dev/video0 \
       -t 10 \
       -an \
       -c:v copy \
       -f mov \
       /root/output.mp4
    • -f v4l2: Capture video from a Linux V4L2 camera.
    • -input_format mjpeg: Use the camera's MJPEG-compressed stream to reduce memory and CPU usage.
    • -video_size 640x480, -framerate 30: Request capture at 640×480 and 30 fps.
    • -t 10: Record for 10 seconds. To stop early, press Ctrl+C and wait for FFmpeg to finish writing the file trailer.
    • -an: Do not capture audio.
    • -c:v copy: Write the MJPEG video stream directly into the container without re-encoding.
    • -f mov: Explicitly select the MOV/MP4 muxer. This minimal build enables only the mov muxer, so the .mp4 extension alone cannot select it automatically. This option is required.
    • -n: Stop if the destination file already exists to avoid overwriting it. Use -y instead if overwriting is intended.

  3. Output:

  4. If FFmpeg immediately displays Killed after starting, check for an out-of-memory condition:

    dmesg | grep -Ei 'out of memory|oom-killer|killed process' | tail -n 20
    grep -E 'MemFree|MemAvailable|SwapTotal' /proc/meminfo
    du -ak /tmp | sort -n | tail -n 20