YUV Sensor (MediaTek Imgsensor)

Note

All command operations presented in this chapter are based on the IoT Yocto v23.1, Genio 1200-EVK and Onsemi AP1302 ISP and AR0830 sensor. You might get different operation results depending on the platform you use.

Camera Daughter Board

The YUV camera DTB for Genio 1200-EVK is CAM DTB-D6. It contains an Onsemi AP1302 ISP and an AR0830 Sensor.

../../../../_images/sw_yocto_app-dev_camera_cam-dtb-d6.jpeg

Camera DTB D6 - Onsemi AP1302 ISP and AR0830 Sensor

Connect The Camera To The EVK

There are 3 MIPI-CSI sockets on Genio 1200-EVK, which are CSI0, CSI1, and CSI2. In the following figure, the camera DTB is connected to the CSI0 socket.

../../../../_images/sw_yocto_app-dev_camera_g1200_connect-d6.png

Connect Camera DTB D6 to Genio 1200-EVK

The hardware connection is AR0830 ---> AP1302 ---> MIPI-CSI On EVK. The camera daughter board can be configured in ISP mode and Bypass mode. In ISP mode, the images from the AR0830 camera module are passed to AP1302 ISP before being received by the EVK. In Bypass mode, the images from the AR0830 camera module are transferred to the EVK directly. By default, IoT Yocto only supports ISP mode.

To configure the camera DTB D6 to ISP mode, you MUST set 6 jumpers and 1 camera sensor as shown in the figure below. The jumpers MUST be correctly set and the camera sensor MUST be connected to the CAMERA 0 slot.

../../../../_images/sw_yocto_app-dev_camera_cam-dtb-d6-isp-mode.png

Camera DTB D6 - ISP mode

Warning

Please make sure all the above settings, including the jumpers, camera slot, and MIPI-CSI socket, are correct. Otherwise, the I2C connection between the sensor, ISP, and SoC will fail.

Select Camera Device Tree Blob Overlay

The camera device is inactive by default, so the kernel has to load a specific device tree blob overlay to enable it. Please refer to the bl33 (u-boot) section for more details.

YUV Camera DTBO for Genio 1200-EVK

Platform

CSI0

CSI1

CSI2

DTBO

Usage

Genio 1200-EVK

AP1302+ AR0830

x

x

camera-ar0830-ap1302-csi0.dtbo

Enable 4-lane CAM-DTB-D6 w/ Onsemi AR0830 on CSI0

Genio 1200-EVK

AP1302+ AR0830 (2 lane)

x

x

camera-ar0830-ap1302-2lanes-csi0.dtbo

Enable 2-lane CAM-DTB-D6 w/ Onsemi AR0830 on CSI0

Genio 1200-EVK

x

AP1302+ AR0830

x

camera-ar0830-ap1302-csi1.dtbo

Enable 4-lane CAM-DTB-D6 w/ Onsemi AR0830 on CSI1

Genio 1200-EVK

x

x

AP1302+ AR0830

camera-ar0830-ap1302-csi2.dtbo

Enable 4-lane CAM-DTB-D6 w/ Onsemi AR0830 on CSI2

 
genio-flash --list-dtbo
List of available DTBO:
        - camera-ar0830-ap1302-2lanes-csi0.dtbo
        - camera-ar0830-ap1302-csi0.dtbo
        - camera-ar0830-ap1302-csi1.dtbo
        - camera-ar0830-ap1302-csi2.dtbo
        - ...
genio-flash --load-dtbo camera-ar0830-ap1302-csi0.dtbo --load-dtbo gpu-mali.dtbo --load-dtbo apusys.dtbo --load-dtbo video.dtbo

Warning

Please select the DTBO according to the CSI slot to which the camera sensor is connected. For example, if the camera is connected to the CSI0 slot, please load the dtbo camera-ar0830-ap1302-csi0.dtbo. Otherwise, the camera initialization will fail.

Supported Formats And Sizes

Platform

Sensor

Stream Type

Size

Frame rate

Format

MIPI Lanes

Genio 1200-EVK

Onsemi AP1302 & AR0830

Preview

1920x1080

30

UYVY

4

Genio 1200-EVK

Onsemi AP1302 & AR0830

Preview

2560x1440

30

UYVY

4

Genio 1200-EVK

Onsemi AP1302 & AR0830

Preview

3840x2160

24

UYVY

4

Genio 1200-EVK

Onsemi AP1302 & AR0830

Preview

1920x1080

30

UYVY

2

Genio 1200-EVK

Onsemi AP1302 & AR0830

Preview

2560x1440

30

UYVY

2

Genio 1200-EVK

Onsemi AP1302 & AR0830

Preview

3840x2160

12

UYVY

2

Note

The supported format, resolution, and frame rate are related to the capability of the sensor and SoC.

V4L2 Device Node

Camera ISP is a complicated feature that has a large number of device nodes. The camera ISP driver creates 123 video devices in total.

  • MTK-ISP-DIP-V4L2 has 68 devices

  • mtk-cam has 54 devices

  • mtk-v4l2-camera has 1 device

MTK-ISP-DIP-V4L2 and mtk-cam are used by the camera ISP middleware. The user can just focus on mtk-v4l2-camera which is for streaming.

v4l2-ctl --list-devices
...
mtk-cam (platform:16000000.camisp):
        (54 video devices)
        /dev/media2

mtk-v4l2-camera (platform:mtkcam0):
        /dev/video74

Launch Camera

The V4L2 nodes with the name mtk-v4l2-camera can be used for streaming. For the YUV sensor, there’s only 1 V4L2 device which is for the preview stream. The user can find the devices by the following command:

v4l2-ctl --list-device
mtk-v4l2-camera (platform:mtkcam0):
        /dev/video74
cat /sys/class/video4linux/video74/name
mtk-v4l2-camera@0-Preview

Important

The above v4l2 device node number is for example. The node number may change every time the system boots.

To quickly fetch the correct node and assign the environment variable:

declare -a VIDEO_DEV=(`v4l2-ctl --list-devices | grep mtk-v4l2-camera -A 1 | grep video | tr -d "\n"`)
printf "Preview Node\t= ${VIDEO_DEV[0]}\n"
Preview Node    = /dev/video74

Section Supported formats and Sizes shows the supported formats and sizes. The user can also use the v4l2 utility, v4l2-ctl, to list formats.

v4l2-ctl -d ${VIDEO_DEV[0]} --list-formats-ext
ioctl: VIDIOC_ENUM_FMT
        Type: Video Capture Multiplanar

        [0]: 'UYVY' (UYVY 4:2:2)
                Size: Discrete 1920x1080
                        Interval: Discrete 0.033s (30.000 fps)
        ...

To launch the camera, the user can use v4l2-ctl, gst-launch-1.0, or other V4L2 applications.

  • Use v4l2-ctl

    v4l2-ctl -d ${VIDEO_DEV[0]} --set-fmt-video=width=1920,height=1080,pixelformat=UYVY --stream-mmap --stream-count=10 --stream-to=/tmp/ap1302.yuv --verbose

  • Use gst-launch-1.0

    gst-launch-1.0 v4l2src device=${VIDEO_DEV[0]} ! video/x-raw,width=1920,height=1080,format=UYVY ! v4l2convert output-io-mode=dmabuf-import ! video/x-raw,width=1280,height=720 ! waylandsink sync=false
    ../../../../_images/sw_yocto_app-dev_camera_yuv-show-on-weston.png

    Show Preview stream on Weston

Note

To use MediaTek video codec and MDP hardware, the user has to load video.dtbo. For more details, please refer to Genio 1200-EVK Video Codec.

Sensor Launch Time

In our camera operation sequence, we follow the steps below:

  • Open Camera

    1. Power on the sensor

    2. Release the reset pin

    3. Configure the sensor settings

    4. Stream on the sensor

  • Close Camera

    1. Stream off the sensor

    2. Hold the reset pin

    3. Power off the sensor

When using the AP1302 ISP, it is necessary to download a specific firmware binary during initialization. The launch time of the camera depends on the size of the binary file. The log provided below illustrates the start-up process of the AP1302 ISP and displays the corresponding launch time.

../../../../_images/sw_yocto_app-dev_camera_ap1302-start-up-time.svg

The presented log provides an overview of the AP1302 ISP start-up process and focuses on the launch time, which primarily measures the duration it takes to transmit the firmware through I2C at a speed of 400KHz.