Integration with Raspberry Pi5 : rp1-cfe

cam-epc670 utilizes Raspberry Pi - Image Processing Signal Processor (PiSP) to interract with the host device.

The Raspberry Pi PiSP Camera Front End (rp1-cfe) driver is located under drivers/media/platform/raspberrypi/rp1-cfe. It uses the V4L2 API to register a number of video capture and output devices, the V4L2 subdev API to register subdevices for the CSI-2 received and the FE that connects the video devices in a single media graph realized using the Media Controller (MC) API.

Data Flow

In this setup with RPi5 with PiSP we basically have:

Component

Role

epc670

Generates RAW images with timing, exposure, gain.

CSI-2

Converts CSI-2 packets into pixel words; feeds them reliably into the user space

Memory outputs

V4L2 buffers where frames land for user space

We can think data flow as follows:

[epc670] -> [CSI-2] -> [memory outputs]

Note that further video processing pipelines interface with /dev/video0 and the data does not flow through PiSP FE-BE.

Media Topology

The media topology registered by the rp1-cfe driver is as follows.

Media Topology

Follow steps below to regenerate the figure

Using media-ctl to get the media topology

To graphically view the media topology from the terminal, you can use the media-ctl tool together with Graphviz.

Install the required tools

sudo apt install v4l-utils graphviz

Find the valid media device

Run

v4l2-ctl --list-devices

and note the one which is listed under rp1-cfe (platform:1f00128000.csi)

  • You can also use docker/scripts/media_device.sh. Check the script for details.

Dump the media topology in DOT format

Replace the name <media-device> with the media device you see in step 2.

media-ctl -d <media-device> --print-dot > topology.dot

Render the graph as an image

# Save to svg
dot -Tsvg topology.dot -o topology.svg
# Save to png
dot -Tpng topology.dot -o topology.png