Camera interface

2025-08-14T19:10:36Z

SebT:

On this page you will find useful informations on how to use the Camera/CMOS Sensor Interface (CSI/CSI2) of the i.MX chip found on your APF and OPOS93Dev board.
Currently only the [[APF27]], [[APF6]] & [[OPOS93]] are supported.

==Hardware==
===APF27===
* All the signals of the i.MX27 CSI interface can be found on the J9 connector of the [[APF27Dev|APF27Dev development board]].
* You should connect an external camera/sensor compatible with the CSI interface (8bits data bus) to see something ;-). Here are the tested sensor models:
** [[OV9653]] / [[OV9655]]
** [[OV7670]]
** [[OV3640]]
* All these sensors are controllable through an I2C interface. The one on J8 connector of [[APF27Dev]] can for example be used.

===APF6===
* [[APF6Dev]] boards have a wandcam (OV5640) compatible connector (near the PCIexpress one).
* MIPI bus is used on [[APF6Dev]]

===OPOS93===
* The [[OPOS93DEV]] board has a 15-pin Raspberry Pi Camera compatible connector (located below the OPOS93 SoC).
* A 2-lane MIPI CSI-2 bus is used.
* Tested with the OmniVision OV5647 sensor.

==Driver==
* From now we consider that you have a supported camera module plugged on your development board
* CSI interface can be driven through the V4L2 (Video For Linux) standard interface as soon as CSI/MIPI driver is loaded:
{| border="1" cellpadding="10" cellspacing="0" summary="Camera drivers" class="wikitable"
|- style="background:#efefef;" align="center"
! APF27 || APF6 (kernel 3.19+)
|---
|<pre class="apf">
# modprobe mx27_camera
</pre>
* Then you have to load your camera driver in order for him to "attach" to the CSI one (for example for the OV9653):
<pre class="apf">
# modprobe ov96xx
</pre>
|
<pre class="apf">
# modprobe -a mx6-camera mipi-csi2 ov5640-mipi
</pre>
|}

* On OPOS93, the driver is automatically loaded when the camera is connected.
* Now it's up to you to configure your camera with the tools/API the camera driver is offering...

==Test==
* We have a small SDL/V4L2 app to quickly test that your camera is working properly (you will also need a LCD interface): ''target/demos/camera/capture/''
** it may be installed by default on your rootfs depending on your Buildroot defconfig.
** to launch it (here to have a 640x480 camera image on a LW700 TFT):
<pre class="apf">
# capture --width 640 --height 480 --cam_width 640 --cam_height 480
</pre>

* To trigger autofocus (APF6 with 3.19+ kernel):
<pre class="apf">
# v4l2-ctl -c auto_focus_start=1
</pre>

* On OPOS93DEV, the pipeline must have the same configuration on every link in the pipeline.
* Let's create a script:
<pre class="apf">
# cat << EOF >> setCam.sh && chmod +x setCam.sh

SOURCE=$3
FORV4L2=$4
XL=$1
YL=$2

if [[$SOURCE == ""]]; then
SOURCE=SBGGR10_1X10
fi
if [[$FORV4L2 == ""]]; then
FORV4L2=BG10
fi
if [[$XL == ""]]; then
XL=640
YL=480
fi

BAYER=$SOURCE/$XL\x$YL
echo Setting format to $XL/x$YL in $SOURCE - $FORV4L2
media-ctl -v -V "'csidev-4ae00000.csi':0 [fmt:$BAYER field:none]"
media-ctl -v -V "'csidev-4ae00000.csi':1 [fmt:$BAYER field:none]"
media-ctl -v -V "'mxc_isi.0':0 [fmt:$BAYER field:none]"
media-ctl -v -V "'mxc_isi.0':1 [fmt:$BAYER field:none]"
media-ctl -v -V "'crossbar':0 [fmt:$BAYER field:none]"
media-ctl -v -V "'crossbar':2 [fmt:$BAYER field:none]"
media-ctl -v -V "'ov5647 2-0036':0 [fmt:$BAYER field:none]"
media-ctl -l "'ov5647 2-0036':0 -> 'csidev-4ae00000.csi':0[1]"
v4l2-ctl -d /dev/video0 --set-fmt-video=width=$XL,height=$YL,pixelformat=$FORV4L2
v4l2-ctl -d /dev/v4l-subdev3 -c exposure=855
v4l2-ctl -d /dev/v4l-subdev3 -c gain_automatic=1
v4l2-ctl -d /dev/v4l-subdev3 -c auto_exposure=0
v4l2-ctl -d /dev/v4l-subdev3 -c white_balance_automatic=1
> EOF
</pre>

* Run your script (if you put some arguments, remember the entire pipeline must have the same configuration) and check that all pads have the same format.

<pre class="apf">
# .setCam.sh
# media-ctl -p
</pre>

* Try streaming to the framebuffer.
<pre class="apf">
# gst-launch-1.0 --no-position v4l2src ! 'video/x-bayer,format=bggr10le,width=640,height=480,bpp=10,framerate=(fraction)10/1' ! bayer2rgbneon reduce-bpp=t show-fps=t silent=t ! fbdevsink device=/dev/fb0
</pre>

==Going further==
* [[Using the i.MX27 video codec|Using the i.MX27 video codec]]

==Links==
* [http://linux.bytesex.org/v4l2/ Video4Linux]

[[Category:Vision]]

ArmadeusWiki - User contributions [en]

Camera interface