CaspaPX

The MT9V032 sensor at the heart off the CaspaPX is not yet supported in the kernel, so a little work is necessary to get the camera up and running.

The OMAP35X processors have dedicated hardware for capturing and processing data from image sensors. The CaspaPX camera sensor outputs raw 10-bit Bayer images which is transfered to the Image Signal Processor (ISP) via a parallel interface. The ISP contains various submodules that can be exported as V4L2 devices in /dev. For additional hardware information see the external links section.

TODO: include a photo taken with the camera

Quickstart

The first steps are important to verify your hardware setup and to test your customizations later.

Install Pre-built Kernel

The easiest way to get started is to replace the kernel and modules of an existing image. This method was tested on an Overo Fire with a Tobi expansion board using the desktop image available here.

Get the kernel and modules.

$ mkdir ~/caspakernel
$ cd ~/caspakernel
$ wget cumulus.gumstix.org/images/caspapx/uImage
$ wget cumulus.gumstix.org/images/caspapx/lib.tar.gz

Extract the modules.

$ tar -xf lib.tar.gz

Copy them to an Overo already running the image that you want.

$ scp lib/* root@overo:/lib/
$ scp uImage root@overo:/boot/uImage;
$ scp uImage root@overo:/media/mmcblk0p1/uImage

Reset the overo.

$ ssh root@overo 'shutdown -r now'

This method is especially convenient for making modifications to the driver or kernel. See the customization section for more information.

Test

From the serial console:

# export -DISPLAY :0.0

# gst-launch v4l2src ! xvimagesink
<or>
# mplayer tv:// -tv driver=v4l2:device=/dev/video0

From the desktop:

<left-click on desktop> Applications > Multimedia > Cheese

Bitbake

TODO: make a recipe, give the command to build it here and link to an article about creating/modifying recipes

Customization

This section describes how to customize the camera driver and kernel for your needs.

2.6.34

Get the kernel source that is used in the Gumstix kernel recipe (~/overo-oe/org.openmebedded.dev/recipes/linux/linux-omap3_2.6.34.bb) and create a new branch from the recipe SRCREV.

$ cd ~
$ git clone git://www.sakoman.com/git/linux-omap-2.6.git
$ cd linux-omap-2.6
$ git checkout -b 2.6.34 cb89736af28f583598e49a05249334a194d00f1d

Get the patch

$ wget http://cumulus.gumstix.org/sources/mt9v032-2.6.34.patch
$ patch -p1 < mt9v032-2.6.34.patch

Make a copy of the default kernel configuration to use as a starting point for your customizations.

$ cp ~/overo-oe/org.openembedded.dev/recipes/linux/linux-omap3-2.6.34/overo/defconfig ./
$ cp defconfig .config

Add the cross compiler to your path and configure the kernel

$ export PATH=/home/username/overo-oe/tmp/sysroots/i686-linux/usr/armv7a/bin:${PATH}
$ make ARCH=arm menuconfig

Ensure that the following modules are enabled

-> System Type
 -> OMAP34xx Based System 
-> Device Drivers
 -> Multimedia support (must be built-in)
  -> Video For Linux (must be built-in)
  -> Video capture adapters (must be built-in)
   -> SoC camera support
    -> OMAP 3 Camera support
    -> mt9v032 support

Build kernel and modules

$ make ARCH=arm CROSS_COMPILE=arm-angstrom-linux-gnueabi- uImage
$ make ARCH=arm CROSS_COMPILE=arm-angstrom-linux-gnueabi- modules

Install modules

$ mkdir ~/linux-omap-2.6/modules
$ make ARCH=arm CROSS_COMPILE=arm-angstrom-linux-gnueabi- INSTALL_MOD_PATH=./modules modules_install

Other Kernel Versions

The ISP code used for the 2.6.34 patch came from the arago-project. This is the OMAP3 PSP kernel integration/staging tree

$ git remote add git://arago-project.org/git/projects/linux-omap3.git aragoOMAP3 PSP kernel integration/staging tree
$ git fetch arago
$ git checkout -b arago

The V4L2 subdevice framework offers a way to configure the Image Signal Processor pipeline from userspace. This is currently under active development and users wishing to make use of this should visit the Media controller development repository here. This contains the bleeding edge Video for Linux media framework, ISP, and MT9V032 drivers.

MT9V032 Driver

If you want to take advantage of an unimplemented sensor feature, change defaults, etc., you need to modify the driver source. First, make sure that you change your kernel configuration to build the MT9V032 as a module unless you're only making a minor change. This will allow you to test your changes

Here is a convenient script for updating the driver after you've made a change:

#! /bin/bash 

make -j8 ARCH=arm CROSS_COMPILE=arm-angstrom-linux-gnueabi- modules;
scp drivers/media/video/mt9v032.ko root@10.0.1.15:/lib/modules/2.6.34/kernel/drivers/media/video/
ssh root@overo 'rmmod mt9v032; modprobe mt9v032'

Image Signal Processor

There is some code that you can't modularize and modifying means rebuilding the kernel. Such is the case for the ISP code which is used by board-overo.c for hardware configuration. Another script like that in the previous section can be very useful.

This script rebuilds the kernel, copies it to the COM, and resets:

#! /bin/bash 

make -j8 ARCH=arm CROSS_COMPILE=arm-angstrom-linux-gnueabi- uImage;
scp arch/arm/boot/uImage root@10.0.1.15:/boot/uImage;
scp arch/arm/boot/uImage root@10.0.1.15:/media/mmcblk0p1/uImage
ssh root@10.0.1.15 'shutdown -r now'

TODO: discuss where previewer constants are and how they affect the output image

External Links

OMAP35x Technical Reference Manual

MT9V032 Datasheet

CaspaPX CAD files