Frankly, there was an element of luck required to figure out how to get the Raspberry Pi camera working under Ubuntu. The reason why is described below.
The raspicam node uses the Raspbery Pi video camera interface API (Application Programming Interface) to access the image data. The Raspberry Pi camera is actually connected to the GPU (Graphics Processing Unit) where specialized graphics processing units can manipulate the image before it is forwarded on to the main ARM7 cores. The Raspberry Pi GPU is closed source proprietary code is only shipped as a binary blob that is loaded into the GPU at processor boot up time.
In general, the Raspberry Pi camera is fully supported by
the Raspberry Pi foundation. However, in order to support
their older products (the model A, model B, and model B+),
they have had to develop (with user help) their own Linux
distribution called Raspian. The Raspberry Pi camera is
fully supported by the Raspian Linux distribution.
ROS is only supported by the Ubuntu Linux distribution.
Since the raspicam_node is for ROS, it must be run on
a Ubuntu Linux distribution. While the Ubuntu Linux distribution
is not fully supported by the Raspberry Pi Foundation,
the Raspberry Pi foundation is actually OK with the Ubuntu
Linux distribution and does provide some limited support.
Both the Ubuntu and Raspian distributions use the same packaging system called Debian Packages. To make things confusing, the Raspian Linux distribution is based on the Debian Linux distribution. While the debian package formats are the same between both the Ubuntu and Raspian Linux distributions, the underlaying Debian packages are NOT 100% inter-operable. Sometimes the Ubuntu Linux distribution installs files in a different location than the Raspian distribution does. This is great fun.
There are two ways that firmware is provided to the Raspberry Pi.
There is a package called raspberrypi-bootloader-nokernel which
provides the binary blob and there is a program called rpi-update
that can do so as well. The bootloader stuff tends to be older
than the rpi-update method.
After compiling userland using the buildme script, the
raspicam_node code compiles without errors. When the
raspicam_node was first run it failed. After running the
rpi-update program it worked for a while. As other people
tryed to install raspicam_node, it simply did not work.
After much sleuthing it became clear that the Raspberry Pi
foundation had accidentally checked in a firmware version that
did not work.
Our temporary solution is to use slightly older firmware,
until whatever problem that caused raspicam_node to not work,
to start working again.
It was a small miracle is that there was a small window were we figured out the firmware worked, and we managed to find that window. Once we figured out that it was firmware, we were on solid ground to finding a work around. Initially we used the command below:
sudo rpi-update cad980c560b6c240fdaf6cb4b7703921b18114e3
to install a specific firmware that worked. These days, the latest released firmware version is used, because it works. So, we no longer explicitly specify the firmware version.
The raspicam_node for ROS is available on our github. https://github.com/UbiquityRobotics/raspicam_node
If you are curious about firmware revision numbers, there is a post about them.