cross-compile ros_comm for ARM9 LPC3250

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I don't know your actual use-case, but for some applications installing and running a full ROS system on your embedded board might not be necessary. I don't have extensive experience with any of these, but I thought I'd mention them as alternatives to the two other answers:

1. rosc (and github.com/synapticon/rosc): should target bare-metal as well as boards with an OS (eg: Linux). More info: ROSCon13 slides.
2. rosserial (in particular: rosserial_embeddedlinux)
3. uROSNode: as the name implies, targeted towards microcontrollers. ROSCon13 slides.
4. cROS (and this ROS blog news post. Some slides from IAS13 here): according to the developers: "an ANSI C library, called cROS, that acts as ROS interface". iirc, there is going to be an open-source version of this, somewhere in Q2-2015 (UPDATE: this has been released. See github.com/it-robotics/cros). Similar in goals to rosc, but (if the marketing slides are to be believed), much closer to being a true and complete client library for embedded systems.

First two are targetting situations in which you don't want to run a full-blown ROS on your embedded device. rosserial does this by implementing a custom bridging protocol, which requires a bridge node running on some host device that does run a 'normal' ROS. rosc on the other hand does not and should allow the embedded device to become a first-class-citizen of a ROS node graph.

The third option mainly targets microcontrollers, but I included it as another example of a pure ANSI C implementation.

Keep in mind though that all of these have in common that they don't allow you to run a ROS master on your embedded device, they are client libraries.

Edit: added cROS info.

Edit2: updated cROS info: it has been released.

Most of my experience is on running a ROS system on networks of workstation-class x86 machines, but if the main issue is building the dependencies, then here's a lists generated by the apt-rdepends tool on the standard core ROS Hydro metapackage for Ubuntu 12.04:

ros-hydro-ros-base dependencies

This list was generated on an Ubuntu 12.04 machine via:

apt-rdepends ros-hydro-ros-base  | grep ")$" | sort | uniq

For the ROS core packages, I wouldn't worry about the kernel 2.6 constraint.

One thing that you should look into for consideration of ROS in the long-term is the ROS 2.0 roadmap, since one of their main focuses is on replacing the current implementation of the ROS TCP/UDP middleware with a DDS-based core.

I know you're not interested in running Ubuntu on your hardware, but Mark Shuttleworth (of Ubuntu) did recently reach out to the ROS core dev team about Ubuntu's work on "Ubuntu Snappy" which is a reworking of Ubuntu meant for embedded systems. I haven't experimented with this, but it might be worth looking into since they've continued to collaborate closely on the project.