I've frequently been asked "what computer do you use on your robots?", usually from someone looking at a variety of sub-$100 ARM boards. ARM processors have come a long way, but for a ROS computer, they are not the easiest choice. Austin Hendrix has done a lot of work to get a buildfarm up and running for ARM processors -- but there is still a long way to go and many things will not work "out-of-the-box".
So my choice? Well, it's not under $100, but it is a very fast, fairly low power machine (here, I define low-power in the sub-15W range). The latest generation of Intel NUC (Next Unit of Computing) modules offer quite a few options for small Intel Core-based computers. I'm using the 4th-generation i3-based D34010WYK. This offers quite a bit of compute power for ROS, especially when you consider that early TurtleBots ran on a single-core Atom. I've used 35W TDP i3 processors on a number of mobile manipulation problems and been able to run the OpenNI/OpenNI2-based drivers, the navigation stack and MoveIt! without much difficulty. If you're looking for a bit more processor, there is an i5-based version for $100 more.
|Intel NUC (image from Intel NUC website)|
These computers are sold as either a board (somewhat hard to find for sale) or as a kit which includes the case. Either option requires memory, hard drive and wifi card to be added. My setup is:
- 8GB Crucial Ballistix Sport SODIMM. Whatever you choose, be sure it is 1.35V RAM -- the newer NUC models work ONLY with 1.35V RAM (many modules are 1.5V).
- 120GB Crucial mSATA SSD. Intel offers a larger case version of the NUC that fits a standard 2.5" drive, but the smaller versions only take an mSATA drive.
- Intel 7260 Wireless-AC Card. This card will work best with Ubuntu 14.04, older versions will need an updated kernel (at least 3.13) to get working drivers. No need for antennas as they are already in the case.
These boards take 12-24V DC input, but are probably most efficient at 19V. I'm powering mine off a 12V battery connected to a Pololu 5A Step-Up Regulator that is configured to output the desired 19V. My batteries will never get even close to 19V even when fully charged, and so the regulator should not have any issues.
I would recommend installing Ubuntu 14.04 and using ROS Indigo for these machines. If you want to use an older Ubuntu distro, you should definitely make sure your wifi card is compatible, because the Ethernet port will not work with the drivers present on the 12.04 installer and you will have to connect to ubuntu.com to update somehow. Another alternative is to look for a NUC based on the 3rd-generation Intel Core processors, but these might be hard to locate.