[Peter Johnson]

I've been exploring options for a Linux based robot controller for my own projects. Thoughts so far:

- Gumstix Overo Earth COM processor module (http://www.gumstix.com/store/catalog...roducts_id=211)
- Gumstix Chestnut43 I/O board (http://www.gumstix.com/store/catalog...roducts_id=237)

The Overo Earth has a 600 MHz OMAP3503 processor (ARM Cortex-A8 CPU), and 256 MB of RAM, so it's more powerful and has more memory than the cRIO. It will happily boot off a microSD expansion card (you can get 8-16 GB ones nowadays for cheap). Runs Linux like a champ.

The Chestnut43 board for the Overo provides Ethernet, USB console, and USB host interfaces. Ethernet is perfect to hook up to a wireless bridge, just like the cRIO. It also has a 40-pin expansion port which provides 6 PWMs, an I2C port, 6 A/D input lines, and 2 serial ports. Unfortunately, the expansion port is all 1.8V signals so a breadboard to level shift up to 5V signals is required to make this useful. I've not found something off the shelf to do this yet. It takes a 5V supply input, easy enough to grab off of the FIRST power distribution board, or alternatively you can get a 12V to 5V DC-DC converter pretty cheaply from DigiKey.

One thing I'm considering is designing and having fabricated a custom PCB design to replace the Chestnut43 board that would provide Ethernet, USB, 9-pin RS232, I2C, PWM-style 5V interfaces and be supplied from 12V, resulting in an entire robot controller in a size similar to that of the FIRST digital sidecar (and with similar interfaces, plus Ethernet and some analog inputs). If someone out there is interested in something like this, let me know! Of course, if it already exists, I would be even happier to not have to design it in the first place .

If even more I/O is needed, the UBW32 (http://www.schmalzhaus.com/UBW32/) available from SparkFun has 3.3V and 5V I/O and can serve as a USB slave to the Overo. This is actually powerful enough to be a robot controller on its own, although it's more similar to the old IFI controller than the cRIO (e.g. it's a PIC microcontroller, not Linux capable, etc).