
userial is an Free project building an USB to I2C/SPI/GPIO bridge, using the Atmel AT90USB647 chip. Hardware and Software are released under an Open Source licence. It supports the following interfaces:
The board communicates with the host computer using a CDC (USB communications device class). This makes it easy to use userial without installing a device driver or special libraries. Due to the ASCII based command interface it is easy to control devices manually with just a terminal emulation. This makes it easy to obtain quick results, to configure devices on-the-fly or to control prototyping boards in a straight-forward way.
Schematics and firmware are available to the public. The firmware is released under the terms of the MIT license and the hardware is released under the terms of the Creative Commons Attribution-Share Alike 3.0 Unported License.
If you don't want to build your own hardware, then you might find the bumble-b board from Fletchtronics worth a look. It is a rather inexpensive board based on the AT90USB162 chip and supports userial firmware. (Please search in the fletchtronics website for the firmware. I plan to support the bumble-b board in the next firmware release.)
All news can be read in the userial news archive.